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The field-free Josephson diode in a van der Waals heterostructure

Date: 2022-09-15
Time: 16:00
Venue: Online Seminar
Speaker: Dr. Heng Wu

(Delft University of Technology)

Zoom Meeting ID: 825 5116 9800

Passcode: 451697

报告摘要:

The superconducting analog to the semiconducting diode, the Josephson diode, has long been sought with multiple avenues to realization proposed by theorists. Exhibiting magnetic field free, single directional superconductivity with Josephson coupling, it would serve as the building block for next generation superconducting circuit technology. Here we realized the Josephson diode by fabricating an inversion symmetry breaking van der Waals heterostructure of NbSe2/Nb3Br8/NbSe2. We demonstrate, for the first time without magnetic field, that the junction can be superconducting with positive current while resistive with negative current. The DIc behavior (the difference between positive and negative critical currents) with magnetic field is symmetric and Josephson coupling is proven through the Fraunhofer pattern. Also, stable half-wave rectification of a square-wave excitation was achieved with a very low switching current density, high rectification ratio and high robustness. This nonreciprocal behavior strongly violates the known Josephson relations and opens the door to discover new mechanisms and physical phenomena through integration of quantum materials with Josephson junctions, and provides new avenues for superconducting quantum devices.

References:

1.Hu, J., Wu, C. & Dai, X. Proposed design of a Josephson diode. Phys. Rev. Lett. 99, 067004 (2007).

2. Kou M. & Nagaosa, N. Theory of the nonreciprocal Josephson effect. Phys. Rev. B 103, 245302 (2021).

3. Wu, Heng et al. The field-free Josephson diode in a van der Waals heterostructure. Nature 604, 653–656 (2022)

邀请人:沈洁特聘研究员/蒋坤特聘研究员