Helical Topological Superconducting Pairing at Finite Excitation Energies

TL;DR

This paper predicts a new form of helical topological superconductivity at finite energies in multiband superconductors, featuring tunable Dirac surface states protected by symmetry, expanding the understanding of topological phases beyond the Fermi surface.

Contribution

It introduces a novel mechanism for topological superconductivity involving interband pairing and finite-energy surface states, with potential material realizations.

Findings

Finite-energy helical Dirac surface states emerge in proposed superconductors.

Surface states are tunable via chemical potential and band-splitting.

Protection of states relies on time-reversal and crystalline symmetries.

Abstract

We propose helical topological superconductivity away from the Fermi surface in three-dimensional time-reversal-symmetric odd-parity multiband superconductors. In these systems, pairing between electrons originating from different bands is responsible for the corresponding topological phase transition. Consequently, a pair of helical topological Dirac surface states emerges at finite excitation energies. These helical Dirac surface states are tunable in energy by chemical potential and strength of band-splitting. They are protected by time-reversal symmetry combined with crystalline two-fold rotation symmetry. We suggest concrete materials in which this phenomenon could be observed.