Thermodynamic cycles in Josephson junctions

Abstract

A superconductor/normal metal/superconductor Josephson junction is a coherent electron system where the thermodynamic entropy depends on temperature and difference of phase across the weak-link. Here, exploiting the phase-temperature thermodynamic diagram of a thermally isolated system, we argue that a cooling effect can be achieved when the phase drop across the junction is brought from 0 to π in a iso - entropic process. We show that iso - entropic cooling can be enhanced with proper choice of geometrical and electrical parameters of the junction, i.e. by increasing the ratio between supercurrent and total junction volume. We present extensive numerical calculations using quasi-classical Green function methods for a short junction and we compare them with analytical results. Interestingly, we demonstrate that phase-coherent thermodynamic cycles can be implemented by combining iso - entropic and iso - phasic processes acting on the weak-link, thereby engineering the coherent version of thermal machines such as engines and cooling systems. We therefore evaluate their performances and the minimum temperature achievable in a cooling cycle.

Thermodynamics in topological Josephson junctions

“…Furthermore, it has been shown (employing Hill thermodynamics) that topological phases exhibit unexpected universalities in their thermodynamic signatures [55,56]. Motivated by this and by advances in the understanding of the thermodynamics of non-topological superconductors [57][58][59][60][61][62][63][64][65][66][67][68][69], we have recently applied these thermodynamic concepts to topological Josephson junctions to propose a topological Josephson heat engine [70]. In the same spirit, we discuss another way of utilizing coherent thermodynamics to demonstrate the peculiar nature of topological Josephson junctions: We show that measurements of the phasedependent heat capacity can provide distinct signatures originating from the topological ABS and thus repre-sent an alternative property which can be investigated in topological Josephson junctions.…”

Rashba-controlled thermal valve in helical liquids

“…In this context, a recently emerging field of research revolves around the exploitation of thermal gradients, instead of voltage drops, in nanodevices. The heat and energy flows in nanostructures [34][35][36][37][38][39][40][41][42][43] have hence been addressed. Interesting results have been already obtained within different platforms (using both normal and superconducting nanostructures), demonstrating the coherent control and manipulation of heat flux 34,40,44 .…”

Josephson-Threshold Calorimeter

“…They require fast and ultra-sensitive thermometry [7][8][9][10][11] and cryogenic operating temperatures. Time-resolved photon detection finds applications in many research fields including quantum communication [12], security [13], and quantum thermodynamics [4,[14][15][16][17][18], and is nowadays recently receiving increasing attention.…”