Engineering the Floquet spectrum of superconducting multiterminal quantum dots
arXiv:1903.04889 · doi:10.1103/PhysRevB.100.035450
The paper theoretically investigates how periodic driving (Floquet dynamics) creates ladder‑like spectra in superconducting multiterminal quantum‑dot Josephson junctions and shows that these Floquet‑Wannier‑Stark ladders appear as distinct peaks in finite‑frequency current‑current correlations.
Abstract
Here we present a theoretical investigation of the Floquet spectrum in multiterminal quantum dot Josephson junctions biased with commensurate voltages. We first draw an analogy between the electronic band theory and superconductivity which enlightens the time-periodic dynamics of the Andreev bound states. We then show that the equivalent of the Wannier-Stark ladders observed in semiconducting superlattices via photocurrent measurements, appears as specific peaks in the finite frequency current fluctuations of superconducting multiterminal quantum dots. In order to probe the Floquet-Wannier-Stark ladder spectra, we have developed an analytical model relying on the sharpness of the resonances. The charge-charge correlation function is obtained as a factorized form of the Floquet wave-function on the dot and the superconducting reservoir populations. We confirm these findings by Keldysh Green's function calculations, in particular regarding the voltage and frequency dependence of the resonance peaks in the current-current correlations. Our results open up a road-map to quantum correlations and coherence in the Floquet dynamics of superconducting devices.
13 pages, 7 figures, Supplemental Material as ancillary file (7 pages), revised manuscript, Physical Review Editors' suggestion