# Mesoscopic quantum effects in a bad metal, hydrogen-doped vanadium dioxide

## TL;DR

This paper reports mesoscopic quantum effects such as weak localization magnetoresistance and conductance fluctuations in hydrogen-doped VO2, a poor metal, challenging existing theories that assume good metallicity for analyzing quantum corrections.

## Contribution

It demonstrates the presence of quantum interference effects in a bad metal, expanding understanding of mesoscopic phenomena beyond conventional good metals.

## Key findings

- Observation of weak localization magnetoresistance in H$_{x}$VO$_{2}$
- Detection of conductance fluctuations in hydrogen-doped VO$_{2}$
- Challenges in analyzing quantum effects in poor metals

## Abstract

The standard treatment of quantum corrections to semiclassical electronic conduction assumes that charge carriers propagate many wavelengths between scattering events, and succeeds in explaining multiple phenomena (weak localization magnetoresistance (WLMR), universal conductance fluctuations, Aharonov-Bohm oscillations) observed in polycrystalline metals and doped semiconductors in various dimensionalities. We report apparent WLMR and conductance fluctuations in H$_{x}$VO$_{2}$, a poor metal (in violation of the Mott-Ioffe-Regel limit) stabilized by the suppression of the VO$_{2}$ metal-insulator transition through atomic hydrogen doping. Epitaxial thin films, single-crystal nanobeams, and nanosheets show similar phenomenology, though the details of the apparent WLMR seem to depend on the combined effects of the strain environment and presumed doping level. Self-consistent quantitative analysis of the WLMR is challenging given this and the high resistivity of the material, since the quantitative expressions for WLMR are derived assuming good metallicity. These observations raise the issue of how to assess and analyze mesoscopic quantum effects in poor metals.