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Tuesday, June 11

Field-induced thermal transport in Bose-Einstein condensation antiferromagnets

Sasha Chernyshev, University of California, Irvine
Materials Science & Technology Division Seminar
11:00 AM — 12:00 PM, Building 4100, Room C-201
Contact: Brian Sales (salesbc@ornl.gov), 865.576.7646

Abstract

After a highly biased, but historical, introduction into thermal transport in insulating magnets, I shall attempt brief and not legally binding remarks on the theory of this phenomenon in a subclass of antiferromagnets referred to as the Bose-Einstein condensation (BEC) antiferromagnets. Terminology will be introduced and experiments will be explained.

Recent experiments in BEC quantum magnets exhibit a dramatic evolution of the thermal conductivity in magnetic field. We provide a detailed explanation of several unusual features of the data. We identify the leading impurity-scattering interaction and demonstrate that its renormalization explains the enigmatic absence of the asymmetry in the low-T thermal conductivity data, while such an asymmetry is prominent in many other physical quantities. The observed "migration" of the thermal conductivity peak away from the transition points vs. temperature is explained as due to a competition between an increase in the number of heat carriers and an enhancement of their mutual scattering. An important role of the three-boson scattering processes in these systems is also discussed.