令和 4年度（２０２２年度）第1回 物理教室談話会

Title	Systematic characterization of crystal electric field effects and spin-phonon hybridization in CsYbSe2
Speaker	Prof. Minhyea Lee (U. Colorado Boulder)
Date	July 1, 2022 (Fri) 15 : 00 ～
Place	Room 307 (Collaboration Room), 3rd Floor, Collaboration Centre
abstract	Insulating quantum magnets occupy a special position in condensed matter physics. Because of their freedom from the strong decoherence affecting charged systems, they are at the forefront of fundamental research into quantum matter, providing candidate systems for realizing novel ground states and exotic magnetic and topological excitations. For the same reason, they are also playing an increasingly crucial technological role in areas including spintronics and quantum information processing. 　Magnetic rare-earth ions go beyond the straightforward paradigm of geometrical frustration in Heisenberg antiferromagnets by introducing competing energy scales, and in particular their strong spin-orbit coupling creates multiple split crystal electric-field levels, leading to anisotropic effective spin models with intrinsic frustration. 　In this talk, I will present our recent analysis of the high-field magnetotropic response of CsYbSe 2 , providing an unambiguous determination of the crystal-electric-field parameters as well as leading order exchange interactions in CsYbSe2 . In addition, we propose a novel and highly generic model to explain the field dependence of thermal conductivity of CsYbSe 2 , where phonon heat conduction can acquire unique nontrivial field-dependence through the hybridization of acoustic phonons and spin flip excitations of the ground doublet, via strain-modulation of the magnetic g- tensor. This, in turn, advances our understanding of spin-phonon interaction in thermal transport, and will enrich our experimental tools for recognizing new spin states. Leaflet
Contact	Division of Superconducting and Functional Materials Kaya KOBAYASHI (ex. 8631)