Optical Spectroscopy as a Probe of Gaps and Kinetic Electronic Energy in p- and n-type cuprates

TL;DR

This study uses optical spectroscopy to analyze the electronic gaps and kinetic energy in p- and n-type cuprates, revealing doping-dependent spectral weight changes and pseudogap signatures.

Contribution

It provides a comprehensive optical spectral weight dataset across doping levels, highlighting differences in Fermi surface topology and pseudogap features in cuprates.

Findings

Fermi surface is closed in overdoped samples

Underdoped Pr2-xCexCuO4 shows Fermi arcs and pseudogap signatures

Differences in pseudogap visibility between Pr2-xCexCuO4 and Bi2Sr2CaCu2O8+δ

Abstract

The real part of the optical in-plane conductivity of p-- and n--type cuprates thin films at various doping levels was deduced from highly accurate reflectivity measurements. We present here a comprehensive set of optical spectral weight data as a function of the temperature $T (> T_c$), for underdoped and overdoped samples. The temperature dependence of the spectral weight is not universal. Using various cut-off frequencies for the spectral weight, we show that n--type Pr$_{2-x}$Ce$_x$CuO$_4$ and p--type Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ exhibit both similarities and striking differences. The Fermi surface is closed in overdoped metallic samples. In underdoped Pr$_{2-x}$Ce$_x$CuO$_4$ samples, it clearly breaks into arcs, giving rise to a "pseudogap" signature. It is argued that such a signature is subtle in underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$.