Vortex and Surface Phase Transitions in Superconducting Higher-order Topological Insulators
Year: 2020
Type: article
Abstract: Topological insulators, having intrinsic or proximity-coupled s-wave superconductivity, host Majorana zero modes (MZMs) at the ends of vortex lines. The MZMs survive up to a critical doping of the TI at which there is a vortex phase transition that eliminates the MZMs. In this work, we show that the phenomenology in higher-order topological insulators (HOTIs) can be qualitatively distinct. In particular, we find two distinct features. (i) We find that vortices placed on the gapped (side) surfaces of the HOTI, exhibit a pair of phase transitions as a function of doping. The first transition is a surface phase transition after which MZMs appear. The second transition is the well-known vortex phase transition. We find that the surface transition appears because of the competition between the superconducting gap and the local T-breaking gap on the surface. (ii) We present numerical evidence that shows strong variation of the critical doping for the vortex phase transition as the center of the vortex is moved toward or away from the hinges of the sample. We believe our work provides new phenomenology that can help identify HOTIs, as well as illustrating a promising platform for the realization of MZMs.
Source: Physical Review Letters
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: MRSEC: Illinois Materials Research Center, G2786210319, Programs on Critical Problems in Physics, Astrophysics and Biophysics at the Aspen Center for Physics, CAREER: Interplay of topology and geometry in materials with strong spin-orbit coupling, Kavli Institute for Theoretical Physics, CAREER: Two-dimensional Van Der Waals systems with tunable spin-orbit coupling
OpenAlex ID: W2976349120