Young Scientist Contest 2016 of the Belgian Physical

Young Scientist Contest 2016 of the Belgian Physical Society DIRECT OBSERVATION OF JOSEPHSON VORTICES presented by Lise SERRIER-GARCIA, Tristan CREN, Dimitri RODITCHEV, François DEBONTRIDDER, Christophe BRUN, Juan Carlos CUEVAS, Vagner H. L. BESSA, Milorad MILOŠEVIĆ Institute for Nanoscale Physics and Chemistry, Leuven, Belgium Institut des Nanosciences de Paris, CNRS-UPMC, Paris, France, Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, SPAIN Departement Fysica, Universiteit Antwerpen, BELGIUM

JOSEPHSON EFFECT superconductor Superconducting Quantum Interference Device (SQUID) A very sensitive sensor of extremely subtle magnetic fields mag netic field tunneling barrier The supercurrent is zero at each step of quantum flux. 2

Pb Pb Si Superconductor Non-superconducting metal Insulator normalized conductance SUPERCONDUCTING ELECTRODES Bias voltage (m. V) Using scanning tunneling spectroscopy, we directly access to the local electronic density of states. 3

NANOSTRUCTURES CONTROLLED BY PREPARATION CONDITIONS 1 x 2 x 2µ m² 1 x ) 15 1µ m² 5 26 m he J. C s. 1 19 1 C 20 1( y Ph The lead on silicon growth follows a self-organisation. Temperature, pressure, quality and amount of lead determine the nanostructures. 4

BUILDING A JOSEPHSON JUNCTION nanostructure What? 4 thickness (nm) topography 0 condu ctanc e nanostructure Phys Rev Lett 110 157003 (2013) Bias vo ltage (m V) Superconductivity is not limited to the nanostructures. 5

JOSEPHSON JUNCTION superconductor Josephson junction 1 conductance ctanc condu e conductance map Bias vo ltage (m V) 0 superconductor The distance is reduced to few tens of nanometer creating a Josephson junction. 6

JOSEPHSON JUNCTIONS WITH MAGNETIC FIELD non-supercodnucting metal superconductors magnetic field 1 x 1 y aph pogr to 0 thic ss kne µm² 5 ) (nm Array of Josephson junctions. 7

ABRIKOSOV AND JOSEPSHON VORTICES Nat Phys 11 332 -337 (2015) 1 x 1 µm 2 magnetic field 0 m. T 60 m. T 180 m. T 120 m. T 1 conductance 0 8

THE GINZBURG-LANDAU EQUATIONS Minimizing the free energy of the Ginzburg-Landau theory… Condensation Phys Rev E 86 056709 (2012) Kinetic Nat Phys 11 332 -337 (2015) Magnetic Phys Rev B 65 104515 (2002) … to simulate the Abrikosov vortices. 9

SIMULATING THE SUPERCONDUCTORS… Abrikosov vortex 500 nm 2 H = 120 m. T Josephson junction Nat Phys 11 332 -337 (2015) 2π 1 0 0 amplitude |ψ| phase ϕ Ginzburg-Landau equations describe the superconductivity in the nanostructures but not in the Josephson junctions. 10

… SIMULATING THE JOSEPHSON EFFECT… Phase ϕ Interference pattern J Superconductor 1 Josephson junction Superconductor 0 11

… TO SIMULATE THE JOSEPSHON VORTICES Josephson vortex 500 nm 2 H = 120 m. T Nat Phys 11 332 -337 (2015) 1 1 0 0 superconductivity conductance Simulations and experiments are in very good agreement. 12

JOSEPSHON VORTICES IN ELECTRONIC CIRCUITS Nat Phys 11 332 -337 (2015) Josephson vortices can be induced by supercurrents instead of magnetic field. 13

THANK YOU FOR YOUR ATTENTION!

JOSEPSHON VORTICES AS REAL VORTICES? 1 1 0 0 Currents Superconducting correlations a Josephson vortex corresponds to a quanta of magnetic flux.

AN ELECTRONIC DENSITY OF STATES! x x x superconductor Josephson junction normal layer Abrikosov vortex Josephson vortex x x Josephson vortex cores have a normal state.

ABRIKOSOV VORTICES supercurrents vortex core magnetic field vortices in superconductors An Abrikosov vortex has: a normal core, supercurrents around it, one quantum of magnetic flux.