标题： 安德列夫与非常规平带超导体的隧穿谱学 显示英文标题

标题： Andreev versus Tunneling Spectroscopy of Unconventional Flat Band Superconductors

摘要： 扫描隧道显微镜（STM）实验在基于石墨烯的莫尔超导体（SC）的隧穿和安德烈夫区域显示了两个不同的能量尺度，其起源尚不清楚。 我们用格林函数表示正常-超导体（SC）界面的电导率，这使我们能够从两个方面更清晰地探讨这些问题。 首先，我们表明这两个不同的能量尺度不能通过隧穿中的赝能隙和安德烈夫谱中的超导能隙来理解。 其次，STM探针和拓扑带SC之间的大费米速度vF失配会使透明界面向隧穿区域转变，而在莫尔SC中无法实现弹道安德烈夫区域。 我们还讨论了影响电导率的自能修正对vF的影响。 最后，我们通过将安德烈夫实验建模为嵌入非常规SC中的圆形金属盘来解决这些问题。 我们表明，在强vF失配的情况下，低偏压电导率由探针在与非常规SC界面处诱导的安德烈夫束缚态主导。 这些安德烈夫束缚态产生了安德烈夫实验中观察到的低能尺度，该尺度小于隧穿光谱中的SC能隙。 显示英文摘要

摘要： STM experiments in the tunneling and Andreev regimes on graphene-based moire superconductors (SC) show two distinct energy scales whose origin is mysterious. We express the conductance of a normal-SC interface in terms of Green's functions, which allows us to sharpen the issues in two ways. First, we show that the two distinct energy scales cannot be understood in terms of a pseudogap in tunneling and a superconducting gap in the Andreev spectra. Second, the large Fermi velocity vF mismatch between the STM tip and the at band SC renormalizes a transparent interface towards the tunneling regime, and the ballistic Andreev regime cannot be realized in moire SCs. We also discuss self energy corrections to vF that determines the conductance. Finally, we offer a resolution to these problems by modeling the Andreev experiment as a circular metallic disc embedded in an unconventional SC. We show that with strong vF mismatch the low bias conductance is dominated by Andreev bound states induced by the tip at the interface with the unconventional SC. The ABS give rise to the low energy scale seen in Andreev experiments, smaller than the SC gap in tunneling spectroscopy.