Itahashi Yuki M, Ideue Toshiya, Hoshino Shintaro, Goto Chihiro, Namiki Hiromasa, Sasagawa Takao, Iwasa Yoshihiro
Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan.
Department of Physics, Saitama University, Saitama, 338-8570, Japan.
Nat Commun. 2022 Mar 29;13(1):1659. doi: 10.1038/s41467-022-29314-4.
Nonreciprocal or even-order nonlinear responses in symmetry-broken systems are powerful probes of emergent properties in quantum materials, including superconductors, magnets, and topological materials. Recently, vortex matter has been recognized as a key ingredient of giant nonlinear responses in superconductors with broken inversion symmetry. However, nonlinear effects have been probed as excess voltage only under broken time-reversal symmetry. In this study, we report second harmonic transport under time-reversal symmetry in the noncentrosymmetric trigonal superconductor PbTaSe. The magnitude of anomalous nonlinear transport is two orders of magnitude larger than those in the normal state, and the directional dependence of nonlinear signals are fully consistent with crystal symmetry. The enhanced nonlinearity is semiquantitatively explained by the asymmetric Hall effect of vortex-antivortex string pairs in noncentrosymmetric systems. This study enriches the literature on nonlinear phenomena by elucidating quantum transport in noncentrosymmetric superconductors.
对称性破缺系统中的非互易或偶数阶非线性响应是探测量子材料（包括超导体、磁体和拓扑材料）中涌现特性的有力手段。最近，涡旋物质已被认为是具有破缺反演对称性的超导体中巨大非线性响应的关键要素。然而，非线性效应仅在时间反演对称性破缺的情况下作为过电压进行了探测。在本研究中，我们报道了非中心对称三角超导体PbTaSe在时间反演对称性下的二次谐波输运。反常非线性输运的幅度比正常态下大两个数量级，并且非线性信号的方向依赖性与晶体对称性完全一致。非中心对称系统中涡旋 - 反涡旋弦对的不对称霍尔效应半定量地解释了增强的非线性。这项研究通过阐明非中心对称超导体中的量子输运，丰富了关于非线性现象的文献。
