Dynamical spectral weight in YBa$_2$Cu$_3$O$_y$ probed by x-ray absorption spectroscopy

TL;DR

This study uses temperature-dependent x-ray absorption spectroscopy to reveal a dynamical spectral weight in YBa₂Cu₃O₇₋ₓ, linking pseudogap phenomena to high-energy bands and hole dynamics.

Contribution

It introduces the concept of a dynamical spectral weight in YBCO and demonstrates its relation to the pseudogap and hole dynamics, providing new insights into high-temperature superconductivity mechanisms.

Findings

Spectral weight changes significantly with temperature in underdoped YBCO.

The dynamical spectral weight α is linearly proportional to the pseudogap temperature.

α decreases as doping approaches the undoped limit.

Abstract

The comprehensive study of the temperature dependent x-ray absorption spectroscopy (XAS) reveals a dynamical spectral weight $\alpha$ in YBa$_2$Cu$_3$O$_y$ (YBCO). Large spectral weight changes for both the Upper Hubbard band and the Zhang-Rice band due to dynamics of holes are experimentally found in the underdoped regime. A large value of $\alpha \geq 0.3$ is indispensable to describing XAS of YBCO with the conservation of states. The value of $\alpha$ is linearly proportional to the pseudogap temperature in the underdoped regime, but becomes smaller as the doping level goes to the undoped limit. Our results clearly indicate that the pseudogap is related to the double occupancy and originates from bands in higher energies.