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“A thermal superconducting quantum interference proximity transistor ” published on Nature Physics

Thermal superconducting quantum interference proximity transistor Thermal superconducting quantum interference proximity transistor

Researchers at SQEL have recently developed a transistor that takes advantage of this specific quality of superconductors, a thermal superconducting quantum interference proximity transistor (T-SQUIPT) published on Nature Physics.

T-SQUIPT was first theoretically proposed by some of the authors of our recent paper several years ago, although without a concrete realization yet. Our implementation of the T-SQUIPT exploits a long superconducting nanowire as proximitized element thus allowing us to demonstrate the possibility to phase-tune the thermal transport properties of a superconductor and to realize the first thermal memory cell as well.

The core concept of T-SQUIPT is a nanoscopic island of aluminum (Al) that can be made superconducting- or normal metal-like with quantum interference induced by two superconducting leads defining a ring and placed in good metallic contact with the island. For integer values of the flux quantum piercing the superconducting loop, superconductivity is reinforced and the island behaves as a good thermal insulator. For semi-integer values of the flux quantum, superconductivity is ideally suppressed, and the island behaves as a good thermal conductor.

As part of their recent study, SQEL researchers demonstrated this ability of their transistor by sinking heat from a metallic electrode into it, which was also coupled to the aluminum island through a tunnel contact. Overall, our findings demonstrate the feasibility of phase-coherently manipulating the energy transport qualities of quantum devices.

In the future, the T-SQUIPT transistor could pave the way towards the realization of a variety of new devices. The recent paper also enhances the current understanding of energy transfer at the nanoscale, thus potentially improving its management.

More information: Nadia Ligato et al, Thermal superconducting quantum interference proximity transistor, Nature Physics (2022). DOI: 10.1038/s41567-022-01578-z

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“Nonlinear thermoelectricity with electron-hole symmetric systems” published on Physical Review Letters

“Nonlinear thermoelectricity with electron-hole symmetric systems” published on Physical Review Letters

Recently thermoelectric systems have been extensively investigated since the growing interests in the field of quantum thermodynamics and in studying of thermal transport at the nanoscale.

In a two-terminal system, a necessary condition for thermoelectricity in the linear regime – i.e., for a small voltage V and a small temperature bias ∆T – is breaking the electron-hole symmetry which results in the transport property I(V, ∆T) ≠ −I(−V, ∆T), where I is the charge current flowing through the two-terminal system.

In a new research paper “Nonlinear thermoelectricity with electron-hole symmetric systems” published on “Physical Review Letters” by G. Marchegiani, A. Braggio e F. Giazotto, we demonstrate that this condition is no longer required outside the linear regime. Even a prototype system like a tunnel junction between two different superconductors, can exhibit nonlinear thermo-electric effect based on the spontaneous breaking of electron-hole symmetry in the system.

“The next step will be the experimental realization of this effect and further theoretical investigations of this new discovered mechanism”.

commented F. Giazotto

Check out also the Italian press release!