Anisotropic and tunable vortex topology in multiband iron-based superconductors

TL;DR

This paper reveals anisotropic vortex topologies in multiband iron-based superconductors, identifying a unique x-vortex that supports Majorana vortices and can be controlled via strain, opening new avenues for quantum device applications.

Contribution

It introduces a novel anisotropic vortex topology in multiband FeSCs, highlighting the unique x-vortex with dual topological phases and potential for quantum technology.

Findings

x-vortex supports unpaired Majorana vortices over a wide parameter range

Uniaxial strain can modulate x-vortex phases and Majorana vortex stability

Distinct topological phase diagrams for z-vortex and x-vortex

Abstract

Building on the multiband nature of iron-based superconductors (FeSCs), we have uncovered pronounced anisotropy in Majorana vortex topology arising from the interaction between vortex orientation and multiple electronic topologies. This anisotropy manifests in two distinct vortex configurations: the z-vortex and x-vortex, oriented perpendicular and parallel to the Dirac axis (z-axis for FeSCs), respectively. The x-vortex exhibits a unique duality, displaying two distinct topological phase diagrams. One is strikingly simple, comprising only trivial and topological superconducting phases, and remains resilient to multiband entanglement. The other mirrors the z-vortex's complex diagram, featuring alternating trivial, topological crystalline and topological superconducting phases. Crucially, the former is exclusive to the x-vortex and supports unpaired Majorana vortices across a wide parameter range, even with Dirac nodes in electronic bands. Notably, uniaxial strain can modulate these x-vortex phases, enabling the x-vortex to support both stable Majorana vortices and rich exotic physics in a controllable manner. Moreover, we propose that the x-vortex offers promising advantages for developing iron-based superconducting quantum devices. Our findings introduce a novel paradigm in vortex topology within multiband superconducting systems, highlighting the x-vortex as a promising platform for exploring Majorana physics and advancing iron-based superconducting quantum technology.