Heat current characteristics in nanojunctions with superconducting baths

Abstract

As a fundamental requisite for thermotronics, controlling heat flow has been a longstanding quest in solid state physics. Recently, there has been a lot of interest in nanoscale hybrid systems as possible candidates for thermal devices. In this context, we study the heat current in the simplest hybrid device of a two level system weakly coupled to two heat baths. We use the reduced density matrix approach together with a simple Born-Markov approximation to calculate the heat current in the steady state. We consider different kinds of reservoirs and show that the nature of the reservoir plays a very important role in determining the thermal characteristics of the device. In particular, we investigate the effectiveness of a conventional superconductor as a reservoir with regard to manipulating the heat current. In the emergent temperature characteristics, we find that superconductivity in the reservoirs leads to enhanced thermal currents and that the superconducting phase transition is clearly visible in the heat current. We observe negative differential thermal conductance and a pronounced rectification of the heat current, making this a good building block for a quantum thermal diode. arXiv:1404.1385v1 [cond-mat.mes-hall]

Thermal rectification with interacting electronic channels: Exploiting degeneracy, quantum superpositions, and interference

“…This has led to proposals of thermal rectifiers based on broken mirror symmetry that use a series of systems with different spectral densities. Recent examples include linear lattices 11 , superconducting junctions [12][13][14][15] , normal-superconducting junctions 16 , metallic islands 17 , quantum Hall tunnel barriers 18 , metaldielectric interfaces 19 , qubits 20,21 , or resonators 22 . Other possiblities include energy-dependent couplings 23 or the asymmetric coupling to a third reservoir acting as an environment with which the system exchanges energy [24][25][26][27][28] .…”

Reversible thermal diode and energy harvester with a superconducting quantum interference single-electron transistor

“…The performance of the device is then controlled by an external parameter, typically a gate voltage. A requirement is the absence of mirror symmetry, which can also be introduced in the spectral properties of the contacts [30][31][32]44,45 .At low temperatures, hybrid metallic-superconducting junctions are interesting candidates as one can make use of the properties of single-electron tunneling in strongly interacting islands 46 and of the energy filtering introduced by the gap of the superconducting contacts. Here we investigate a superconducting quantum interference single-electron transistor (SQUISET), sketched in Fig.…”

“…The performance of the device is then controlled by an external parameter, typically a gate voltage. A requirement is the absence of mirror symmetry, which can also be introduced in the spectral properties of the contacts [30][31][32]44,45 .…”