Seminar: Experimental Problems of Anderson Localization - Many Body Aspects

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Seminar: Experimental Problems of Anderson Localization - Many Body Aspects

31 Oct 2019, 14:00 – 15:00

XLG2 Auditorium
UCL Department of Chemistry, 20 Gordon St
London
WC1H 0AJ
United Kingdom

We are pleased to announce a special seminar to be given by Prof Sir Michael Pepper primarily aimed for students and early career researchers towards the fascinating field of many-body localization which has recently gained enormous attention particularly its experimental realisation in semiconductor nanostructures.

Abstract: Since Anderson proposed the concept of localization by disorder its importance has become clear for many aspects of condensed matter physics including the Quantum Hall Effect, Quantum Computation as well as photonics. Subsequent work by Anderson, Abrahams, Thouless and many others established that quantum interference augments localization by disorder and explains many phenomena which were hitherto observed but not understood. It was established that disorder localizes all states in 1D, but 2D is marginal and in the absence of a magnetic field or spin- orbit coupling all states in 2D are localized, as in classical diffusion, but this is very difficult to observe. Concepts such as the mobility edge, variable range hopping and others were proposed by Mott and form the basis for understanding many metal-insulator transitions.

A particular question, much debated, was whether the electron-electron interaction could drive conductivity when disorder localized all states. This was answered in 2005 by Althshuler and colleagues who showed to all orders of perturbation theory that it could not in a closed quantum system. This situation, which has generated enormous interest, is termed “Many Body Localization” and is predicted to be characterised by a number of unique features such as zero conductance at a finite temperature and the breakdown of the Eigenstate Thermalisation Hypothesis leading to the localization of energy.

In this seminar the basic features of Anderson and Many Body forms of localization will be discussed and attention given to experimental issues which resulted from studies of Anderson localization and may be precursors to Many Body Localization.

Prof Sir Michael Pepper

Pender Professor of Nanoelectronics at UCL Department of Electronic and Electrical Engineering UCL

UCL

Prof Sir Michael Pepper, FRS, FREng is the Pender Professor of Nanoelectronics at Department of Electronic and Electrical Engineering, University College London and also affiliated with London Centre for Nanotechnology. As a post-doc he worked with Phil Anderson and Nevill Mott on localization and has long been at the forefront of experimental quantum condensed matter physics. He pioneered the study of quantum effects seen in low dimensional electron gas systems — where electrons behave as a gas but their flow is constrained to zero, one or two dimensions. His discoveries have led to the development of the field of semiconductor-based nanoelectronics.

He was first to confirm experimentally in detail the theory of Anderson transitions, where a material can be switched between metal- and insulator-like behaviour and was one of three authors of the first paper announcing the discovery of the quantum Hall effect. Some of the notable fundamental discoveries resulted from Sir Michael’s group are: experimental verification of Anderson localization, co-discovery of the Quantum Hall effect, technology for the development of one-dimensional channels, quantized conductance in one-dimensional channel, electrostatically defined quantum dots, charge detection using one-dimensional system, the 0.7 conductance anomaly, Wigner crystallization and detection in one-dimensional systems, quantized electron pumping at high frequency and the recently found non-magnetic fractional quantized conductance in holes and electrons.