[Theory-seminars] Fwd: Physics Colloquium & Condensed Matter Seminar

[Mary Fox]

-------- Original Message --------
Subject: 	Physics Colloquium & Condensed Matter Seminar
Date: 	Mon, 27 Apr 2015 19:24:40 +0000
From: 	Wilkinson, Eleonor V <evwilk at wm.edu>
To: 	'physics0607 at physics.wm.edu' <physics0607 at physics.wm.edu>, 
'undergrads0607 at physics.wm.edu' <undergrads0607 at physics.wm.edu>



*_PHYSICS COLLOQUIUM_*

Friday, May 1, 2015

4:00 PM

Small Hall, Room 110

*Georg Schwiete *[Host: E. Rossi]

Johannes Gutenberg Universität Mainz

*Title of Talk:*

/Nuclear/Particle/Astrophysics with Slow Neutrons/

*Abstract:*

The influence of disorder on interacting many-body systems plays a 
prominent role in modern condensed matter physics. Not only is the 
presence of disorder often unavoidable in the complex materials used in 
experiment, disorder leads to fascinating phenomena in their own right. 
Generally speaking, disorder tends to slow down the motion of particles 
and even very weak disorder may be sufficient to completely localize 
them. The addition of interactions to the problem leads to a plethora of 
new phenomena. In this talk, I will discuss selected examples that 
illustrate the rich physics of interacting disordered systems at low 
temperatures: In experiment, one often observes that disordered films on 
the verge of becoming superconducting develop a pronounced resistance 
maximum. I will explain our theoretical understanding of this surprising 
effect. Next, I intend to discuss the expansion of a cloud of bosons 
subjected to a disorder potential. Despite the obvious difference 
between these systems, an efficient theoretical approach can in both 
cases be based on the analysis of effective diffusion equations. This 
description allows to clearly identify the physical mechanisms that are 
relevant at low temperatures. If time allows, I will also compare charge 
and heat transport in the disordered electron liquid using a similar 
language.

*//*

*/*Cookies & coffee will be served in Room 122 at 3:30 PM/*

********************

*_CONDENSED MATTER SEMINAR_*

Monday, May 4, 2015

3:30 PM

Small Hall, Room 122

*Georg Schwiete *[Host: E. Rossi]

Johannes Gutenberg Universität Mainz

*Title of Talk:*

/Transport of heat in the disordered Fermi and electron liquids/

*Abstract:*

The main subject of this talk is thermal transport in the disordered 
Fermi and electron liquids at low temperatures. I plan to start with a 
brief introduction to the physics of quantum corrections to conductivity 
in disordered systems and the phenomenology of the metal-insulator 
transition in two-dimensional electron systems. Then, I will contrast 
approaches to the calculation of electric and thermal transport. A 
principle difficulty for the description of thermal transport is that 
temperature is an internal parameter, and a temperature gradient does 
not correspond to an external “mechanical” force like a the one 
originating from an electric potential. We use Luttinger’s gravitational 
potentials as sources for finding the heat density and its correlation 
function. For a comprehensive study, we extend the RG analysis developed 
for electric transport by including the gravitational potentials into 
the RG scheme. The analysis reveals that for the disordered Fermi liquid 
the Wiedemann-Franz law remains valid even in the presence of quantum 
corrections caused by the interplay of diffusion modes and the 
electron-electron interaction. For the disordered electron liquid we 
additionally analyze inelastic processes induced by the Coulomb 
interaction at sub-temperature energies. While the general form of the 
correlation function has to be compatible with energy conservation, 
these inelastic processes are at the origin of logarithmic corrections 
violating the Wiedemann-Franz law.

*//*

References:

G. Schwiete and A. M. Finkel’stein, Renormalization group analysis of 
thermal transport in the disordered Fermi liquid, Phys. Rev. B 90, 
155441 (2014)

G. Schwiete and A. M. Finkel’stein, Thermal transport and the Wiedemann 
Franz law in the disordered Fermi liquid, Phys. Rev. B 90, 060201(R) (2014)

G. Schwiete and A. M. Finkel’stein, Keldysh approach to the 
renormalization group analysis of the disordered electron liquid, Phys. 
Rev. B 89, 075437 (2014)

******

*Eleonor V. Wilkinson*

Administrative & Office Specialist

The College of William & Mary-Physics
Small Hall, Room 123
300 Ukrop Way
Williamsburg, VA 23185

Telephone: 757-221-3503

Fax: 757-221-3540



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