Optical and thermodynamic properties of the high-temperature superconductor HgBa_2CuO_4+delta

TL;DR

This study investigates the optical and thermodynamic properties of the high-temperature superconductor HgBa_2CuO_4+delta, revealing insights into superfluid density, spectral weight changes, and the nature of the superconducting transition.

Contribution

It provides new experimental data on HgBa_2CuO_4+delta's optical spectra and specific heat, and links these to superconductivity mechanisms and energy changes.

Findings

Superfluid density follows the rho_s = sigma_dc T_c scaling relation.

Optical spectral weight increases, indicating a kinetic energy change of ~0.5 meV/Cu.

The specific heat anomaly is significantly smaller than in YBCO and Bi-2212, suggesting thermal fluctuation dominance.

Abstract

In- and out-of-plane optical spectra and specific heat measurements for the single layer cuprate superconductor Hg-1201 at optimal doping (Tc = 97 K) are presented. Both the in-plane and out-of-plane superfluid density agree well with a recently proposed scaling relation rho_{s}=sigma_{dc}T_{c}. It is shown that there is a superconductivity induced increase of the in-plane low frequency spectral weight which follows the trend found in underdoped and optimally doped Bi-2212 and optimally doped Bi-2223. We observe an increase of optical spectral weight which corresponds to a change in kinetic energy of approximately 0.5 meV/Cu which is more than enough to explain the condensation energy. The specific heat anomaly is 10 times smaller than in YBCO and 3 times smaller than in Bi-2212. The shape of the anomaly is similar to the one observed in YBCO showing that the superconducting transition is governed by thermal fluctuations.