MIOMD-XI Speakers    
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1.  Prof. Jean-Pierre Leburton, University of Illinois at Urbana-Champaign, USA
Late-Breaking Results: Soft THz Parametric Resonance for Hot Carriers in Graphene
Speaker Biography: Dr. Jean-Pierre Leburton is the G. Stillman Professor of Electrical and Computer Engineering at the University of Illinois in Urbana-Champaign. He is also Professor of Physics and a full time Research Faculty in the Beckman Institute. Dr. Leburton joined the University of Illinois in 1981 from Germany where he worked as a research scientist with the Siemens A.G. Research Laboratory in Munich. In 1992, he held the Hitachi LTD Chair on Quantum Materials at the University of Tokyo, and was a Visiting Professor in the Federal Polytechnic Institute in Lausanne, Switzerland in 2000. He is involved with research in nanostructures modeling and in quantum device simulation. His present research interest encompasses non-linear transport in quantum wires and carbon nanotubes, and molecular and ionic transport through semiconductor nanopores for biomolecule manipulation and sensing.

Summary: We investigate the onset of current oscillations induced by hot carriers interacting with high-energy optic phonons ℏω_op in graphene during the transient regime once the electric field is turned-on at room temperature. We show that the oscillations only take place for a specific range of constant electric fields within a voltage and sample length window, and is the direct consequence of the interplay between the electric force and the randomizing nature of deformation potential optic phonons in the linear band structure of graphene. Within this range of parameters the effect is predicted to manifest in damped terahertz oscillations of the carrier drift velocity and average energy. When an oscillating (AC) electric field is superimposed to a DC field F, the current oscillations are modified by the presence of the AC field, and its amplitude exhibits a soft resonance at the about half of the natural oscillation frequency ω_F=eFv_f/ℏω_op of the carriers in the presence of the DC field. This type of behavior is however different from normal parametric resonance that would occur at 2ω_F. In addition the resonance is rather soft with a Q-factor ≳1, as the system is strongly dissipative. Another interesting feature is the dephasing between current and AC field that shows a minimum as a function of the AC field frequency at low damping that softens to become monotonic at high damping for all AC field strengths. Applications for THz sources and detectors will be discussed.
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