Impurity-Induced Bound States in Superconductors with Spin-Orbit Coupling

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Superconductivity

Background:

• Superconductors host bound states near magnetic impurities, known as Yu-Shiba-Rusinov (YSR) states.
• Spin-orbit coupling (SOC) is crucial in materials, breaking spin symmetry and influencing electronic properties.

Purpose of the Study:

• Investigate the impact of strong spin-orbit coupling (SOC) on impurity-induced bound states in superconductors.
• Determine how SOC affects the Yu-Shiba-Rusinov (YSR) spectrum in s-wave versus p-wave superconductors.
• Explore the tunability of bound state properties, including fermion parity, via impurity magnetic moment orientation.

Main Methods:

• Theoretical analysis of impurity effects in superconductors with strong spin-orbit coupling.
• Examination of the Yu-Shiba-Rusinov (YSR) state spectrum under varying conditions.
• Study of a dimer of magnetic impurities in both s-wave and p-wave superconducting hosts.

Main Results:

• Spin-orbit coupling (SOC) leads to qualitatively different YSR spectra in s-wave and p-wave superconductors.
• The YSR spectrum is sensitive to the orientation of the impurity's magnetic moment when SOC is present.
• Fermion parity of the lowest energy bound state can be tuned by altering the magnetic moment's orientation.
• Even without SOC, YSR spectra for impurity dimers differ significantly between s-wave and p-wave superconductors.

Conclusions:

• The distinct YSR spectra in the presence of SOC can serve as a signature for identifying superconducting pairing symmetry.
• SOC offers a mechanism to control impurity-induced bound states and their properties in superconductors.
• The study highlights fundamental differences in impurity physics between s-wave and p-wave superconductors, even in the absence of SOC.