QRC Seminar Series - Dr. Francesco Giazotto

Nov 30, 2023
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Francesco Giazotto

Dr. Francesco Giazotto

NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Pisa, Italy

30th November 2023, 11:00am - 12:00pm (GST)


Title:Gate-tunable Josephson junctions go metal: A groundbreaking route towards concrete superconducting electronics
Location:Auditorium 1

In their original formulation of superconductivity, the London brothers predicted more than eighty years ago the exponential suppression of an electrostatic field inside a superconductor over the so-called London penetration depth, in analogy to the Meissner-Ochsenfeld effect. Despite a few experiments indicating hints of perturbation induced by electrostatic gating, no clue has been provided so far on the possibility to manipulate conventional superconductors via gating effect. In this talk, I will report the evidence of full gate-induced control of the supercurrent in all-metallic transistors made of different BCS superconducting thin films [1]. This bipolar field effect persists typically up to ∼ 85% of the critical temperature, and in the presence of sizable magnetic fields. Moreover, I will show the experimental realization of Dayem bridge-based gate-tunable transistors [2-4] able to control the Josephson critical current of the superconducting channel. Finally, I will show the behavior of mesoscopic superconductor-normal metal-superconductor Josephson transistors [5], which will reveal as well the impact of intense gating on proximitized metals. The bipolar supercurrent suppression observed in different systems [6], together with invariant critical temperature and normal-state resistance, excludes conventional charge accumulation/depletion mechanisms. Therefore, the microscopic explanation of this effect calls upon a novel theory able to describe the nontrivial interaction of static electric fields with conventional superconductivity. Besides shedding light on a key issue in physics, these results represent a new paradigm for the realization of an all-metallic superconducting gate-tunable electronics and quantum information architectures based on Josephson circuits. Possible electronic and circuital schemes based on this all-metallic technology will be furthermore discussed

[1] G. De Simoni et al., Nat. Nanotechnol. 13 (2018) 802

[2] F. Paolucci et al., Nano Lett. 18 (2018) 4195

[3] F. Paolucci et al., Phys. Rev. Applied 11 (2019) 024061

[4] F. Paolucci et al., Nano Lett. 19 (2019) 96263

[5] G. De Simoni et al., ACS Nano 13 (2019) 77871

[6] F. Paolucci et al., Nano Lett. (2021),doi.org/10.1021/acs.nanolett.1c03481

Bio:Francesco Giazotto graduated in Physics, and got a PhD in Physics (cum laude) in 2002 at Scuola Normale Superiore in Pisa. He is a research director at Istituto Nanoscienze of CNR in Pisa. He was a visiting scientist for various periods from 2003 to 2008 at Aalto University in Helsinki (FI), and in 2011 at University Joseph Fourier in Grenoble (FR). Dr. Giazotto coordinates as Principal Investigator (PI) the activities of mesoscopic superconductivity, coherent caloritronics, electronic refrigeration, ultrasensitive quantum magnetometry, superconducting spintronics, and quantum transport in hybrid systems at ultralow temperatures at NEST laboratory. He has co-authored 230 articles in international journals, holds 13 patents on superconducting nanodevices, and has given 125 invited talks at national and international conferences. His papers have attracted more than 8170 citations and a 5-years h-index of 45 (Google Scholar). He is also referee of European projects and major international scientific journals. Since 2007 Francesco Giazotto has been PI in 18 projects (7.5 M€), both European and national. For his research activities in the field of thermal transport at the nanoscale he has achieved an ERC Consolidator Grant in 2013, and an ERC PoC Grant in 2020.