Quantum Disordered Regime and Spin Gap in the Cuprate Superconductors

TL;DR

This paper explores the transition from quantum critical to disordered regimes in high-temperature cuprate superconductors, analyzing experimental data to understand spin excitation gaps and their relation to superconductivity.

Contribution

It presents a scenario linking spin gaps and correlation lengths, providing a unified explanation consistent with various experimental observations in cuprates.

Findings

Spin excitations develop a gap above T_c.

The spin gap increases as the correlation length decreases.

Experimental data are consistent with the proposed scenario.

Abstract

We discuss the crossover from the quantum critical, $z\!=\!1$, to the quantum disordered regime in high-T$_c$ materials in relation to the experimental data on the nuclear relaxation, bulk susceptibility, and inelastic neutron scattering. In our scenario, the spin excitations develop a gap $\Delta\!\sim\!1/\xi$ well above T$_c$, which is supplemented by the quasiparticle gap below T$_c$. The above experiments yield consistent estimates for the value of the spin gap, which increases as the correlation length decreases.