# Strong Particle-Hole Symmetry Breaking in a 200 kelvin Superconductor

## TL;DR

This paper demonstrates that the high-temperature superconductor H$_3$S exhibits significant particle-hole symmetry breaking at low energies, deviating from traditional symmetric models due to its unique density of states structure.

## Contribution

It provides first-principles calculations revealing strong particle-hole symmetry breaking in H$_3$S, challenging conventional low-energy superconductor models.

## Key findings

- Strong PHS-breaking dynamics in H$_3$S due to density of states structure
- Deviation from textbook superconductor behavior at low energies
- Momentum-resolved spectral densities show asymmetry

## Abstract

The superconducting state of metals has long provided a classic example of particle-hole symmetry (PHS) at low energy. Fermionic self-energy results based on first principles theory for the electron-phonon coupling in H$_3$S presented here illustrate strong PHS-breaking dynamics arising from the underlying sharp structure in the fermionic density of states. Thus H$_3$S is not only the superconductor with the highest critical temperature $T_c$ (through 2018), but its low energy, low temperature properties deviate strongly from textbook behavior. The minor momentum and band dependence of the fermionic self-energy allows evaluation of the momentum-resolved and zone-averaged spectral densities and interacting thermal distribution function, all of which clearly illustrate strong particle-hole asymmetry.