Particle-hole symmetry reveals failed superconductivity in the metallic phase of two-dimensional superconducting films

TL;DR

This study investigates the metallic phase in disordered two-dimensional superconductors, revealing that particle-hole symmetry persists in this phase, which challenges traditional understanding of superconductivity and localization.

Contribution

It demonstrates that the metallic state in 2D superconductors retains particle-hole symmetry, providing new insights into the nature of this unconventional phase.

Findings

Metallic phase exhibits saturated resistivity at zero temperature.

Vanishing Hall resistivity indicates preserved particle-hole symmetry.

Transition from superconductor to metal is tunable by magnetic field.

Abstract

Electrons confined to two dimensions display an unexpected diversity of behaviors as they are cooled to absolute zero. Noninteracting electrons are predicted to eventually "localize" into an insulating ground state, and it has long been supposed that electron correlations stabilize only one other phase: superconductivity. However, many two-dimensional (2D) superconducting materials have shown surprising evidence for metallic behavior, where the electrical resistivity saturates in the zero-temperature limit, the nature of this unexpected metallic state remains under intense scrutiny. We report electrical transport properties for two disordered 2D superconductors, indium oxide and tantalum nitride, and observe a magnetic field-tuned transition from a true superconductor to a metallic phase with saturated resistivity. This metallic phase is characterized by a vanishing Hall resistivity, suggesting that it retains particle-hole symmetry from the disrupted superconducting state.