Thermal superconducting quantum interference proximity transistor

Superconductors are excellent thermal insulators at low temperatures owing to the presence of an energy gap in their density of states 1 . Through the so-called proximity effect 2 , superconductors can influence the density of states of nearby metallic or superconducting wires. In this way, the local density of states of a wire can be tuned by controlling the phase bias ( φ ) imposed across it 3 . Here we demonstrate a thermal superconducting quantum interference proximity transistor (T-SQUIPT) that enables the phase control of heat currents by exploiting the superconducting proximity effect. Our T-SQUIPT device comprises a quasi-one-dimensional aluminium nanowire forming the weak link embedded in a superconducting ring 4 , 5 . Controlling the phase bias by changing the magnetic flux through the ring shows temperature modulations of up to 16 mK, yielding a temperature-to-flux transfer function that reaches approximately 60 mK Φ 0 –1 . We also demonstrate a hysteretic dependence of the local density of states of T-SQUIPTs on the applied magnetic field due to phase-slip transitions. This allows the T-SQUIPT device to operate as a phase-tunable thermal memory 6 , 7 , where the information is encoded in the temperature of the metallic mesoscopic island.