T$_d$-MoTe$_2$薄膜中的超导二极管效应与大的磁手性各向异性
Superconducting Diode Effect and Large Magnetochiral Anisotropy in T$_d$-MoTe$_2$ Thin Film
AI总结：
本文研究了无序非中心对称超导体T$_d$-MoTe$_2$薄膜中的非互易效应，在弱面外磁场下观测到近20%二极管效率及大磁手性各向异性，并通过唯象理论揭示了自旋轨道耦合不对称结构对非互易输运的影响。
摘要：
在时间反演不变性缺失的情况下，缺乏空间反演对称性的金属可能表现出非互易电荷输运——这是一种磁手性各向异性，表现为相反电流方向下的电阻不相等。如果同时发生超导，电荷传输可能在一个方向上变得无耗散，而在相反方向上仍保持耗散，从而实现超导二极管。通过直流和交流测量，我们研究了具有无序的非中心对称超导体T$_d$-MoTe\textsubscript{2}薄膜中的非互易效应。我们观察到在毫特斯拉量级的弱面外磁场下，非互易超导临界电流的二极管效率接近20\\%，且磁手性各向异性系数高达$\SI{5.9e8}{\per\tesla\per\ampere}$。面外磁场下整流效率的极大增强可能归因于涡旋棘轮效应，这种效应自然出现在具有无序的非中心对称超导体中。有趣的是，与Rashba系统中的发现不同，最强的面内非互易效应并非出现在磁场垂直于电流方向时。我们发展了一个唯象理论，证明这种奇特行为可归因于T$_d$-MoTe\textsubscript{2}中自旋轨道耦合的不对称结构。我们的研究突出了晶体学对称性如何关键地影响非互易输运，并将进一步推动设计具有最佳性能的超导二极管的研究。
英文摘要：
In the absence of time-reversal invariance, metals without inversion symmetry may exhibit nonreciprocal charge transport -- a magnetochiral anisotropy that manifests as unequal electrical resistance for opposite current flow directions. If superconductivity also sets in, the charge transmission may become dissipationless in one direction while remaining dissipative in the opposite, thereby realizing a superconducting diode. Through both direct-current and alternating-current measurements, we study the nonreciprocal effects in thin films of the noncentrosymmetric superconductor T$_d$-MoTe\textsubscript{2} with disorders. We observe nonreciprocal superconducting critical currents with a diode efficiency close to 20\%~, and a large magnetochiral anisotropy coefficient up to $\SI{5.9e8}{\per\tesla\per\ampere}$, under weak out-of-plane magnetic field in the millitesla range. The great enhancement of rectification efficiency under out-of-plane magnetic field is likely abscribed to the vortex ratchet effect, which naturally appears in the noncentrosymmetric superconductor with disorders. Intriguingly, unlike the finding in Rashba systems, the strongest in-plane nonreciprocal effect does not occur when the field is perpendicular to the current flow direction. We develop a phenomenological theory to demonstrate that this peculiar behavior can be attributed to the asymmetric structure of spin-orbit coupling in T$_d$-MoTe\textsubscript{2}. Our study highlights how the crystallographic symmetry critically impacts the nonreciprocal transport, and would further advance the research for designing the superconducting diode with the best performance.
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