AI 中文总结
本研究以笼目超导体CsV$_3$Sb$_5$为对象，明确无场超导二极管效应的对称性要求，揭示其随机畴控制特性，发现超导态时间反演对称性破缺与电荷密度波序相关。
AI 中文摘要
无场超导二极管效应需要同时存在破缺空间反演对称性和内部时间反演对称性（TRS）的场，因此是探测超导体中隐藏序的敏感工具。在中心对称的笼目结构AV$_3$Sb$_5$中，反演对称性通常会阻碍超导二极管效应的观测。此外，尽管已有研究报道CsV$_3$Sb$_5$的超导态中存在TRS破缺，但该破缺是由超导性本身产生还是继承自电荷密度波（CDW）序，目前尚未明确。本研究表明， pristine CsV$_3$Sb$_5$器件无本征无场超导二极管效应，而表面氧化或不对称刻蚀可激活显著的非互易超流；该响应具有随机性，极性和大小随扫描过程变化，表明存在亚稳态的TRS破缺畴构型。小的面外磁场可稳定超导二极管响应，与这类畴的场选择效应一致；最后，当Ti掺杂抑制长程CDW序时，超导二极管效应（SDE）消失。本研究明确了CsV$_3$Sb$_5$中无场SDE的对称性要求，揭示其随机的畴控制特性，并将超导态TRS破缺与CDW相关序关联起来。
英文摘要
Field-free superconducting diode effects require both inversion-symmetry breaking and an internal time-reversal-symmetry (TRS) breaking field, making them sensitive probes of hidden order in superconductors. In centrosymmetric kagome AV$_3$Sb$_5$, the inversion symmetry generally should generally preclude the observation of the superconducting diode effect. Furthermore, though TRS breaking has been reported in the superconducting regime of CsV$_3$Sb$_5$, whether it is generated by superconductivity or inherited from charge-density-wave (CDW) order remains unresolved. Here we show that pristine CsV$_3$Sb$_5$ devices exhibit no intrinsic field-free superconducting diode effect, whereas surface oxidation or asymmetric etching activates a large nonreciprocal supercurrent. Moreover, the response is stochastic, with sweep-dependent polarity and magnitude, indicating metastable TRS-breaking domain configurations. Small out-of-plane magnetic fields stabilize the superconducting diode response, consistent with field selection of such domains. Finally, when long-range CDW order is suppressed by Ti doping, the SDE disappears. Our results establish the symmetry requirements for the field-free SDE in CsV$_3$Sb$_5$, reveal its stochastic domain-controlled character, and link superconducting-state TRS breaking to CDW-related order.
Comments33 pages,18 figures
