Charge Friedel oscillations in a Mott insulator

TL;DR

This paper predicts that ghost Fermi surfaces in Mott insulators cause detectable Friedel-like oscillations in electron density near impurities, providing a potential method to observe these elusive features.

Contribution

It introduces a theoretical framework linking ghost Fermi surfaces to observable Friedel oscillations in Mott insulators, suggesting a new detection approach.

Findings

Ghost Fermi surfaces induce slowly decaying density oscillations.

Oscillation period encodes geometric information of the ghost Fermi surface.

Potential experimental signatures for detecting ghost Fermi surfaces.

Abstract

When a metal undergoes a transition to an insulator it will lose its electronic Fermi surface. Interestingly in some situations a `ghost' Fermi surface of electrically neutral spin carrying fermions may survive into the insulator. Such a novel ghost Fermi surface has been proposed to underlie the properties of a few different materials but its direct detection has proven elusive. In this paper we show that the ghost Fermi surface leads to slowly decaying spatial oscillations of the electron density near impurities or other defects. These and related oscillations stem from the sharpness of the ghost Fermi surface and are direct analogs of the familiar Friedel oscillations in metals. The oscillation period contains geometric information about the shape of the ghost Fermi surface which can be potentially exploited to detect its existence.