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TT: Fachverband Tiefe Temperaturen

TT 24: Quantum-Critical Phenomena

TT 24.8: Vortrag

Dienstag, 19. März 2024, 11:30–11:45, H 2053

Manipulating topology of quantum phase transitions by flavor enhancement — •Gabriel Rein^1,2, Marcin Raczkowski¹, Toshihiro Sato^2,3, Zhenjiu Wang⁴, and Fakher F. Assaad^1,2 — ¹Institut für Theoretische Physik und Astrophysik Universität Würzburg, 97074 Würzburg, Germany — ²Würzburg-Dresden Cluster of Excellence ct.qmat, Universität Würzburg, 97074 Würzburg, Germany — ³Theoretical Solid State Physics, IFW Dresden, 01069 Dresden, Germany — ⁴Ludwig-Maximilians-Universität München, Theresienstr. 37, 80333 München, Germany

We consider a dynamically generated quantum spin Hall (QSH) state, characterized by skyrmion excitations of the SO(3) order parameter carrying charge 2e. A model described in [1] uses parameter λ to drive a continuous transition, akin to deconfined quantum criticality, from a QSH insulator to an s-wave superconductor (SSC) via the condensation of charge 2e skyrmions. Here we enhance the symmetry of the model by introducing an additional flavor index N_f=2. Remarkably, we observe a new Kékulé (VBS) phase and transitions between QSH/SSC as well as VBS/SSC. All phase transitions turn out to be of Ginzburg-Landau type. For the VBS/SSC transition we argue that this is due to a θ-term at θ=N_f π . For the QSH/SSC transition, we conjecture that in 2+1 d the non-linear sigma model with level N_f Wess-Zumino-Witten term has relevant operators that induce ordered phases, thus requiring fine-tuning for observing a continuous transition. Similarities to the 1+1 d case [2] are highlighted.

[1] Y. Liu et al., Nat. Comm. 10 (2019) 2658

[2] I. Affleck et al., Phys. Rev. B 36 (1987) 5291

Keywords: Topology; Theory; Wess-Zumino-Witten; Quantum phase transitions; Superconductivity