Szczęśniak Dominik, Kais Sabre
Department of Chemistry, Purdue University, 560 Oval Dr., West Lafayette, IN, 47907, USA.
Department of Theoretical Physics, Faculty of Science and Technology, Jan Długosz University in Częstochowa, 13/15 Armii Krajowej Ave., 42200, Czestochowa, Poland.
Sci Rep. 2021 Jan 19;11(1):1813. doi: 10.1038/s41598-021-81450-x.
In the present study we investigate the selected local aspects of the metal-induced gap states (MIGSs) at the disordered metal-insulator interface, that were previously proposed to produce magnetic moments responsible for the magnetic flux noise in some of the superconducting qubit modalities. Our analysis attempts to supplement the available studies and provide new theoretical contribution toward their validation. In particular, we explicitly discuss the behavior of the MIGSs in the momentum space as a function of the onsite energy deviation, that mimics random potential disorder at the interface in the local approximation. It is found, that when the difference between the characteristic electronic potentials in the insulator increases, the corresponding MIGSs become more localized. This effect is associated with the increasing degree of the potential disorder that was earlier observed to produce highly localized MIGSs in the superconducting qubits. At the same time, the presented findings show that the disorder-induced localization of the MIGSs can be related directly to the decay characteristics of these states as well as to the bulk electronic properties of the insulator. As a result, our study reinforces plausibility of the previous corresponding investigations on the origin of the flux noise, but also allows to draw future directions toward their better verification.
在本研究中，我们研究了无序金属-绝缘体界面处金属诱导能隙态（MIGSs）的选定局部方面，这些能隙态先前被认为会产生磁矩，而磁矩是某些超导量子比特模态中磁通噪声的原因。我们的分析试图补充现有研究，并为其验证提供新的理论贡献。特别是，我们明确讨论了MIGSs在动量空间中作为在位能偏差函数的行为，在位能偏差在局部近似中模拟了界面处的随机势无序。研究发现，当绝缘体中特征电子势之间的差异增加时，相应的MIGSs会变得更加局域化。这种效应与势无序程度的增加有关，此前在超导量子比特中观察到势无序程度增加会产生高度局域化的MIGSs。同时，研究结果表明，MIGSs的无序诱导局域化可能与这些态的衰减特性以及绝缘体的体电子性质直接相关。因此，我们的研究增强了先前关于磁通噪声起源的相应研究的合理性，同时也为更好地验证这些研究指明了未来方向。
