Ulf Gennser

CNRS Laboratoire de Photonique et de Nanostructures

Abstract:

Technical progress often opens up the possibility for novel experiments. Two such developments in our group, a hybrid system consisting of a micron-sized metallic island with a near-perfect electron transmission to a GaAs/AlGaAs 2-dimensional electron gas, and cryogenic amplifiers with ultra-low noise, have enabled us to investigate mesoscopic phenomena previously unexplored.

Firstly, we have managed to measure the quantum limit of heat conduction through a single electric channel. The demonstrated agreement with the theoretically predicted value establishes experimentally this basic building block of quantum thermal transport. The achieved accuracy of below 10% opens access to many experiments involving the quantum manipulation of heat.[1]

Secondly, our metal island, working as an implementation of a single electron transistor, can be tuned to have to degenerate macroscopic charge states, which effectively work as pseudo-spins. We have been able to use it to demonstrate a ‘charge’ Kondo effect. In contrast to other Kondo nanostructures, each conduction channel connecting the island to an electrode constitutes a distinct and fully tunable Kondo channel, thereby providing an unprecedented access to the tantalizing multi-channel Kondo physics.[2]

[1] S. Jezouin et al., “Quantum Limit of Heat Flow Across a Single Electronic Channel,” Science 342, 601 (2013).[2] Z. Iftikhar et al., “Two-channel Kondo effect and renormalization with macroscopic quantum charge states,” to be published in Nature (2015).

Biography:

Ulf Gennser received his Ph.D. in 1992 from Columbia University (New York), working on resonant tunneling in SiGe heterostructures. He is currently the group leader of « Physics and Technology of Nanostructures » at the Laboratoire de Photonique et de Nanostructures, CNRS, France, and is responsible for the molecular beam epitaxy of high mobility electronic systems. His main interest is in mesoscopic physics, and currently, among other topics, he is involved in phase coherence studies, energy transfer and heat transport in the quantum Hall effect regime, as well as studies of the laws of electricity in the presence of quantum coherence.

For more information, contact Prof. Subramanian Iyer (ssiyer77@g.ucla.edu)

Date/Time:
Date(s) - Sep 21, 2015
1:00 pm - 3:00 pm

Location:
EE-IV Shannon Room #54-134
420 Westwood Plaza - 5th Flr., Los Angeles CA 90095