主题：Topological multicriticality of spin-orbit-coupled electrons in one dimension
Henrik Johannesson is a professor in University of Gothenburg (Sweden), his research areas are theoretical physicals, condensed matter theory, and statistical physics. He published 47 papers from 2003 to 2019.
The theory of quantum phase transitions (QPTs) is one of the corner stones in the study of quantum matter. A central tenet is that a closing of the gap to the first excited level, accompanied by a nonanalyticity in the ground state energy in the thermodynamic limit, is a marker of a QPT. In this talk I will report on a finding that challenges this assertion. The phase diagram of a one-dimensional multiband insulator with spin-orbit-coupled electrons supports trivial and topological gapped phases separated by intersecting critical surfaces. The intersections define multicritical lines across which the gap closes and the ground state energy becomes nonanalytical but without a phase transition. I propose a simple picture for how multicriticality gives rise to this apparent anomaly.