Spectrum of Andreev bound states in a molecule embedded inside a microwave-excited superconducting junction.
Nondissipative Josephson current through nanoscale superconducting constrictions is carried by spectroscopically sharp energy states, the so-called Andreev states. Although theoretically predicted almost 40 years ago, no direct spectroscopic evidence of these Andreev bound states exists to date. We propose a novel type of spectroscopy based on embedding a superconducting constriction, formed by a single-level molecule junction, in a microwave QED cavity environment. In the electron-dressed cavity spectrum we find a polariton excitation at twice the Andreev bound state energy, and a superconducting-phase-dependent ac Stark shift of the cavity frequency. Dispersive measurement of this frequency shift can be used for Andreev bound state spectroscopy.
Sköldberg
Jonas
J
Department of Microtechnology and Nanoscience--MC2, Chalmers University of Technology, S-412 96 Göteborg, Sweden.
Löfwander
Tomas
T
Shumeiko
Vitaly S
VS
Fogelström
Mikael
M