Distinct charge and spin gaps in underdoped YBa2Cu3O7-x

TL;DR

This study reveals two distinct, doping-dependent, temperature-independent gaps in underdoped YBa2Cu3O7-x, associated with charge and spin excitations, suggesting different underlying local states in the pseudogap regime.

Contribution

It provides a systematic comparison of charge and spin gaps, identifying their distinct nature and doping dependence in underdoped YBa2Cu3O7-x, advancing understanding of the pseudogap.

Findings

Charge and spin gaps are distinct and doping-dependent.

Both gaps are temperature-independent and exist above and below Tc.

Charge gap linked to pair-breaking local gap; spin gap linked to intra-gap triplet state.

Abstract

A systamatic quantitative comparison of ''pseudogap'' values obtained from the analysis of charge and spin excitation spectroscopies in underdoped YBa2Cu3O7-x using a temperature-independent gap shows two distinct excitations, one visible in spin-flip spectroscopies like NMR and spin polarized neutron scattering, and the other in charge excitation spectoscopies like single particle tunneling and time-resolved quasiparticle relaxation. Both appear to decrease with doping x approximately as 1/x and are T-independent, existing above and below Tc. We suggest that the charge excitation can be attributed to a pair-breaking local gap, while the spin excitation can be explained by an intra-gap local triplet state.