What is Quantum Biology?

The essence of quantum biology, according to Filippo Caruso.

The essence of quantum biology, according to Filippo Caruso.

The beauty of Physics is mainly represented by its remarkable capability to understand any fascinating natural phenomena, from the origin of rainbows to the formation of a star, from the blue color of the sea to the changing seasons, and even the basic functioning of man-made objects and techniques such as lasers, barcodes, smartphones, computers, GPS, LEDs, transportation systems, etc., which all of us heavily use in our everyday lives. That’s why physics can be seen as the foundation of many disciplines of science and also allows to understand and solve completely different problems in other fields including, among others, medicine, biology, engineering, and social sciences. It basically consists of two branches that focus on the macroscopic and microscopic world: They are called classical and quantum physics, respectively. To test and apply the latter, one usually needs to go to very sophisticated and expensive labs that make it possible to observe the fragile properties of very tiny objects like atoms and electrons or to engineer complex but very clean nanostructrures which is often only possible at temperatures that are much colder than any place on Earth. However, recent experimental and theoretical studies have shown that “hot and wet” natural macroscopic phenomena like photosynthesis, olfaction and bird navigation can be investigated remarkably well through quantum physics.

Fascinating ultra-fast laser spectroscopy experiments on photosynthesis have investigated the electronic energy transfer from the antenna complex, where the light is absorbed, to the so-called reaction center, where the electronic energy is converted into chemical energy that is further exploited for the life of bacteria, algae and green plants. This transport process occurs along a molecular wire, represented by a nanoscale pigment-protein complex, similarly to a standard TV cable from a roof antenna to our indoor TV devices. However, for some biological light-harvesting systems the amount of signal (light) to be absorbed from the antenna is extremely low, hence they really need to optimize this energy conversion task as well as possible to survive.

The prototype system for these studies is the so-called Green-Sulphur bacterium that is a main candidate for being the progenitor of life on our planet. It is assumed to exist on Earth for 3-4 billion years already. This bacterium lives also on the bottom of the ocean at a depth of 5000 meters where no sunlight is detected at all. However, it lives off the dim glow of hydrothermal vents coming from chimney-like structures that are called black smokers. In other words, it absorbs the geothermal energy generated and stored in the Earth even though this corresponds to a very tiny amount of light radiation. In fact, each bacterium absorbs around 3 photons per second while each of its pigment-protein structures, called a Fenna-Matthews-Olson (FMO) complex, receives around 1 photon every 24 hours. In comparison, let us point out that a plant leaf absorbs a figure around 1 followed by 24 zeros of photons. In time scale, the bacterium would have to live for the age of the universe to receive the same amount of light that a leaf does in less than one microsecond. Therefore, each FMO complex has to successfully convert its single daily photon into available energy to survive and to have guaranteed the origin of life on Earth. Hence, this energy transport occurs in just 5ps and with a very remarkable efficiency of almost 100% that is very surprising since these are ‘hot and wet’ biological objects.


Quantum physics seemingly hold the secret to the remarkable efficiency of photosynthesis. Photo: iStock.com/EOPITZ

Quantum physics seemingly hold the secret to the remarkable efficiency of photosynthesis. Photo: iStock.com/EOPITZ

In 2007, ultra-fast laser spectroscopy experiments by Fleming et al. have demonstrated that these phenomena need quantum physics to be explained, since the traditional classical physics (Forster) theory does not fit the observed data. In 2008, the second surprise came from theoretical studies by Plenio, Huelga, Caruso, Aspuru-Guzik, Lloyd et al. showing that quantum coherence is not enough to reproduce the measured 100% efficiency while another important ingredient is represented by the environmental “disturbance” (noise), here mainly represented by the thermal random vibrations of the external protein scaffolding. Indeed, without noise one obtains an efficiency of 50%, while with noise one gets 100%. It turns out that the external protein structure not only protects the internal quantum coherence for a time scale about 100 times longer than the expected one, but also adds some amount of noise to optimize the energy transfer task. Therefore, we have demonstrated that the interplay between quantum coherence and the unavoidable external environmental noise plays a crucial role in the performance of bio-molecular complexes. This can be intuitively explained by the fact that, on one side, quantum coherence allows the system to explore several network paths in parallel to achieve the desired task, while, on the other, noise is a key ingredient both to protect the fragile property of coherence and, more importantly, to find the optimal solution and leave out inefficient slower pathways.

These works gave rise to the very recent but rapidly developing research field, nowadays known as Quantum Biology, investigating the role of quantum effects in biological systems. The other two main topics of this field are given by bird navigation and quantum smell, where similar quantum phenomena have been proposed and observed.

Regarding the first one, there is evidence by Schulten, Ritz et al. proposing that many animals including birds like European Robins exploit a very fragile quantum property, called entanglement, for long-distance navigation based on the relative orientation with respect to the Earth’s magnetic field direction. More surprisingly, they are able to keep such entanglement in their eyes, at room temperature, for a time scale (tens of microseconds) that lasts even longer than the most advanced (often even ultra-cold) laboratory setups. In particular, this feature does trigger different chemical products inside a protein, named as cryptochrome, depending on the external magnetic field, hence providing a chemical compass. Then, this would allow the bird to create a map of the Earth’s magnetic field. Supporting this hypothesis, Ritz’s experiments have shown that by artificially adding an extra very weak magnetic field the bird orientation is affected, and this may only happen through a very sensitive quantum nanodevice: This is remarkably interesting.


European Robins make use of quantum entanglement for navigation.  Photo: iStock.com/kart31

European Robins make use of quantum entanglement for navigation. Photo: iStock.com/kart31

Olfaction is traditionally explained in terms of a shape theory or “lock and key” model (Moncrieff, 1949), i.e. we smell a particular odour when both shapes of the odorant molecule and of the corresponding receptor (inside the nose) perfectly fit each other. Then, our sense of smell would depend only on the shapes of molecules we sniff in the air. However, a controversial theory, first developed by Dyson in 1927, has been further developed by Turin in 1990 (swipe card model) after observing via fruit fly behavioral experiments that molecules with the same shapes (with hydrogen atoms replaced by deuterium) correspond to completely different smells (going from perfumes to rotten eggs). However, these molecules show quite different vibrations. Indeed, molecules vibrate as collections of atoms on springs oscillating at a given frequency (a quantum). Then, in presence of a particular “smelly” molecule, an electron within a smell receptor in the nose can “jump” (tunnel through a barrier) across it, bringing a quantum of energy into one of the odorant’s bonds, hence “activating” a resonant “spring” (like sort of a FM radio tuning). In physics, this specific quantum phenomenon is called inelastic electron tunneling, i.e. the nose behaves as a scanning tunneling microscope.

These fascinating experimental and theoretical discoveries may lead to a better understanding of biological systems but also to more efficient and robust innovative quantum technologies for solar energy, communication, and navigation that are fundamental in our everyday lives. For instance, more people should know that ultra-fast spectroscopy has allowed us to show that in the first step of photosynthesis the light harvesting process occurs in a picosecond time scale and with the incredible efficiency of 99% thanks to quantum features, so why shouldn’t we learn from what Nature has been doing very well for billions of years?

Finally, a deeper understanding of biological natural phenomena might also bring a clear impact on society’s consumption of energy and the development of innovative, bio-inspired, more sustainable and cheaper technologies going much beyond our current state-of-the-art. Then we should learn from what Nature has been doing very well for so many years, and engineer new nanomaterials that are able to exploit the same physical principles to perform some tasks with a remarkably high efficiency and robustness, e.g. the light harvesting process in a novel bio-inspired solar cell or more sensitive magnetic/olfaction nanosensors. However, there are still several open questions in the actual ultimate role of quantum physics in the specific proteins involved in such natural phenomena, and about how, for example, optimal control techniques and manipulation schemes, which have been developed for other quantum systems, may further exploit these effects. By doing so, we believe the latter will be successfully converted into more feasible, robust and very efficient devices for green energies, communication and navigation protocols, biological sensing and imaging, with all being based on more environment-friendly sustainable resources.


What's the smell of

What’s the smell of “Eureka!”? Photo: iStock.com/Imagesbybarbara

Jenseits des Standardmodells: Sterile Neutrinos und Dunkle Materie

Dass ich erkenne, was die Welt im Innersten zusammenhält.

Von diesem Wunsch getrieben hätte Goethes Faust sicher Gefallen am heutigen Standardmodell der Teilchenphysik gefunden: Es beschreibt die fundamentalen Bausteine der uns umgebenden Materie und auch ihre grundlegenden Wechselwirkungen untereinander. So hilft es uns zu verstehen, wie sich aus den Grundbausteinen immer komplexer werdende Strukturen ergeben -von Nukleonen, Atomkern und -hülle bis hin zu hochkomplizierten Molekülen.

In seiner Vorhersagekraft ist das Standardmodell der Teilchenphysik herausragend: Ein ganzes Kaleidoskop von fundamentalen Teilchen wurde in der Entwicklung des Standardmodells vorhergesagt und später experimentell bestätigt. Den vorläufigen Abschluss fand diese Suche im Jahre 2012, als am Large Hadron Collider (LHC) der lang ersehnte, letzte fehlende Baustein des Standardmodells gefunden wurde – das Higgs-Boson. Für dessen Vorhersage vor etwa 50 Jahren wurde Peter Higgs und François Englert der Nobelpreis für Physik 2013 verliehen.

Aber nicht nur qualitativ, sondern auch quantitativ ist das Standardmodell beeindruckend: In der sogenannten Quantenelektrodynamik, einem Teilgebiet des Standardmodells, können bestimmte im Labor sehr genau messbare Eigenschaften von Teilchen mit einer relativen Genauigkeit von 10-9 erklärt werden, also einer Abweichung von 1:!

Auch wenn das Standardmodell eine sehr erfolgreiche Theorie ist, so wissen wir – ganz wie Doktor Faust – dass unser Wissen unvollständig ist: Die Suche nach den innersten Bausteinen und Kräften unseres Kosmos ist noch nicht beendet. Denn inzwischen haben wir eine lange Liste an Beobachtungen, die im Standardmodell nicht erklärbar sind. Es kann also nur eine effektive Teilbeschreibung eines umfassenderen Modells sein.


François Englert 2015 in Lindau. Foto: R. Schultes/Lindau Nobel Laureate Meetings

François Englert 2015 in Lindau. Foto: R. Schultes/Lindau Nobel Laureate Meetings


 Dunkle Materie und unentschlossene Neutrinos

Solche Phänomene, die nicht ins Standardmodell passen, werden im Physikerjargon ‘Beyond Standard Model’ oder einfach nur ‘BSM’ genannt. Zwei Phänomene sind meiner Ansicht nach besonders interessant:


1. Dunkle Materie.

Dunkle Materie heißt so, weil wir sie nicht sehen können, und zwar weder mit elektromagnetischer Strahlung im sichtbaren Bereich, noch in anderen Wellenlängenbereichen, die uns heute dank technischer Erweiterung unserer Augen zur Verfügung stehen. Nun wird man sich berechtigterweise fragen, warum Physiker an Materie glauben, die sie nicht sehen können.

Für Dunkle Materie gibt es einen erschlagenden Katalog an Hinweisen, der in jedem Indizienprozess überzeugen würde. All diese Indizien beruhen darauf, dass Masse Gravitation verursacht.

So beobachtet man etwa, dass sich Spiralgalaxien – wie auch unsere Milchstraße – zu schnell um sich selbst drehen. Diese Mechanik, die im Grunde den gleichen Gesetzen folgt wie die Rotation des Mondes um die Erde oder der Erde um die Sonne, ist nicht alleine durch die Anziehungskraft der sichtbaren Masse in der Galaxie erklärbar. Aber auch auf anderen Längenskalen im Universum macht man Beobachtungen, die die gleichen Schlüsse über die Existenz und Häufigkeit der Dunklen Materie zulassen: Wir wissen, dass die sichtbare Materie etwa 5% der Energie im Universum ausmacht, Dunkle Materie jedoch 20%. Die restlichen 75% sind Dunkle Energie, ein weiteres Phänomen ‘BSM’; ein Thema für sich.

Da das Standardmodell jedoch keinen passablen Kandidaten für die Dunkle Materie liefert, welcher alle Anforderungen erfüllen würde, muss es unvollständig sein.


2. Neutrinooszillationen.

Neutrinos und ihre Antiteilchen, die Antineutrinos, sind elektrisch neutrale Elementarteilchen. Auch sie wurden vor etwa 85 Jahren zunächst theoretisch vorhergesagt und dann deutlich später experimentell bestätigt. Wir wissen, dass Neutrinos in drei Varianten vorkommen: Es gibt Elektron-, Myon- und Tau-Neutrinos, und jeweils das passende Antineutrino dazu.

Neutrinos spielen bei vielen Kernprozessen eine Rolle, also zum Beispiel bei der Kernfusion in der Sonne oder bei der Kernspaltung in Reaktoren. Der Reaktor in einem durchschnittlichen Kernkraftwerk erzeugt in etwa zehn Trilliarden Antineutrinos pro Sekunde, während die Sonne nochmals um viele Größenordnungen mehr davon produziert. Im Kernreaktor werden Elektron-Antineutrinos erzeugt. Nach ihrer Geburt verlassen die Neutrinos mit nahezu Lichtgeschwindigkeit den Reaktorkern, da sie nur sehr schwach mit der Reaktorhülle interagieren, und daher quasi nicht gestoppt werden können.

Mit großen und hochsensiblen Detektoren lassen sich jedoch ein paar Neutrinos in einiger Entfernung nachweisen. Dabei stellt man fest, dass sich Elektron-Antineutrinos während ihrer Reise in Myon- und Tau-Antineutrinos umgewandelt haben. Diese Beobachtung ist unter dem Namen ‘Neutrino-Oszillationen’ bekannt und lässt darauf schließen, dass Neutrinos eine Masse haben. Für ihre Arbeit an entsprechenden Experimenten erhielten Arthur McDonald und Takaaki Kajita 2015 den Nobelpreis für Physik.

Dass Elementarteilchen eine Masse haben, ist prinzipiell durch den Higgs-Mechanismus verstanden worden. Das Besondere an der Masse der Neutrinos ist nun, dass ihre Masse laut Standardmodell eigentlich gleich null sein müsste. Diese Aussage beruht auf dem absoluten Grundpfeiler des Standardmodells, der sogenannten Eichinvarianz. Dieses Prinzip besagt anschaulich, dass physikalische Realitäten sich nicht ändern dürfen, wenn verschiedene gedachte Beobachter im Universum lokal einen anderen ‘Maßstab’ wählen. Schließlich ist auch die Entfernung von Berlin nach London immer die gleiche, ob man nun in Kilometern, Meilen oder Lichtjahren messen will. Auch hier wird wieder deutlich, dass das Standardmodell nicht der Weisheit letzter Schluss sein kann.


Das kosmische Spinnennetz

Nun ist es offensichtlich, dass das Standardmodell erweitert bzw. verändert werden muss, um diese Beobachtungen hinreichend zu erklären. Und was liegt dabei näher als der Versuch, möglichst viele neue Phänomene mit möglichst wenig neuer Theorie zu erklären?

So beschäftigt sich die Arbeitsgruppe von Dr. Georg Raffelt am Max-Planck-Institut für Physik in München, der ich seit August 2014 angehöre, unter anderem mit Modellen, die sowohl die Neutrinomasse als auch die Frage nach der Art der Dunklen Materie gleichzeitig angehen. Dazu postulieren wir weitere Arten von Neutrinos, welche das ganze Budget an Dunkler Materie im Universum bereitstellen könnten. Diese neuen Neutrinos werden sterile Neutrinos genannt, da sie selbst im Vergleich zu den bekannten Neutrinos (aktive Neutrinos genannt), nur sehr schwach mit dem Rest des Standardmodells wechselwirken.

Eine gute Theorie sollte testbare, im Zweifel widerlegbare Vorhersagen liefern. So sollte sie in unserem Falle etwa erklären, wie die sterilen Neutrinos in der Frühzeit des Universums entstanden sind und ob die Vorhersagen aus diesem Geburtsprozess mit den heutigen Gegebenheiten im Kosmos übereinstimmen.

Eine für unsere Arbeit sehr wichtige Anforderung ist die sogenannte kosmische Strukturbildung. Aus der Messung der kosmischen Hintergrundstrahlung – Nobelpreise 1978 (Arno Penzias und Robert Woodrow Wilson) sowie 2006 (George Smoot und John Cromwell Mather) – wissen wir, dass das Universum etwa 380.000 Jahre nach dem Urknall sehr homogen war. Die Materiedichte war also überall gleich, Schwankungen waren von der Größenordnungen von 1:100.000 und somit minimal. Das heutige zeichnet sich Universum jedoch durch sehr hohen Dichteunterschiede aus: Galaxien als relativ dichte Objekte gruppieren sich wiederum zu Galaxienhaufen und -superhaufen. Diese Strukturen durchspannen den Kosmos wie eine Art Spinnennetz, und dazwischen ist nichts als unvorstellbar viel leerer Raum.


Evolution der großskaligen Strukturen im Universum von frühen Zeiten (links) zum heutigen Zustand (rechts). Der Ausschnitt entspricht einer Längenskala von etwa dem 5000-fachen Durchmesser der Milchstraße. Deutlich zu erkennen ist die Bildung von spinnennetzartigen Strukturen. Credit: Volker Springel/Max-Planck-Institute for Astrophysics

Evolution der großskaligen Strukturen im Universum von frühen Zeiten (links) zum heutigen Zustand (rechts). Der Ausschnitt entspricht einer Längenskala von etwa dem 5000-fachen Durchmesser der Milchstraße. Deutlich zu erkennen ist die Bildung von spinnennetzartigen Strukturen. Credit: Volker Springel/Max-Planck-Institute for Astrophysics

Die Entwicklung dieser Strukturen wurde durch die Dunkle Materie angestoßen, die durch ihre eigene Gravitation kleine Dichteschwankungen über die Zeit verstärken konnte: Wo ein bisschen mehr Materie war als im Durchschnitt, war auch die Gravitation ein bisschen stärker als in weniger dichten Gebieten. Dadurch wurde noch mehr Masse dorthin gezogen, was den Effekt wiederum verstärkte usw. Dieser kosmische Matthäuseffekt war die Grundlage für die heute vorhandenen Strukturen von Galaxien und Galaxienhaufen.

Dabei ist die Geschwindigkeit der Dunklen Materie im frühen Kosmos entscheidend: Ist sie zu schnell, kann sie die überdichten Regionen schnell verlassen, die Dichteschwankungen schaukeln sich nicht so stark auf. Folglich entstehen weniger kosmische Strukturen, die heute durch die Rotverschiebung der Emissionslinien von Wasserstoff sehr gut kartiert werden können. Durch den Vergleich von Simulationen und Beobachtungen lassen sich somit die freien Parameter unserer Theorie eingrenzen.


What’s next?

Neben der genannten Theorie gibt es noch viele andere Versuche, die Physik jenseits des Standardmodells zu erklären. Um in Zukunft möglichst viele Theorien zu widerlegen und der bestmöglichen Beschreibung unseres Kosmos einen Schritt näher zu kommen, werden derzeit neben den theoretischen viele experimentelle Anstrengungen unternommen: Neue Neutrinodetektoren für bessere Oszillationsexperimente, aber auch bessere Detektoren, die Dunkle Materie im Labor nachweisen sollen, sind weltweit in Betrieb oder in Planung. Nicht zuletzt soll natürlich auch der LHC neue Einsichten in die Teilchenphysik liefern.

Auch wenn es noch völlig offen ist, in welche Richtung die Teilchenphysik das Standardmodell erweitern muss, so ist eine Vorhersage doch sicher: Es bleibt spannend!

Science in Ancient Egypt & Today: Connecting Eras

Thoth, the ibis-headed god of science & wisdom in the ancient Egyptian pantheon. Photo: iStock.com/Kevin Rygh Creative Arts & Design

Thoth, the ibis-headed god of science & wisdom in the ancient Egyptian pantheon. Photo: iStock.com/Kevin Rygh Creative Arts & Design

Science is the seed to plant civilizations and to write history. This is exactly what the Ancient Egyptians realized 5,000 years ago in order to build their own civilization. Realizing the importance of science, Ancient Egyptians believed there is a god of science called T-hoth. Thoth’s body had human form but his head was the one of an ibis. His feminine counterpart was called Seshat and his wife was Ma’at. To show the importance of science in this bygone era and to show how strongly the Ancient Egyptians believed in the interconnection between different scientific fields with focus on specific disciplines and inventions, we will sail along the banks of the River Nile discovering parts of Ancient Egyptian history and how science has affected it.

The god Ra was considered the god of all gods and the second one to rule the world in Ancient Egypt. Surprisingly, Ra was the god of the sun! The sun for Ancient Egyptians was the symbol of power and life and the god of the sun was considered the king of the world. Thoth, the god of science, was the secretary and counselor of the god “Ra” due to the importance of science in this era. Not only that, but Thoth also married Ra’s daughter Ma’at.

Thoth became credited by the Ancient Egyptians as the god of wisdom, magic, the inventor of writing, the development of science and the judgment of the dead. Without his words, the Egyptians believed, the gods would not exist. His power was unlimited in the underworld and rivalled that of Ra sometimes. In the Coptic calendar nowadays, the first month is named after Thoth and known as Tout. It lies between 11 September and 10 October of the Gregorian calendar. Interestingly, Ma’at was the representative of moral and physical law. Some scholars considered her as the most important goddess of Ancient Egypt. While Ancient Egypt is sometimes rather associated with mummies and pyramids, a great number of ancient Egyptian inventions are still being used in our daily lives. Let’s focus on eight of the most important fields for us nowadays.


  • Paper and writing: Ancient Egyptians were among the first civilizations to make widespread use of the invention of writing and to keeping records of events. The earliest form of writing in Egypt was in the form of the hieroglyphics language, which consisted simply of drawings portraying a story. Papyrus was the first form of durable sheets of paper to write on. The material was named “papyrus” as it was made from the papyrus plant. To complete the writing process, one of the inventions in Egypt was, surprisingly, black ink. They were very talented at creating not only black ink, but many multi-colored types of ink and dye. The brilliant colors can still be seen today, thousands of years later.
  • Time: The Ancient Egyptian calendar was originally based on the cycle of the star Sirius, effectively applying astronomy principles to develop an accurate calendar divided into 12 months, 365 days and 24-hour units. We still use their calendar model in our tracking of the days today. They were one of the first to divide days into equal parts through the use of timekeeping devices like sundials, shadow clocks and obelisks with evidences for even water clocks. Generally, the passing of the day was determined by the position of the sun, and the passing of the night was determined by the rise and fall of the stars.
  • Construction: The Ancient Egyptians are known for their massive constructions and outstanding architecture such as the Great Pyramid of Giza, which is one of the Seven Wonders of the World. The ramp and the lever were two of the most famous construction inventions they developed, and the principles that guided them are still widely used in construction today.
  • Ships and Navigation: Trade was an important part of ancient cultures, so having working ships was extremely important. The ancient Egyptians employed knowledge of the science of aerodynamics in their ship construction processes to create ships that were able to catch the wind and push vessels through water. They also developed the concept of using rope trusses strengthening the beams of their ships. They were also the first ones to use stem-mounted rudders on their ships. At first, they built small boats out of papyrus reed but eventually they began building larger ships from cedar wood.


Papyrus reeds on the banks of the mighty river Nile. Photo: iStock.com/© JoLin

Papyrus reeds on the banks of the mighty river Nile. Photo: iStock.com/© JoLin

  • Medicine: Many of their most famous inventions were based upon the scientific principles the Ancient Egyptians discovered. They had a variety of medical techniques and cures for both humans and animals, along with a vast knowledge of anatomy, as they practiced mummification and preservation of the dead. One of the earliest accounts of medical texts originated in ancient Egypt: It described and analyzed the brain, providing the earliest insight into neuroscience.
  • Cosmetics: Many people are not aware that toothpaste was actually an invention of Ancient Egyptians. As their bread had so much grit and sand in it, they experienced problems with their teeth. They invented the toothbrush and toothpaste in order to care for their teeth and keep them clean of grit and sand. The first toothpaste was made of a wide variety of ingredients, some included eggshells, ashes and ground-up ox hooves. Not only that, but they also invented breath mints to cover bad breath. The mints were made of myrhh, frankincense and cinnamon that were boiled in honey and shaped into small bite-sized pellets.
  • Make-up: Make-up originated with ancient Egyptians, where men and women both used to put it on. While the make-up was used primarily for cosmetic purposes and as a fashion statement, it had another advantage as well, in that it protected their skin from the sun. Perhaps the makeup that they are most popular for was the dark kohl that they put around their eyes. Kohl was made from soot and other minerals and is the concept from which modern eyeliner originated.
  • Mathematics: The great pyramids that the ancient Egyptians built required extensive knowledge of mathematics, especially of geometry. Math and numbers were used to record business transactions and the Ancient Egyptians even developed a decimal system. All their numbers were factors of 10, such as 1, 10, 100 and so on. Therefore, in order to denote 4 units, they would write the number “1” four times. The beauty of their development in mathematical science is especially noticeable in one of their monuments that is still awe-inspiring until this very day – The Temple of Abu Simbel in Aswan, Southern Egypt. The sun becomes perpendicular on the face of the statue of King Ramses II (one of the historical Ancient Egyptian kings) inside the temple only twice a year; on October 22 and February 22. Surprisingly, these two days turned to be the king’s birthday and his coronation day respectively. The Sun first enters from the front side of the temple to a distance of 200 meters reaching the Holy of Holies, which includes a statue of Ramses II, surrounded by statues of two sun gods; Ra-Hor and Amun-Ra and the Sun then stays perpendicular on the King’s face for 20 minutes. Interestingly, there’s one statue in the temple that the sun never touches: The statue of the god Ptah, who was considered the god of darkness. This is called the solar phenomenon in Abu Simbel temple.



The temple of Abu Simbel not only impresses through its appearance but also through its mathematical intricacies. Photo: iStock.com/Waupee

The list of wondrous achievements continues, some even speculate that the Ancient Egyptians already possessed some knowledge of electrical phenomena. Lightning and interaction with electric fish was recorded within an Ancient Egyptian text referring to “high poles covered with copper plates” that some believe to be an early reference to electric principles. Inspired by the solar phenomenon and the power of the sun, combined with mathematics and the ancient trials to discover electricity, my research work is dedicated to solar energy and its conversion to electricity. In an attempt to refocus onto the importance of the sun as a clean and everlasting source of energy in order to satisfy one of the basic needs of modern life – generating electricity – my research is based on converting solar energy to electricity or what is called the “photovoltaic effect”. In my research, I work on fabricating solar cells based on thin film absorbers that have the potential of achieving higher efficiencies at lower costs. As Ancient Egyptians were talented in using chemicals for mummification, I am using some chemical compounds based on Copper, Indium, Gallium and Selenium (CIGSe) to fabricate thin film solar cell absorbers that are characterized with a high absorption coefficient leading to high efficiencies of conversion. These absorbers are hundred times thinner semiconductors compared to Silicon wafers (current state-of-the-art technology) with lower energy needs and simpler preparation methods. Solar cells based on these absorbers with other high band gap absorber materials that I invented consisting of Copper, Silicon and Sulfur (CSiS) could be able to form a multi-junction solar cell breaking current records of efficiencies especially if equipped with a solar tracking system.

Organic Electronics: Coming soon to a Farmer’s Market near you?

One of my favorite scenes from Harry Potter is when Harry receives a gift from Hagrid, a wonderful photo album filled with moving images of his parents smiling and waving at him, and the first thought that came to my mind was ”Is someone working on that?” I know that the boundaries of science have already been tried and tested enough by the fascinating world of science fiction, and we don’t need fantasy doing it now, but for us scientists, is enough really ever enough? Just like the fact that we have perfectly working electronic devices that go from our wrists to our walls, but we’re still craving for better, for more, or sometimes, just different?


Rachana Acharya's wish may come true very soon: Flexible newspapers could hit the stands very soon. Photo: iStock.com/jcrosemann

Rachana Acharya’s wish may finally come true: Flexible newspapers and books could hit the stands very soon. Photo: iStock.com/jcrosemann

All major electronic devices and circuits work based on materials called inorganic semiconductors, the most widely used one being silicon. The way these materials are built is a lattice of atoms all put together in an arrangement that is continuous, periodic and ordered. (With minor faults here and there of course, nobody is perfect). Since the lattice is continuous, it means that the energy levels in individual atoms now line up to form continuous states, or bands through which electrons can move very easily and conduct charge. These electrons are only stopped or slowed down when they encounter aforementioned lattice imperfections. Basically, the lattice of Silicon would be like a running track with a few hurdles, but electrons are moving pretty fast in their particular track.

On the other hand, organic electronic materials, broadly classified into polymers and small molecules, don’t arrange themselves into periodic lattices. They form films where individual molecules are arranged in a more or less ordered fashion, where the more or less is decided by the way you process them. Along with this, the bonding in these molecules is a weaker Van der Waals bonding, which isn’t as strong as covalently bonded silicon. Although there isn’t any long range order, the molecular orbitals (or paths of the electrons moving in individual atoms) overlap intermittently, forming sites for the electrons to hop to and fro. Generally speaking, the behavior of electrons in these organic materials would be like rock climbing, where the electrons keep looking for points to travel forward.


Flexible substrates will introduce a whole new world of technological applications. Photo: meharris (CC BY-SA 3.0)

Flexible substrates will introduce a whole new world of technological applications. Photo: meharris (CC BY-SA 3.0)

The biggest advantage with organic electronics is their relatively lower processing and deposition temperatures, as these materials are often used close to room temperature. This opens up the opportunity to develop electronic devices, like transistors, solar cells, or LEDs on all kinds of plastic, flexible substrates, and even paper! (Believe me; people are really working on that). The materials are either solution-processed or thermally deposited in vacuum, and devices are patterned by a wide variety of techniques like lithography, masks, and microprinting. In the particular case of thin film transistors, low power complementary circuits have been fabricated and tested successfully. The major challenge faced by researchers today is to improve their performance to match already existing requirements. As an example, the mobility of electrons through thin film transistors, an indication of how fast they move is currently 2-3 orders of magnitude lower than silicon devices. The possible degradation of these materials overtime on exposure to air also remains a major concern. Nevertheless, instead of trying to replace silicon in traditional electronic appliances, these organic materials are really carving out their own niche in applications like intelligent labelling with RFID tags, large display sensor arrays, or portable devices.

My own research emphasizes on thin film transistors, particularly the gate dielectric component in the transistor. The gate dielectric layer separates the gate electrode from the semiconductor channel, so that when a bias is applied on the gate electrode, it induces an accumulation of charge carriers near the semiconductor-gate dielectric interface. These charge carriers then form the semiconducting channel and carry current through the transistor when a separate drain-source voltage is applied. The focus of my research is a hybrid gate dielectric layer, consisting of an inorganic metal oxide (e.g. Aluminum) and an organic self-assembled monolayer. What I intend to investigate is the effect of the gate dielectric layer, and its various aspects like the thickness, surface roughness on the properties of the transistor. Once I understand these effects, I also aim to achieve an optimum gate dielectric layer, which yields the most favorable transistor operating parameters, like threshold voltage and charge carrier mobility.

A few references for further reading:

  1. Embracing the Organics World, Nature Materials (Page 591, Vol 12, July 2013)
  2. A bright future for organic field effect transistors, Nature Materials (Vol. 5, Aug 2006)
  3. Low Power, High Impact Nature Materials, (Vol 6. March 2007)
  4. U. Zschiechang, Organic Electronics 25 (2015) 340–344

Interparticle Potentials and Supernovae: Windows for Physics beyond the Standard Model?

One of the greatest advances in the last century was the understanding that all phenomena in Nature – regardless of their scale – are ruled by four fundamental forces, namely, electromagnetism, weak and strong nuclear forces, and gravitation. A unifying theoretical scheme, the so-called Standard Model (SM), managed to bring the first three forces together, while gravity still resists being incorporated. The SM is a very successful construction and its predictions are in good agreement with experiment, but it still has some problems, and physicists love problems!

Some of the issues not covered by the SM are, for example, the non-zero masses for neutrinos which cause them to oscillate, or the fact that a large amount of the mass and energy in the Universe are actually not known (they were dubbed dark matter and energy). These and other puzzles have led physicists to build alternative theories supplementing the SM, whereby new forces and particles are introduced in the hope of healing some of the known maladies. Even though these beyond the Standard Model (BSM) scenarios usually require very high energies, they may have tangible consequences in our low-energy world. That is where my work in phenomenology starts.

The first part of my PhD was conducted in Rio de Janeiro, Brazil, at the Brazilian Centre for Research in Physics (CBPF), where we studied new forms of interactions between well-known sources, like electrons. In some BSM scenarios new interactions, carried by novel particles, may give rise to modifications in the already known ones, such as electromagnetism or even gravity. Our idea was to try to understand how new BSM forces would be felt, or measured, in case they coupled to low-energetic electrons in various ways while preserving highly desirable symmetry properties.

We have found that, indeed, it is possible to find traces of such novel interactions, specially between (spin-)polarized sources [1]. It would be therefore possible to study the mutual interaction of polarized matter and determine whether the observed behavior matches the expected one based on the SM – this could help putting upper limits on the specific parameters of BSM models. Another interesting consequence would be on the atomic level, where spectral lines, i.e., energy levels, could be shifted.

In a subsequent study we also worked on the energy between sources, but this time we did not focus on the mediating particles, but on the sources themselves: instead of dealing with spin-1/2 sources, like electrons, we treated sources with spin-1 in the low-energy limit. The difference in spin tells us that the two kinds of particles would respond differently to electromagnetic fields, for example. We found that the way these sources interact is not as different as one could have supposed, so that a wide range of similarities could be drawn [2]. This could help better understand the so-called hyper-nuclei, whose excitations may be in spin-1/2 or spin-1 states.

Already in Germany for my Cotutelle period at the University of Heidelberg, we changed the focus to a more phenomenological approach, but still dealing with BSM physics. We turned to the study of axion-like particles, or ALPs for short: hypothetical particles that interact very weakly with the photon, the mediator of the electromagnetic force. Because of this interaction, ALPs might leave tracks in many circumstances, from sub-atomic scales to cosmological ones. In particular, a very interesting possibility is to investigate the impact of ALPs in supernovae.


An illustration of a supernova. Photo: iStock.com/Pitris

An illustration of a supernova. Photo: iStock.com/Pitris

A supernova is a huge explosion at the final stage of the life of a massive star which releases enormous amounts of energy, possibly shining brighter than an entire galaxy. These extreme events are preceded by equally extreme conditions inside the progenitor star: ultra-high densities and temperatures, whereby matter – electrons, neutrons and protons – get crunched together to form a plasma. In this very hot medium ALPs may be produced and, since they interact only very weakly, scape the interior of the exploding star. After exiting the influence of the supernova the ALPs would fly a certain distance – statistically regulated by its mass and coupling to the photons – and then decay in two very energetic photons, usually in the gamma-ray region.  

We would then expect that, as soon as a supernova is observed, an extra amount of ALP-originated radiation would be detected, right? Yes, but unfortunately, for the famous case of SN 1987A – the most notable event of this kind since 1600 – no excess of gamma-rays could be found. This “null” result is actually very useful, as it serves to impose limits on the physical properties of ALPs, therefore helping to exclude values incompatible with observations. Our work focused on very massive ALPs in the context of SN 1987A as well as Betelgeuse, a red supergiant which is expected to go supernova in the next thousand years [3].

Besides my aforementioned PhD themes, I am currently interested in learning more about Lorentz violation and its phenomenological consequences. Lorentz symmetry is a corner stone of the theory of relativity and is a fundamental pillar of the SM. Possible deviations from it could have very interesting effects, such as variations in the speed of light or even induce changes in properties of elementary particles, such as the magnetic or electric dipole moment of the electron. This is a vast research field and learning more on this subject is being a very interesting challenge [4,5].



[1] F.A. Gomes Ferreira, P.C. Malta, L.P.R. Ospedal, J.A. Helayël-Neto, Topologically massive spin-1 particles and spin-dependent potentials, Eur. Phys. J. C 75, 5 238 (2015). Arxiv: hep-th/1411.3991.

[2] P.C. Malta, L.P.R. Ospedal, K. Veiga, J.A. Helayël-Neto, Comparative aspects of spin-dependent interaction potentials for spin-1/2 and spin-1 matter fields, Adv. High Energy Phys., 2531436 (2016). Arxiv: hep-ph/1510.03291.

[3] J. Jaeckel, P.C. Malta, J. Redondo, New limits on heavy ALPs: an analysis of SN 1987A, again, in preparation for publication.

[4] Y.M.P. Gomes, P.C. Malta, Lab-based limits on the Carroll-Field-Jackiw Lorentz-violating electrodynamics, submitted to Phys. Rev. D. Arxiv: hep-ph/1604.01102v3.

[5] G.P. de Brito, J.T. Guaitolini Jr, D. Kroff, P.C. Malta, C. Marques, Lorentz violation in simple QED processes. Arxiv: hep-ph/1605.08059v1.

Your Road to #LiNo16

The 2015 Lindau Nobel season has just ended but we are already looking forward to the 66th Lindau Nobel Laureate Meeting in 2016 dedicated to physics.

Are you a young scientist? Are you studying/doing research in physics? Have you ever dreamt about meeting the luminaries of science? Are you interested in meeting peers from around the world who are just as enthusiastic as you? Ever wanted to visit Germany’s beautiful southern region at the shores of Lake Constance? If you kept nodding while reading all of these questions then good for you – you’ve come to the right place! With this guide we want to answer all your questions and show you the way to become part of #LiNo16.


Step One

Each and every year the Lindau Nobel Laureate Meetings together with their academic partner institutions aim to bring the world’s brightest young minds in research together with the most revered scientists in their respective fields, the Nobel Laureates. To ensure sustaining the high level of excellency the Lindau Meetings are known for, we have compiled a list of selection criteria. If you are thinking about applying, please follow this link and take a close look at the prerequisites. Only if you meet all the requirements will your application have a chance to be successful.


Step Two

Check the list of our Academic Partner Institutions to find out if it contains a partner in your country. The Lindau Nobel Laureate Meetings are cooperating primarily with one partner institution per country. Therefore, if there is an institution listed for your country the only way to apply for participation is through them. Exception: Since we are based in Germany it is the only country where we have several partner institutions. If you’re applying from Germany read through the list to see which institution might be the right one to cover your field.

Case A – Your home country is represented on the list: Hurry to contact the listed institution to find out who is handling the Lindau nominations and talk to that person. She or he will guide you through the application process and will explain any special additional requirements the academic partner might have. If you’re interested, there is no time to lose – nominations are only possible until the 2 November 2015. Our academic partners will review all the applicants and then make their own decisions about who they want to nominate for the Lindau Meeting. The nominees of all our partners will then be sent to the scientific chairpersons of the Council for the Lindau Nobel Laureate Meetings who in turn will decide who will be eventually accepted.

Case B – Your home country is not represented on the academic partner list: First of all, don’t worry! The Lindau Nobel Laureate Meetings place great value in fostering the scientific dialogue not only between generations but also between cultures. We are proud to invite young scientists from over 80 countries and all corners of the world every year. To reach this goal we are always looking to find new academic partners in countries we don’t cover yet. For people from these places (or ex-pats who are not eligible for application through our partners) we have implemented the open application process. For the 66th Lindau Nobel Laureate Meeting the open application will be open from 21 September to 22 October, 2015. Applicants will have to register and fill out a short profile. The open applications will be directly reviewed by Lindau’s scientific chairpersons. If your application is accepted, it will be added to the pool of nominations by our academic partners giving you the same chances to participate as people whose applications come in through institutions. But remember: Open applicants must meet the same requirements as all the others.

To access the open application for the 66th Lindau Nobel Laureate Meeting please follow this link.


Special notes to current Academic Partners and possible future ones:

We produced this short film to stress how important the collaboration with academic partner institutions is for us. From providing the funding for the students’ participation in the Lindau Meetings to establishing high quality nomination processes all across the world that help to select the best of the best out of the thousands of applications – our meetings wouldn’t be possible without the help and support of our academic partners.

If you are reading this and working for a research organization, educational foundation or a similar entity in a country which is not part of our network yet, please don’t hesitate to contact us. We are always eager to find new partners among the world’s leading scientific organizations and to become even more globally connected. In general we are looking for academic partners that can represent and cover the entire country.

Of course there are also a lot of benefits for institutions partnering with the Lindau Nobel Laureate Meetings. Academic partners will be prominently featured in all of our communications efforts reaching the top media outlets from around the globe. Furthermore the international scientific network we created is invaluable in creating long-lasting relationships across borders, cultures and continents. But above all, the most important reason for becoming an academic partner is the opportunity to give the young scientists of your country the possibility to take part in the Lindau experience providing them with inspiration and motivation that last a lifetime.


4 of 650 young scientists that took part in this year's 65th Lindau Nobel Laureate Meeting. Photo: Ch. Flemming/Lindau Nobel Laureate Meetings.

4 of 650 young scientists that took part in this year’s 65th Lindau Nobel Laureate Meeting. Photo: Ch. Flemming/Lindau Nobel Laureate Meetings.


To all the Lindau alumni reading this:

Did you enjoy your stay in Lindau? Are you still in contact with the wonderful people you met here? Does it still help to motivate you in your research? If the answer to any one of those questions is ‘Yes!’ then why not help the next generation to secure their own Lindau experience? Become an ambassador for the Lindau Nobel Laureate Meetings and spread the word about us (and this blog post) to the people at your university. Try to answer their questions if you can or direct them to the people you know who can help them. As you know, we are also very active on social media. Don’t be shy about linking to our Facebook page and encouraging people to follow us on Twitter and use 2016’s newly born hashtag #LiNo16!


For all questions related to applying for the Lindau Nobel Laureate Meetings as young scientists or for any inquiries about academic partnerships please contact our young scientists support team.


I hope this blog post was helpful to anyone interested in applying for the 66th Lindau Nobel Laureate Meeting. We are already forward to getting to know you guys!

See you in Lindau!