What is measured when measuring a thermoelectric coefficient?

2023

Colloquium

Title

What is measured when measuring a thermoelectric coefficient?

Time

2023年11月1日（星期三）

15:00-16:00

Venue

     理科楼5号楼300号报告厅

01.

摘要

Abstract

A thermal gradient generates an electric field in any solid hosting mobile electrons. In the presence of a [real or a fictious] magnetic field, this electric field has a transverse component. These are known as Seebeck and Nernst coefficients. As Callen argued decades ago, the Seebeck effect quantifies the entropy carried by a flow of charged particles in the absence of thermal gradient, and we now begin to understand the Nernst conductivity as a measure of the entropy carried by a flow of magnetic flux in absence of thermal gradient.I will review experiments on a variety of solids, ranging from semi-metals to superconductors, from correlated metals to topological magnets, indicating that the rough amplitude of the thermoelectric response is set by fundamental units and material-dependent length scales. Specifically, the Nernst conductivity scales with the square of the mean-free-path in metals. It acquires an anomalous component in magnets scaling with the square of the fictitious magnetic length. Finally, ephemeral Cooper pairs, present in the normal state of a superconductor, generate a Nernst signal scaling with the square of the superconducting coherence length.

02.

个人简介

Speaker's biography   

Kamran Behnia

           ESPCI&CNRS

Paris Science et Lettres University

Kamran Behnia is based at Ecole Supérieure de Physique et de Chimie Industrielles (ESPCI) in Paris. His research focuses on collective quantum phenomena in a variety of solids ranging from semimetals to superconductors. His book “Fundamentals of Thermoelectricity” was published by Oxford University Press in 2015 and is a well-recognized modern textbook on thermoelectricity, balancing both theoretical description and experimental surveys. He became a fellow of American Physical Society in 2012 and a recipient (2021) of Prix Jaffé, awarded by the French Academy of Sciences. He has been a Divisional Associate Editor (DAE) of Physical Review Letters and a member of the Board of Reviewing Editors (BoRE) of Science since 2013.

图文编辑：刘真

责任编辑：叶丹、朱敏