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arXiv 2103.01244cond-mat.supr-concond-mat.mes-hall
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作为手征超导特征的无序感应电流

Disorder-induced currents as signatures of chiral superconductivity

Madhuparna Karmakar, R. Ganesh

摘要:

手征超导体被期望沿着样品边缘携带自发的、手征的和永久的电流。然而,尽管有几种候选材料可用,但在实验中尚未观察到这种电流。在这篇文章中,我们提出了一种替代探针的形式杂质诱导的手性电流。我们首先证明,一个单一的非磁性杂质诱导一个环绕手征电流。它的方向依赖于序参量的手征性和杂质势的符号。基于这一观察,我们考虑多种杂质的情况,例如,实现为沉积在候选手性超导体的表面上的吸附原子。我们对比两种情况下获得的响应:(a)当杂质的符号都相同时,以及(b)当杂质的正负符号混合时。前者导致样品内的相干电流,由单个电流回路的融合产生。后者会产生随机手征的回路,导致不相干的局部电流。这两种情况可以通过测量感应磁场使用最新的探头,如钻石NV中心区分。我们认为,杂质感应电流可能比边缘电流更容易观察,因为它们可以通过改变杂质强度和浓度来调节。我们使用正方形晶格上的$p_x \pm i p_y$超导性的玩具模型来证明这些结果。我们开发了一种改进的Bogoliubov deGennes(BdG)模拟方案,其中的序参量以及磁场确定自洽。

英文摘要:

Chiral superconductors are expected to carry a spontaneous, chiral and perpetual current along the sample edge. However, despite the availability of several candidate materials, such a current has not been observed in experiments. In this article, we suggest an alternative probe in the form of impurity-induced chiral currents. We first demonstrate that a single non-magnetic impurity induces an encircling chiral current. Its direction depends on the chirality of the order parameter and the sign of the impurity potential. Building on this observation, we consider the case of multiple impurities, e.g., realized as adatoms deposited on the surface of a candidate chiral superconductor. We contrast the response that is obtained in two cases: (a) when the impurities are all identical in sign and (b) when the impurities have mixed positive and negative signs. The former leads to coherent currents within the sample, arising from the fusion of individual current loops. The latter produces loops of random chirality that lead to incoherent local currents. These two scenarios can be distinguished by measuring the induced magnetic field using recent probes such as diamond NV centres. We argue that impurity-induced currents may be easier to observe than edge currents, as they can be tuned by varying impurity strength and concentration. We demonstrate these results using a toy model for $p_x \pm i p_y$ superconductivity on a square lattice. We develop an improved scheme for Bogoliubov deGennes (BdG) simulations where both the order parameter as well as the magnetic field are determined self-consistently.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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