Spectrum of Andreev Bound States in a Molecule Embedded Inside a Microwave-Excited Superconducting Junction
Journal article, 2008
Non-dissipative Josephson current through nanoscale
superconducting constrictions is carried by spectroscopically sharp
energy states, so-called Andreev bound 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.