Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA.
Nat Commun. 2023 Apr 12;14(1):2055. doi: 10.1038/s41467-023-37210-8.
A growing number of two-dimensional superconductors are being discovered in the family of exfoliated van der Waals materials. Due to small sample volume, the superfluid response of these materials has not been characterized. Here, we use a local magnetic probe to directly measure this key property of the tunable, gate-induced superconducting state in MoS. We find that the backgate changes the transition temperature non-monotonically whereas the superfluid stiffness at low temperature and the normal state conductivity monotonically increase. In some devices, we find direct signatures in agreement with a Berezinskii-Kosterlitz-Thouless transition, whereas in others we find a broadened onset of the superfluid response. We show that the observed behavior is consistent with disorder playing an important role in determining the properties of superconducting MoS. Our work demonstrates that magnetic property measurements are within reach for superconducting devices based on exfoliated sheets and reveals that the superfluid response significantly deviates from simple BCS-like behavior.
越来越多的二维超导体在剥离范德华材料家族中被发现。由于样品体积小，这些材料的超流响应尚未得到表征。在这里，我们使用局部磁探针直接测量可调谐栅控超导态中 MoS 的这一关键性质。我们发现，背栅对转变温度的影响是非单调的，而低温下的超流劲度和正常态电导率则单调增加。在一些器件中，我们发现了与 Berezinskii-Kosterlitz-Thouless 转变一致的直接特征，而在另一些器件中，我们发现超流响应的起始变宽。我们表明，观察到的行为与无序在确定超导 MoS 的性质方面起着重要作用是一致的。我们的工作表明，对于基于剥离片的超导器件，磁性测量是可行的，并且表明超流响应明显偏离简单的 BCS 行为。
