Revealing Majorana Zero Modes in Vortex Cores via Nonmagnetic Impurities

TL;DR

This paper shows that nonmagnetic impurities can help detect Majorana zero modes in superconductors by creating a clear energy gap, making them easier to identify for quantum computing.

Contribution

The paper reveals that nonmagnetic impurities enhance the energy gap for Majorana zero modes, challenging the need for large Δ/EF ratios.

Findings

Nonmagnetic impurities increase the energy gap between Majorana zero modes and other states.

Majorana zero modes remain unaffected by impurity-induced potentials, leading to a clear zero-bias peak.

Engineered pinning centers in s-wave superconductors offer a practical way to detect Majorana zero modes.

Abstract

Majorana zero modes (MZMs) localized in vortex cores of topological superconductors are widely regarded promising building blocks for fault-tolerant quantum computation. However, their unambiguous detection is hindered by the extremely small energy spacing separating them from conventional Caroli-de Gennes-Matricon states. Using a microscopic Bogoliubov-de Gennes approach, we demonstrate that nonmagnetic impurities, rather than suppressing, can substantially enhance the energy gap between MZMs and other vortex core excitations. The robustness of MZMs against local perturbations ensures that while conventional states are shifted by impurity-induced potentials, the MZMs remain intact. This results in a pronounced zero-bias peak in the local density of states. Our results dispute the widespread assumption that large Δ/EF values—where Δ is the superconducting gap and EF is the Fermi energy—are required to detect MZMs, and instead indicate that purposefully engineered pinning centers in conventional s-wave superconductors offer a practical and experimentally accessible alternative.

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