Superconductivity from the condensation of topological defects in a quantum spin-Hall insulator

• Published in: Nature communications Vol. 10; no. 1; pp. 2658 - 6
• Main Authors: Liu, Yuhai, Wang, Zhenjiu, Sato, Toshihiro, Hohenadler, Martin, Wang, Chong, Guo, Wenan, Assaad, Fakher F.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 14.06.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 639/705/1042; 639/766/119/2792/4128; 639/766/530/2795; Band theory; Broken symmetry; Computer simulation; Condensed matter physics; Critical point; Defects; Fermions; Field theory; Humanities and Social Sciences; Insulators; multidisciplinary; Phase transitions; Physics; Science; Science (multidisciplinary); Simulation; Spin-orbit interactions; Superconductivity; Symmetry; Topology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-10372-0

The discovery of quantum spin-Hall (QSH) insulators has brought topology to the forefront of condensed matter physics. While a QSH state from spin-orbit coupling can be fully understood in terms of band theory, fascinating many-body effects are expected if it instead results from spontaneous symmetry breaking. Here, we introduce a model of interacting Dirac fermions where a QSH state is dynamically generated. Our tuning parameter further allows us to destabilize the QSH state in favour of a superconducting state through proliferation of charge-2e topological defects. This route to superconductivity put forward by Grover and Senthil is an instance of a deconfined quantum critical point (DQCP). Our model offers the possibility to study DQCPs without a second length scale associated with the reduced symmetry between field theory and lattice realization and, by construction, is amenable to large-scale fermion quantum Monte Carlo simulations. Deconfined quantum critical points separate two phases with different broken symmetries, which puts them beyond the standard Landau theory of phase transitions. Here the authors present a model with a monopole-free deconfined quantum critical point, making it more amenable to detailed numerical studies.