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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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“Nonlocal thermoelectricity in a topological Josephson junction” just published on “Physical Review Letters”

Sketch of the setup used to probe the nonlocal Thermoelectricity in a topological Josephson junction Sketch of the setup used to probe the nonlocal Thermoelectricity in a topological Josephson junction

In a paper just published on Physical Review Letters, a NEST-CNR-NANO team lead by SQEL member Alessandro Braggio identified a unique non-local thermoelectrical effect in a Quantum spin Hall system in 2-dimensional topological insulators, proximized with superconductors, also called topological Josephson junctions.

The quantum spin Hall state is characterised by Kramer paired helical edge states which propagate in opposite directions with opposite spin orientations (spin-momentum locking). Unambiguous identification of those edge state is fundamental to certify their topological nature and has prominent implications in condensed matter research and its applications in topological quantum computation and sensing.

The team, composed by Gianmichele Blasi, Fabio Taddei, Matteo Carrega and coordinated by Alessandro Braggio from SQEL and NEST laboratory (Scuola Normale Superiore and CnrNano) collaborating with Liliana Arrachea from ECyT-UNSAM (Argentina), investigated a three-terminal setup with helical edge states proximized by two superconductors and contacted with a normal-metal probe, in the presence of an external magnetic field. Since the whole system is particle-hole symmetric, nonlocality is the only way to generate linear thermoelectricity. Nonlocal thermoelectrical transport is generated in the probe by applying a thermal gradient between the superconductors.

Blasi, G., Taddei, F., Arrachea, L., Carrega, M., & Braggio, A. (2020). Nonlocal Thermoelectricity in a S-TI-S Junction in Contact with a N-Metal Probe: Evidence for Helical Edge States. Physical Review Letters, 124(22), 227701. DOI: https://doi.org/10.1103/PhysRevLett.124.227701. arXiv: http://arxiv.org/abs/1911.04367

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SQEL at the Nanowire Week 2019

Elia Strambini during his talk at Nanowire Week 2019 Elia Strambini during his talk at Nanowire Week 2019

The Nanowire Week is one of the biggest conferences on nanowires merging two well-established and highly successful annual workshops: NANOWIRES and the Nanowire Growth Workshop. The 2019 edition has been held in Pisa from September 23 to 27 organized by NEST, Scuola Normale Superiore and CNR Istituto Nanoscienze.

Our researcher Elia Strambini presented some unpublished results of our group in a a talk titled “Magnetically-driven anomalous phase shift in InAs nanowire Josephson Junctions” about the revealing of an anomalous phase shift in a Al/InAs(NW)/Al Josephson junction.

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“Field-Effect Controllable Metallic Josephson Interferometer” published on Nano Letters

“Field-Effect Controllable Metallic Josephson Interferometer” published on Nano Letters “Field-Effect Controllable Metallic Josephson Interferometer” published on Nano Letters

A new research carried out at the SQEL report the realization of a titanium-based monolithic superconducting quantum interference device (SQUID) which can be tuned by applying a gate bias to its two Josephson junctions.

The research, published on Nano Letters by F. Paolucci and co-authors, points out the strong implications of the apparent coupling of a static electric field to the macroscopic phase of the superconducting condensate.

Beyond that, this class of quantum interferometers could represent a breakthrough for several applications such as digital electronics, quantum computing, sensitive magnetometry, and single-photon detection.