Novel anisotropy in the superconducting gap structure of Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} probed by quasiparticle heat transport

TL;DR

This study uncovers an unusual anisotropic superconducting gap structure in Bi-2212, revealing complex pairing interactions through quasiparticle heat transport measurements that challenge the simple d-wave symmetry model.

Contribution

It provides the first evidence of directional anisotropy in the quasiparticle populations and gap structure in Bi-2212 using heat transport, indicating more complex pairing interactions.

Findings

Quasiparticle populations differ between nodal directions

Anisotropic heat transport reveals complex gap structure

Plateau in thermal conductivity observed only along b-axis

Abstract

Since the nature of pairing interactions is manifested in the superconducting gap symmetry, the exact gap structure, particularly any deviation from the simple d_{x^2-y^2} symmetry, would help elucidating the pairing mechanism in high-T_c cuprates. Anisotropic heat transport measurement in Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} (Bi-2212) reveals that the quasiparticle populations are different for the two nodal directions and thus the gap structure must be uniquely anisotropic, suggesting that pairing is governed by interactions with a rather complicated anisotropy. Intriguingly, it is found that the "plateau" in the magnetic-field dependence of the thermal conductivity is observed only in the b-axis transport.