SciPost Physics

SciPost Phys. 12, 196 (2022) · published 14 June 2022

• doi: 10.21468/SciPostPhys.12.6.196
• pdf
• BiBTeX
• RIS
• Submissions/Reports
• 

Abstract

We study the edge physics of the deconfined quantum phase transition (DQCP) between a spontaneous quantum spin Hall (QSH) insulator and a spin-singlet superconductor (SC). Although the bulk of this transition is in the same universality class as the paradigmatic deconfined Neel to valence-bond-solid transition, the boundary physics has a richer structure due to proximity to a quantum spin Hall state. We use the parton trick to write down an effective field theory for the QSH-SC transition in the presence of a boundary. We calculate various edge properties in an $N\to\infty$ limit. We show that the boundary Luttinger liquid in the QSH state survives at the phase transition, but only as "fractional" degrees of freedom that carry charge but not spin. The physical fermion remains gapless on the edge at the critical point, with a universal jump in the fermion scaling dimension as the system approaches the transition from the QSH side. The critical point could be viewed as a gapless analogue of the quantum spin Hall state but with the full $SU(2)$ spin rotation symmetry, which cannot be realized if the bulk is gapped.

• Moharramipour et al., Solvable models for 2+1D quantum critical points: Loop soups of 1+1D conformal field theories
  SciPost Phys. 16, 061 (2024) [Crossref]
• Xu et al., Deconfined quantum critical point with nonlocality
  Phys. Rev. B 106, 155131 (2022) [Crossref]
• Lee et al., Quantum Criticality Under Decoherence or Weak Measurement
  PRX Quantum 4, 030317 (2023) [Crossref]
• Wen et al., Bulk-boundary correspondence for intrinsically gapless symmetry-protected topological phases from group cohomology
  Phys. Rev. B 107, 245127 (2023) [Crossref]
• Ye et al., Topological characterization of Lieb-Schultz-Mattis constraints and applications to symmetry-enriched quantum criticality
  SciPost Phys. 13, 066 (2022) [Crossref]