Zernike seminar: Mazhar Ali "The field-free Josephson Diode and One-Directional Superconductivity" - CANCELLED

Nonreciprocal transport is incredibly important in technology; asymmetry in the current-voltage response in semiconductor junctions has been the basis for diodes and transistors,

basic demonstrations of nonreciprocity. Nonreciprocal superconductivity, however, proved elusive, and only in 2020 was the superconducting diode effect (superconducting

in one direction while normal conducting in the other) shown for the first time in an alloy of V/Nb/Ta, using an applied magnetic field. Recently, we demonstrated a Josephson

diode (JD), created in a Quantum Material Josephson Junction (a junction made up of two superconductors separated by a barrier comprised of a quantum material). A diodic effect

was seen without an applied magnetic field; a puzzling result for theoretical physicist and an important for technological application as nanoscale field control remains a challenge.

Using an inversion symmetry breaking heterostructure of NbSe2/Nb3Br8/NbSe2, half-wave rectification was achieved with low switching current density and high rectification

ratio. Following that, a plethora of nonreciprocal QMJJ and other architectures have been investigated and future directions for optimizations and novel explorations will be

discussed, as well as the broader impact of QMJJs, will be discussed.

Ref: The field-free Josephson diode in a van der Waals heterostructure, Nature volume 604, pages653–656 (2022)