# Regensburg 2019 – wissenschaftliches Programm

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# TT: Fachverband Tiefe Temperaturen

## TT 60: Quantum-Critical Phenomena (joint session TT/DY)

### TT 60.1: Vortrag

### Donnerstag, 4. April 2019, 15:00–15:15, H23

**Superconductivity from the Condensation of Topological Defects in a Quantum Spin-Hall Insulator** — Yuhai Liu^{1}, Zhenjiu Wang^{2}, Toshihiro Sato^{2}, Martin Hohenadler^{2}, Chong Wang^{3}, Wenan Guo^{1}, and •Fakher F. Assaad^{2} — ^{1}Department of Physics, Beijing Normal University, Beijing 100875, China — ^{2}Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany — ^{3}Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada N2L 2Y5

The discovery that spin-orbit coupling can generate a new state of matter in the form of quantum spin-Hall (QSH) insulators has brought topology to the forefront of condensed matter physics. While QSH states from spin-orbit coupling can be fully understood in terms of band theory, fascinating many-body effects are expected if the state instead results from interaction-generated symmetry breaking. In particular, topological defects of the corresponding order parameter provide a route to exotic quantum phase transitions. Here, we introduce a model in which the condensation of skyrmion defects in an interaction-generated QSH insulator produces a superconducting (SC) phase. Because vortex excitations of the latter carry a spin-1/2 degree of freedom numbers, the SC order may be understood as emerging from a gapless spin liquid normal state. The QSH-SC transition is an example of a deconfined quantum critical point (DQCP), for which we provide an improved model with only a single length scale that is accessible to large-scale quantum Monte Carlo simulations.