Bose-Einstein condensations of magnons in quantum magnets with spin-orbit coupling: a new type of dangerously irrelevant operators and exotic excitations
（Mississippi State university）
We study the response of a quantum magnet with spin-orbit coupling (SOC) to a Zeeman field and find novel classes of quantum phase transitions driven by the magnon condensations at commensurate (C-) or in-commensurate (IC-) momenta. We identify a new type of dangerously irrelevant operator which is irrelevant near the transition, does not change the symmetry breaking ground state, but changes its excitation spectrum to an exotic form.This is in sharp contrast to the known dangerously irrelevant operator.We name the new one Type-II dangerously irrelevant operator in contrast to the previously known one which we name Type-I.We derive the relations between the quantum spin and the order parameters of the effective actions which is crucial to determine the spin-orbital structures of all these quantum phases.The intrinsic differences between the magnon condensations at the C- and IC- momenta are explored.The experimental implications to cold atoms or materials with SOC are presented.
简介：叶锦武教授是美国耶鲁大学理论物理博士。他现在是美国密西西比州立大学教授.叶教授主要研究领域是强相互作用的电子, 玻色子, 自旋，光子等的合作现象和量子或拓扑相变理论,他的研究还涉及超对称性破缺，共形场论和各种量子或拓扑相的量子引力对偶.
His two most recent research directions are on
(1) Topological Phases,topological phase transitions driven by interactions in various spin-orbit coupled systems.
(2) Quantum chaos and quantum information scramblings in cavity QED systems or in Sachdev-Ye-Kitaev (SYK) models.Connections among SYK models, conformal field theory and topological phases.