Subgap dynamics of double quantum dot coupled between superconducting and normal leads

TL;DR

This paper studies the time-dependent charge dynamics in a double quantum dot system connected to superconducting and normal leads, revealing complex oscillatory behaviors relevant for superconducting qubit design.

Contribution

It provides a detailed analysis of subgap dynamical responses in a double quantum dot coupled to superconducting and normal reservoirs under various time-dependent perturbations.

Findings

Identification of multi-mode oscillations and beating patterns in charge currents

Observation of photon-assisted harmonics in the dynamical response

Insights into quasiparticle signatures in time-dependent measurements

Abstract

Dynamical processes induced by the external time-dependent fields can provide valuable insight into the characteristic energy scales of a given physical system. We investigate them here in a nanoscopic heterostructure, consisting of the double quantum dot coupled in series to the superconducting and the metallic reservoirs, analyzing its response to (i)~abrupt bias voltage applied across the junction, (ii) sudden change of the energy levels, and imposed by (iii)~their periodic driving. We explore subgap properties of this setup which are strictly related to the in-gap quasiparticles and discuss their signatures manifested in the time-dependent charge currents. The characteristic multi-mode oscillations, their beating patters and photon-assisted harmonics reveal a rich spectrum of dynamical features that might be important for designing the superconducting qubits.