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

摘要

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