Time-evolution of photon heat current through series coupled two mesoscopic Josephson junction devices

Abstract

Photon heat current tunneling through a series coupled two mesoscopic Josephson junction (MJJ) system biased by dc voltages has been investigated by employing the nonequilibrium Green’s function approach. The time-oscillating photon heat current is contributed by the superposition of different current branches associated with the frequencies of MJJs ωj (j = 1, 2). Nonlinear behaviors are exhibited to be induced by the self-inductance, Coulomb interaction, and interference effect relating to the coherent transport of Cooper pairs in the MJJs. Time-oscillating pumping photon heat current is generated in the absence of temperature difference, while it becomes zero after time-average. The combination of ωj and Coulomb interactions in the MJJs determines the concrete heat current configuration. As the external and intrinsic frequencies ωj and ω0 of MJJs match some specific combinations, resonant photon heat current exhibits sinusoidal behaviors with large amplitudes. Symmetric and asymmetric evolutions versus time t with respect to ω1t and ω2t are controlled by the applied dc voltages of V1 and V2. The dc photon heat current formula is a special case of the general time-dependent heat current formula when the bias voltages are settled to zero. The Aharonov–Bohm effect has been investigated, and versatile oscillation structures of photon heat current can be achieved by tuning the magnetic fluxes threading through separating MJJs.