Negative differential thermal conductance and heat amplification in superconducting hybrid devices

Abstract

We investigate the thermal transport properties of a temperature-biased Josephson tunnel junction composed of two different superconductors. We show that this simple system can provide a large negative differential thermal conductance (NDTC) with a peak-to-valley ratio of ∼ 3 in the transmitted electronic heat current. The NDTC is then exploited to outline the caloritronic analogue of the tunnel diode, which can exhibit a modulation of the output temperature as large as 80 mK at a bath temperature of 50 mK. Moreover, this device may work in a regime of thermal hysteresis that can be used to store information as a thermal memory. On the other hand, the NDTC effect offers the opportunity to conceive two different designs of a thermal transistor, which might operate as a thermal switch or as an amplifier/modulator. The latter shows a heat amplification factor > 1 in a 500-mK-wide working region of the gate temperature. After the successful realization of heat interferometers and thermal diodes, this kind of structures would complete the conversion of the most important electronic devices in their thermal counterparts, breaking ground for coherent caloritronics nanocircuits where heat currents can be manipulated at will.

Phase-dependent heat and charge transport through superconductor–quantum dot hybrids

“…Recently, phase-coherent heat transport in superconducting circuits has been observed experimentally [15]. The possibility to control heat currents via magnetic fields has led to a number of proposals for phase-coherent caloritronic devices such as heat interferometers [16,17] and diffractors [18,19], thermal rectifiers [20][21][22][23], transistors [24,25], switches [26] and circulators [27], thermometers [28,29] as well as heat engines [30][31][32] and refrigerators [33,34]. Experimentally, heat interferometers [15,35,36], the quantum diffraction of heat [37], thermal diodes [38] and a thermal router [39] have been realized so far.…”

Nonlinear Critical-Current Thermal Response of an Asymmetric Josephson Tunnel Junction

“…This is the case of the plethora of works descending only recently [3][4][5][6] from the earlier intuition that a temperature bias imposed across a Josephson junction (JJ) produces a phasedependent heat flow through the device [7]. We are dealing with the phase-coherent caloritronics [5,6,8,9], namely, an emerging research field from which fascinating Josephson-based devices, such as heat interferometers [3,10] and diffractors [4,11,12], heat diodes [13] and transistors [14], solid-state memories [15][16][17], microwave refrigerators [18], thermal engines [19], thermal routers [20,21], heat amplifier [22], and heat oscillator [23], were recently designed and actualized. Even the critical current I c of a Josephson tunnel junction, namely, the maximum dissipationless current that can flow through the device, deviates from the well-known Ambegaokar-Baratoff relation [24] in the presence of a thermal bias imposed across the junction, namely, as the superconducting electrodes reside at different temperatures, as portrayed in Fig.…”

“…The abrupt variations are due to the matching in the singularities of the anomalous Green functions in the two * claudio.guarcello@nano.cnr.it superconductors [25]. This feature is the non-dissipative counterpart of the discontinuities discussed in the quasiparticle current flowing through a voltage-biased S 1 IS 2 junction [25,27] and the heat current flowing through a temperature biased junction [14,28], both stemming from the alignment of the singularities of the BCS DOSs in the superconductors [25].…”

Hysteretic Superconducting Heat-Flux Quantum Modulator

“…Hereafter, we set Γ i = 10 −4 ∆ i (0), a value which describes realistic superconducting tunnel junctions [20,21]. Here, ε is the energy measured from the condensate chemical potential, …”