The Center for Excitonics Seminar Series

Leonid Levitov

Department of Physics, Massachusetts Institute of Technology

Materials in which heat and entropy can be transmitted by directed ballistic pulses, are of keen interest and importance both scientifically and technologically. Scientifically, they enable fundamentally new unconventional modes of energy transfer which rely on collective wave-like behavior akin to light or sound propagation. Technologically, directed ballistic heat pulses can trigger new approaches to energy transduction in solids. Collective wave-like energy transfer has been predicted for relativistic matter under extreme conditions (cosmic sound). This talk will discuss an electronic analog of cosmic sound that can be realized in the thermal electron-hole plasma in graphene. The new behavior originates from rapid exchange of energy and momentum in particle collisions leading to energy propagation as a collective weakly damped oscillation. Due to the electronic nature of this mode, the estimated propagation velocity can be orders of magnitude faster than that for previously studied phonon mechanisms. The energy mode is uncharged at charge neutrality, but becomes coupled to charge dynamics upon doping. This coupling, combined with the techniques developed recently to study plasmons in nanosystems such as carbon nanotubes and graphene, can be employed for an all-electric excitation and detection of energy transport.

This talk will also briefly discuss several other topics of interest concerning plasmons, hot carriers and excitons in atomically thin layered materials: multiple carrier generation in the photo-excitation cascade, plasmon generation in the presence of a DC current (electronic flute), exciton Berry’s phase, topological currents and anomalous Hall transport.


Leonid Levitov received his M.A. in Physics cum laude at Moscow Physical-Technical Institute in 1985 and his Ph.D. in Theoretical Physics at Landau Institute in 1989. He pioneered in the theory of quasicrystals, orderly materials with non-crystallographic symmetries, discovered in 1985  and in the theory of quantum noise in coherent electron transport.   He also developed theory of electronic properties of graphene, in particular,  new device concepts based on common-path interference and Klein tunneling, and theory of spin Hall effect which explained the giant nonlocality observed in graphene.  He has published over a 100 refereed papers and reviews in the fields of quantum transport, solid-state quantum computing, cold atoms, quantum noise, growth and pattern formation.  Currently, he is a Professor of Physics at MIT and leads the Condensed Matter Theory Research Group.

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RLE Center for Excitonics