Inductive microwave response of Yu-Shiba-Rusinov states

We calculate the frequency-dependent admittance of a phase-biased Josephson junction spanning a magnetic impurity or a spinful Coulomb-blockaded quantum dot. The local magnetic moment gives rise to Yu-Shiba-Rusinov bound states, which govern the subgap absorption as well as the inductive response. We model the system by a superconducting spin-polarized exchange-cotunnel junction and calculate the linear current response to an ac bias voltage, including its dependence on phase bias as well as particle-hole and source-drain coupling asymmetry. The corresponding inductive admittance is analyzed and compared to results of a zero bandwidth, as well as an infinite-gap approximation to the superconducting Anderson model. All three approaches capture the interaction-induced 0-pi transition, which is reflected as a discontinuity in the adiabatic inductive response.

Automated summary

In this study, we investigated the frequency-dependent admittance of a phase-biased Josephson junction spanning a magnetic impurity or a spinful Coulomb-blockaded quantum dot. The local magnetic moment led to the emergence of Yu-Shiba-Rusinov bound states, which influenced subgap absorption and inductive response. Modeling the system as a superconducting spin-polarized exchange-cotunnel junction, we calculated the linear current response to an ac bias voltage, considering phase bias, particle-hole symmetry, and source-drain coupling asymmetry. The analysis of the corresponding inductive admittance revealed features consistent with interaction-induced 0-pi transition.