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arXiv 2012.01490cond-mat.supr-concond-mat.mes-hall
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门控超导相的光谱特征

Spectroscopic Signatures of Gate-Controlled Superconducting Phases

Maria Teresa Mercaldo, Francesco Giazotto, Mario Cuoco

摘要:

我们研究了超导体-绝缘体-正常金属(SIN)和超导体-绝缘体-超导体(SIS)异质结的隧穿电导,该异质结的超导侧是电驱动的,并且通过修改表面反转非对称耦合可以表现出$π$配对。在SIN隧穿过程中,我们发现电驱动相互作用的变化通常会导致带隙中准粒子的增加,这是由于轨道极化的缺对态,而与带间相位重排无关。在间隙边缘的SIN电导的峰值随依赖于表面相互作用的强度以及栅极诱导的超导状态的特性的趋势而变化。虽然这种偏移也可以与SIN配置中的热效应相关联,但是对于低温下的SIS几何形状,电场在与超导电极的间隙之间的差相关的电压处不产生特征匹配峰。这一观察为光谱学区分热布居效应和量子门驱动的特征提供了一个独特的标志。在SIS中,静电门产生了各种特征,具有不对称的峰和电导谱权重的加宽。这些研究结果表明SIN和SIS隧穿光谱的一般定性趋势,可以用来评估门控对超导体的影响和非中心对称轨道反相配对的发生。

英文摘要:

We investigate the tunneling conductance of superconductor-insulator-normal metal (SIN) and superconductor-insulator-superconductor (SIS) heterostructures with one superconducting side of the junction that is electrically driven and can exhibit $π$-pairing through a modification of the surface inversion asymmetric couplings. In SIN tunneling we find that the variation of the electrically driven interactions generally brings an increase of quasi-particles in the gap due to orbitally polarized depaired states, irrespective of the inter-band phase rearrangement. The peak of SIN conductance at the gap edge varies with a trend that depends both on the strength of the surface interactions as well as on the character of the gate-induced superconducting state. While this shift can be also associated with thermal effects in the SIN configuration, for the SIS geometry at low temperature the electric field does not yield the characteristic matching peak at voltages related with the difference between the gaps of the superconducting electrodes. This observation sets out a distinctive mark for spectroscopically distinguishing the thermal population effects from the quantum gate-driven signatures. In SIS the electrostatic gating yields a variety of features with asymmetric peaks and broadening of the conductance spectral weight. These findings indicate general qualitative trends for both SIN and SIS tunneling spectroscopy which could serve to evaluate the impact of gate-control on superconductors and the occurrence of non-centrosymmetric orbital antiphase pairing.

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