Topological surface states in dense solid hydrogen

TL;DR

This paper demonstrates that dense solid hydrogen at high pressures can host topological surface states characteristic of line-node semimetals, offering explanations for experimental anomalies and predicting surface superconductivity.

Contribution

It identifies topological semimetal phases in dense hydrogen, revealing surface states and potential superconductivity, expanding understanding of high-pressure elemental phases.

Findings

Dense hydrogen phases can be line-node topological semimetals.

Surface states are present, affecting electronic properties.

Potential for surface superconductivity in high-pressure hydrogen.

Abstract

It has recently been established that two-dimensional massless graphene-like systems and three-dimensional line-node topological semimetals comprise a special class of centrosymmetric materials where edge/surface states of topological nature inevitably appear in some k-regions. We show that the phases of solid hydrogen produced at megabar pressures can be line-node topological semimetals. In such phases, the material exhibits topological surface states and therefore can be a poor bulk metal but good surface conductor. The results may help to explain discrepant high-pressure experimental data reported for dense hydrogen as well as provide predictions for future measurements, including possible surface superconductivity in hydrogen. Related topological behavior may be expected in high-pressure phases formed in other elements including simple metals.