Fluctuation-Induced Phenomena

Warum klebt ein Gecko an der Wand?' - Marty Oelschläger beim #64 Science Slam Berlin

As we go down in size not all things scale in proportion. Phenomena which are irrelevant at the macroscopic level become crucial within the micrometer or nanometer range. A large class of these effects are commonly known as noise- or fluctuation-induced phenomena and lead to the appearance of forces acting on the constituents of the system as well as to modifications of the system's dynamics. The origin of these effects is deeply rooted in quantum theory and in statistical mechanics. In the quantum case, they have their cornerstone in the famous uncertainty principle.

Fluctuation-induced phenomena play an important role in several fields of physics, ranging from electromagnetism to gravity, from statistical physics to cosmology, including multidisciplinary topics such as biophysics and optomechanics. They are relevant for the dynamics of black holes and for investigating the existence of extra dimensions, but they also govern biological processes and are important for colloidal matter, cell membranes and proteins. In the constant race towards miniaturization the understanding and the control of these interactions is essential for opening new avenues for fundamental investigations and for designing new and better performing devices.

Specifically, we pursue an intensive theoretical and computational investigation of the role of equilibrium and non-equilibrium fluctuations-induced interactions in simple and complex physical systems, providing new understanding and designs of novel interesting setups.

Marie Skłodowska-Curie CIG Project

INPhAS​ -- Fluctuation-Induced Interactions at the Interface between Photons, Atoms and Solids 


The INPhAS project targets an intensive theoretical and computational study of equilibrium and non-equilibrium fluctuation-induced interactions. It aims to acquire and enhance the competences in order to affront topics and problematics that are at the root of the future scientific development in all disciplines that deal with nanotechnologies. The methodology adopted will allow to put into evidence special and otherwise hidden features. The increased understanding will also facilitate the genesis of new ideas and the transportability of the results to other frameworks. This project is based on a multidisciplinary approach, combining concepts from different fields of physics, such as equilibrium and non-equilibrium physics, plasmonics, near field radiative heat transfer, diffusive electrodynamics, atomic physics and engineered materials. All these topics are intimately related within the framework of fluctuation-induced interactions, allowing for a complete perspec​tive and physical understanding of these phenomena.


Prof. Kurt Busch is the head of the Theoretical Optics & Photonics (TO&P) group at the Institute of Physics of the Humboldt University of Berlin where he is a full professor (W3). In addition, he is the leader of an independent research group at the Max Born Institute for Nonlinear Optics and Short-Pulse Spectroscopy in Berlin. His research interests are centered on the theoretical description of light propagation and light-matter interaction in complex photonic systems. This includes the theory of periodic photonic nano-structures, nano-plasmonic systems and few-photon transport problems.

Dr. Francesco Intravaia joined Theoretical Optics & Photonics group as a scientific staff member at the  Max Born Institute for Nonlinear Optics and Short-Pulse Spectroscopy in Berlin. Dr. Intravaia's experience spans a broad range of different but complementary arguments. These include decoherence of open quantum systems with few degrees of freedom, plasmonics, atomic physics, and nonequilibrium physics. All topics dovetail within the framework of this project, providing him with a unique set of skills and expertise. ​​


Dr. Philip T. Kristensen is working on a numerical implementation of a module for the numerical calculations of Casimir interaction in the home-made discontinuous Galerking time domain (DGTD) code developed by the Theoretical Optics & Photonics group.

M.Sc. Daniel Reiche j​oined the TO&P group in April 2015 as a Master student. He defended his master thesis "Equilibrium and non-equilibrium atom-surface interaction and the influence of spatial dispersion" in October 2016. In April 2017 he became PhD student and is working on the role of material, geometrical and statistical properties in equilibrium and nonequilibrium fluctuation-induced interactions.

M.Sc. Marty Oelschläger joined the TO&P group in June 2016 as a PhD student and he is working on the theory of fluctuation-induced phenomena in nano-photonic systems.

Christoph H. Egerland is a Bachelor student at the Humboldt University of Berlin and in April 2017 he joined the TO&P to work on his Bachelor thesis on the Casimir effect in graphene systems.

Former collaborators

Dr. Julia F. M. Werra wrote her PhD thesis within the TO&P group. She defended her work on "Probing plasmonic nanostructures: A theoretical study of light-matter interaction in graphene-based and metallic systems" in October 2016 and collaborated with the main scientists on the topic of fluctuation-induced interactions involving graphene and metallic systems.

News and updates
June 2017
  • The Theoretical Optics & Photonics group has been honered in "double dose". Julia and Daniel were both awarded with the Lise-Meitner-Preis ​for their PhD and Master thesis. Congratulations to both!!! The award cerimony is at 4 pm on July 21st in the Christian-Gerthsen lecture hall at the Institute of physics of the Humbodlt University.
April 2017
  • The summer semester 2017 officially started on April 18. Francesco and Marty are holding the lecture and the exercises on Fluctuation-induced Phenomena for the fourth time.


  • Daniel's paper on Spatial dispersion in atom-surface quantum friction has been accepted for publication in Physical Review B. Congratulations Daniel!​

    Synopsis. The paper discusses in detail  the influence of spatial dispersion on atom-surface quantum friction and shows that for atom-surface separations shorter than the carrier's mean free path within the material, the frictional force can be several orders of magnitude larger than that predicted by local optics. In addition, when taking into account spatial dispersion effects, it shows that the commonly used local thermal equilibrium approximation underestimates by approximately 95% the drag force. Unlike the treatment based on local optics, spatial dispersion in conjunction with corrections to local thermal equilibrium not only change the magnitude but also the distance scaling of quantum friction.

  • Christoph Egerland has officially started his Bachelor thesis on Casimir interactions in graphene systems. Welcome Christoph!

  • Daniel Reiche is now a PhD student of the TO&P group. He will work on the role of material, geometrical and statistics properties in equilibrium  and nonequilibrium fluctuation-induced interactions. Welcome back Daniel!
March 2017
  • The project INPhAS came to his end. In these three years of work the project led to advancement beyond the state of the art in the field of fluctuation-induced interactions. It produced a total of 10 publications in peer-review journals, 7 invited talks, 5 contributed talks and several highlights in scientific outlets. We thank our collaborators for this success!
February 2017







December 2016
  • The second funding period of the INPhAS project was characterized by a relevant outcome on the validity of the local thermal equilibrium approximation in fluctuation-induced interactions. Despite this approximation has been widely used to describe several nonequilibrium systems, it drastically fails in quantum friction. This major result was reported by several scientific outlets and the highlight “Quantum friction - beyond the local equilibrium approximation” appeared  on phys.org.



November 2016
  • Francesco gave this moth two invited taks:
  1. Role of material properties in equilibrium and non-equilibrium atom-surface interactions. Optikseminar, Universität Rostock, Rostock, Germany. 
  2. Equilibrium and Non-Equilibrium Fluctuation-Induced Interactions in multipartite systems. Colloquium of the Collaborative Research Center 925 “Light induced dynamics and control of correlated quantum systems”, Universität Hamburg, Hamburg, Germany.
October 2016
  • ​The paper "Non-Markovianity in atom-surface dispersion forces" has been published on Physical Review A.

    Synopsis. The paper discusses the failure of the Markov approximation in the description of atom-surface fluctuation-induced interactions, both in equilibrium (Casimir-Polder forces) and out of equilibrium (quantum friction). Using general theoretical arguments, it is shown that the Markov approximation can lead to erroneous predictions of such phenomena with regard to both strength and functional dependencies on system parameters. In particular, the behavior of the long-time power-law tails of two-time dipole correlations and their corresponding low-frequency behavior, neglected in the Markovian limit, affect the prediction of the force. These findings highlight the importance of non-Markovian effects in dispersion interactions.
September 2016
  • The paper "Failure of Local Thermal Equilibrium in Quantum Friction" has been published on Physical Review Letters.

    Synopsis. Recent progress in manipulating atomic and condensed matter systems has instigated a surge of interest in nonequilibrium physics, including many-body dynamics of trapped ultracold atoms and ions, near-field radiative heat transfer, and quantum friction. Under most circumstances the complexity of such nonequilibrium systems requires a number of approximations to make theoretical descriptions tractable. In particular, it is often assumed that spatially separated components of a system thermalize with their immediate surroundings, although the global state of the system is out of equilibrium. This powerful assumption reduces the complexity of nonequilibrium systems to the local application of well-founded equilibrium concepts. While this technique appears to be consistent for the description of some phenomena, we show that it fails for quantum friction by underestimating by approximately 80% the magnitude of the drag force. Our results show that the correlations among the components of driven, but steady-state, quantum systems invalidate the assumption of local thermal equilibrium, calling for a critical reexamination of this approach for describing the physics of nonequilibrium systems.
June 2016
  • Marty Oelschläger is now a PhD student of the TO&P group. He will work on the theory of fluctuation-induced phenomena at nano-photonic systems. Welcome Marty!
May 2016
  • Prof. Ulf Leonhardt from the Weizmann Institute of Science is guest of the TO&P group. In his colloquium on "Cosmology in the laboratory" he discussed several topics related to the INPhAS project.



April 2016
  • ​Francesco gave a talk at the workshop "Casimir and van der Waals physics: Progress and prospects" hosted in the IAS Building at The Hong Kong University of Science and Technology. The workshop's program focuses on recent developments in the fields of Casimir and van der Waals interactions and the prospects of novel applications of these forces. Francesco's presentation on the "Statistical Aspects of Quantum Friction" was recorded and the video appeared on Youtube.




December 2015
  • Daniel was awarded with a fellowship in the framework of PROMOS program funded by the DAAD. Congratulations! ​

The fellowship will allow him to spend two months at the Los Alamos National Laboratory, New Mexico, USA. There he will collaborate with Diego Dalvit on the topic of his Master thesis.

November 2015
  • Francesco is among the organizers of the Early Stage Researchers workshop on Nanoscale Quantum Optics. The workshop takes place in La Villette (Malta) on November 15-18 and it is funded by the EU COST Action MP1403. The aim of the workshop is 1) to provide a unique platform for the youngest researchers to familiarize themselves with their colleagues and form long-lasting networks; 2) to allow these researchers the opportunity to formally present their work to an audience of their peers; 3) to help PhD students close to graduation and older ESRs with information about the various (european and other) funding and employment options that are available to them.
June 2015



November 2014



March 2014
  • The project INPhAS started officially this month. In the next three years of work the project will try to advance the state of the art in the field of fluctuation-induced interactions.