Unconventional superconductivity from lattice quantum disorder

TL;DR

This paper reveals that incorporating nuclear quantum effects into lattice models uncovers a quantum disordered phase in superconductors, which is crucial for understanding and predicting high-temperature superconductivity.

Contribution

It introduces a first-principles approach that includes nuclear quantum effects, identifying a lattice quantum disordered phase linked to superconductivity.

Findings

Discovered a lattice quantum disordered phase in H3S and La3Ni2O7.

The phase boundary aligns with the superconducting Tc.

The maximum Tc occurs within this quantum disordered phase.

Abstract

Unconventional superconductivity presents a defining and enduring challenge in condensed matter physics. Prevailing theoretical frameworks have predominantly emphasized electronic degrees of freedom, largely neglecting the rich physics inherent in the lattice. Although conventional phonon theory offers an elegant description of structural phase diagrams and lattice dynamics, its omission of nuclear quantum many-body effects results in misleading phase diagram interpretations and, consequently, an unsound foundation for superconducting theory. Here, by incorporating nuclear quantum many-body effects within first-principles calculations, we discover a lattice quantum disordered phase in superconductors H3S and La3Ni2O7. This phase occupies a triangular region in the pressure-temperature phase diagram, whose left boundary aligns precisely with Tc of the left flank of the superconducting dome. The Tcmax of this quantum disordered phase coincides with the maximum of superconducting Tc, indicating this phase as both the origin of superconductivity on the dome's left flank and a key ingredient of its pairing mechanism. Our findings advance the understanding of high-temperature superconductivity and establish the lattice quantum disordered phase as a unifying framework, both for predicting new superconductors and for elucidating phenomena in a broader context of condensed matter physics.