Cr Induced Yu-Shiba-Rusinov States in Superconducting β-Bi₂Pd

Magnetic impurities in superconductors introduce Yu-Shiba-Rusinov (YSR) states within the superconducting gap.

These states are valuable not only for probing fundamental superconducting properties but also may exhibit Majorana

Bound states[1] that have applications in quantum computing[2]. Scanning tunneling spectroscopy (STS) of a single

Cr atom occupying a C_4v symmetric site on the surface of β-Bi₂Pd reveals a single YSR peak with significant electron-

hole asymmetry. We attribute this asymmetry to the underlying bulk band topology.

To accurately model the bulk band topology, we use a multiband (Bi-p and Pd-d w/SOC) ab initio Wannier tight-

binding model. We then compute the real-space normal and anomalous Green's functions in the Nambu 4-spinor basis

and solve the Gor'kov equation for a localized[3] C4v symmetric classical magnetic potential on four surface bismuth

atoms. Our model successfully explains the observed YSR state and naturally reproduces the electron-hole anisotropy

seen in experiments.

This material is based on work supported by the U.S. Department of Energy, Office of Science,

Office of Basic Energy Sciences, under Award No. DE-SC0016379.

[1] C. Mier, J. Hwang, J. Kim, Y. Bae, F. Nabeshima, Y. Imai, A. Maeda, N. Lorente, A. Heinrich, and D.-J.

Choi, Phys. Rev. B 104, 045406 (2021).

[2]C. Nayak, S. H. Simon, A. Stern, M. Freedman, and S. Das Sarma, Rev. Mod. Phys. 80, 1083 (2008).

[3]Michael E. Flatt´e and Jeff M. Byers Phys. Rev. Lett. 78, 3761 (1997)