Direct visualization of quasiparticle concentration around superconducting vortices

TL;DR

This paper introduces a noninvasive, atomic-scale method to visualize and quantify quasiparticle concentration around superconducting vortices, aiding in the design of quantum circuits and understanding quasiparticle dynamics.

Contribution

It demonstrates a novel application of scanning tunneling noise microscopy to directly visualize quasiparticle distribution around vortices in superconductors.

Findings

Quasiparticle concentration increases as vortices get closer.

The method detects quasiparticles as small as 10^-4.

Quasiparticle behavior impacts vortex-based Majorana qubits.

Abstract

Bogoliubov quasiparticles play a crucial role in understanding the behavior of a superconductor, and in achieving reliable operations of superconducting quantum circuits. Diagnosis of quasiparticle poisoning at the nanoscale provides invaluable benefits in designing superconducting qubits. Here, we use scanning tunneling noise microscopy to locally quantify quasiparticles by measuring the effective charge. Using the vortex lattice as a model system, we directly visualize the spatial variation of the quasiparticle concentration around superconducting vortices, which can be described within the Ginzburg-Landau framework. This shows a direct, noninvasive approach for the atomic-scale detection of relative quasiparticle concentration as small as 10^-4 in various superconducting qubit systems. Our results alert of a quick increase in quasiparticle concentration with decreasing intervortex distance in vortex-based Majorana qubits.