Determination of the superconducting gap in near optimally doped Bi_2Sr_{2-x}La_xCuO_{6+\delta} (x ~ 0.4) from low-temperature specific heat

TL;DR

This study measures the low-temperature specific heat of near optimally doped Bi-2201 to confirm the d-wave symmetry of its superconducting gap and determine the gap magnitude, aligning with spectroscopic results.

Contribution

It provides bulk evidence for the d-wave pairing symmetry and quantifies the superconducting gap in Bi-2201 using specific heat measurements.

Findings

Identification of T^2 term and H dependence consistent with d-wave pairing

Determination of the superconducting gap magnitude (~12 meV)

Agreement with spectroscopic measurements

Abstract

Low-temperature specific heat of the monolayer high-Tc superconductor Bi_2Sr_{2-x}La_xCuO_{6+\delta} has been measured close to the optimal doping point (x ~ 0.4) in different magnetic fields. The identification of both a T^2 term in zero field and a \sqrt{H} dependence of the specific heat in fields is shown to follow the theoretical prediction for d-wave pairing, which enables us to extract the slope of the superconducting gap in the vicinity of the nodes (v_{\Delta}, which is proportional to the superconducting gap \Delta_0 at the antinodes according to the standard d_{x^2-y^2} gap function). The v_{\Delta} or \Delta_0 (~ 12 meV) determined from this bulk measurement shows close agreement with that obtained from spectroscopy or tunneling measurements, which confirms the simple d-wave form of the superconducting gap.