The Pseudogap in La(2-x)Sr(x)CuO(4): A Raman Viewpoint

TL;DR

This study uses Raman scattering to investigate the pseudogap in La(2-x)Sr(x)CuO(4), revealing doping and temperature dependence, and linking the pseudogap to magnetic interactions with a characteristic energy scale.

Contribution

It provides a detailed Raman spectroscopy analysis of the pseudogap in La214, connecting spectral weight depletion and scattering rates to magnetic energy scales and doping levels.

Findings

Pseudogap causes low-energy spectral weight depletion near (pi, 0) and (0, pi).

Spectral weight shifts to higher energies associated with multi-magnon scattering.

Pseudogap energy scale Eg is approximately equal to the super-exchange energy J.

Abstract

We report the results of Raman scattering experiments on single crystals of La(2-x)Sr(x)CuO(4) [La214] as a function of temperature and doping. In underdoped compounds low-energy B1g spectral weight is depleted in association with the opening of a pseudogap on regions of the Fermi surface located near (pi, 0) and (0, pi). The magnitude of the depletion increases with decreasing doping, and in the most underdoped samples, with decreasing temperature. The spectral weight that is lost at low-energies (omega < 800 cm-1) is transferred to the higher energy region normally occupied by multi-magnon scattering. From the normal state B2g spectra we have determined the scattering rate Gamma(omega, T) of qausiparticles located near the diagonal directions in k-space, (pi/2, pi/2) regions. In underdoped compounds, Gamma(omega, T) is suppressed at low temperatures for energies less than Eg(x) ~ 800 cm-1. The observed doping dependence of the two-magnon scattering and the scattering rate suppression thus suggest that the pseudogap is characterized by an energy scale Eg ~ J, where J is the antiferromagnetic super-exchange energy. Comparison with the results from other techniques provides a consistent picture of the pseudogap in La214.