Imaging nanoscale Fermi surface variations in an inhomogeneous superconductor

TL;DR

This paper introduces a novel microscopy technique to visualize nanoscale variations in the Fermi surface of inhomogeneous cuprate superconductors, revealing local doping differences that influence their electronic properties.

Contribution

It demonstrates the first direct imaging of spatially varying Fermi surfaces in a superconductor, advancing understanding of nanoscale inhomogeneity in these materials.

Findings

Fermi surface varies on nanometer scales in cuprates

Local doping fluctuations correlate with Fermi surface changes

Method enables new insights into inhomogeneous electronic states

Abstract

Particle-wave duality suggests we think of electrons as waves stretched across a sample, with wavevector k proportional to their momentum. Their arrangement in "k-space," and in particular the shape of the Fermi surface, where the highest energy electrons of the system reside, determine many material properties. Here we use a novel extension of Fourier transform scanning tunneling microscopy to probe the Fermi surface of the strongly inhomogeneous Bi-based cuprate superconductors. Surprisingly, we find that rather than being globally defined, the Fermi surface changes on nanometer length scales. Just as shifting tide lines expose variations of water height, changing Fermi surfaces indicate strong local doping variations. This discovery, unprecedented in any material, paves the way for an understanding of other inhomogeneous characteristics of the cuprates, like the pseudogap magnitude, and highlights a new approach to the study of nanoscale inhomogeneity in general.