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O: Fachverband Oberflächenphysik
O 61: Focus Session: Frontiers of Electronic-Structure Theory V (joint session O/HL)
O 61.1: Talk
Wednesday, March 29, 2023, 15:00–15:15, TRE Ma
Phase transitions in the two-dimensional Su-Schrieffer-Heeger model — •Changan Li1, Songbo Zhang2, Sangjun Choi1, Jan Budich3, and Björn Trauzettel1 — 1Institute for theoretical physics and astrophysics, University of Würzburg, Wuerzburg, Germany — 2Department of Physics, University of Zürich, Winterthurerstrasse 190 8057, Zürich, Switzerland — 3Institute of Theoretical Physics, Technische Universität Dresden, 01062 Dresden, Germany
The 2D Su-Schrieffer-Heeger (SSH) model is endowed with rich topological physics. First we show that the random flux can induce a metal-band insulator transition in the 2D SSH, thus reporting the first example of such a transition. Remarkably, we find that the resulting insulating phase can even be a higher-order topological insulator with zero-energy corner modes and fractional corner charges. Employing both level statistics and finite-size scaling analysis, we characterize the metal-band insulator transition and numerically extract its critical exponent. By proposing another inclined 2D SSH model, a deformed one, we show that a pair of Dirac points protected by space-time inversion symmetry appear in the semimetallic phase. Interestingly, the locations of these Dirac points are not pinned to any high-symmetry points of the Brillouin zone but highly tunable through parameter modulations. Moreover, the merging of two Dirac points undergoes a topological phase transition, which leads to either an anisotropic topological insulating phase or a nodal-line metallic phase.