Static electric field suppresses superconductivity!

A static electric field can be used to manipulate the superconducting state of metallic superconducting thin films, according to new experiments by researchers in Italy. The effect, which was first put forward by the London brothers, Fritz and Heinz, in their original formulation of superconductivity back in 1935, might be exploited in novel-concept devices such as supercurrent and Josephson field-effect transistors, as well as classical and possibly even quantum bits.

“It seems that we are realizing a novel phase of the superconducting state driven by electric fields”

says Francesco Giazotto of the Consiglio Nazionale delle Ricerche (CNR) and the Scuola Normale Superiore in Pisa, who led this research effort.
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Magnetically-driven colossal supercurrent enhancement in InAs nanowire Josephson junctions

Sample layout and zero magnetic field characterization.

The Josephson effect is a fundamental quantum phenomenon where a dissipationless supercurrent is introduced in a weak link between two superconducting electrodes by Andreev reflections. The physical details and topology of the junction drastically modify the properties of the supercurrent and a strong enhancement of the critical supercurrent is expected to occur when the topology of the junction allows an emergence of Majorana bound states. in the paper by J. Tiira (former Post-Doc student at NEST Laboratory) and collaborators, a group coordinated by Francesco Giazotto from Istituto Nanoscienze, CNR@NEST, has reported on Nature Communication journal charge transport measurements in mesoscopic Josephson junctions formed by InAs nanowires and Ti/Al superconducting leads.

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0–π phase-controllable thermal Josephson junction

Structure of the 0–π phase-tunable thermal Josephson junction.

Two superconductors coupled by a weak link support an equilibrium Josephson electrical current that depends on the phase difference ϕ between the superconducting condensates. Yet, when a temperature gradient is imposed across the junction, the Josephson effect manifests itself through a coherent component of the heat current that flows opposite to the thermal gradient for |ϕ| < π/2. The direction of both the Josephson charge and heat currents can be inverted by adding a π shift to ϕ. In the static electrical case, this effect has been obtained in a few systems, for example via a ferromagnetic coupling or a non-equilibrium distribution in the weak link.

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The ω-SQUIPT as a tool to phase-engineer Josephson topological materials

Low-temperature magnetic flux behavior of the two types of ω-SQUIPTs.

A team composed by researchers from NEST, Centro Mixto CSIC-UPV and Donostia International Physics Center (DIPC) (San Sebastian, Spain), Kavli Institute of Nanoscience (Delft, The Netherlands) has recently published a paper on Nature Nanotechnology journal on a phase-engineered Josephson topological materials topic.

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Nanoscale phase engineering of thermal transport with a Josephson heat modulator

Quantum modulator structure.

Macroscopic quantum phase coherence has one of its pivotal expressions in the Josephson effect, which manifests itself both in charge and energy transport. The ability to master the amount of heat transferred through two tunnel-coupled superconductors by tuning their phase difference is the core of coherent caloritronics, and is expected to be a key tool in a number of nanoscience fields, including solid-state cooling, thermal isolation, radiation detection, quantum information and thermal logic. In this work, Francesco Giazotto and co-workers, from Istituto Nanoscienze and Scuola Normale Superiore at NEST Laboratory show the realization of the first balanced Josephson heat modulator designed to offer full control at the nanoscale over the phase-coherent component of thermal currents.

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