YBa2Cu3O7 Josephson diode fabricated by focused-helium-ion-beam irradiation

Abstract

Using a focused He+ beam for nanopatterning and writing of Josephson barriers, we fabricated specially shaped Josephson junctions of in-line geometry in YBa2Cu3O7 thin film microbridges with an asymmetry ratio of critical currents of opposite polarities of approximately 7 at the optimum magnetic field. Those Josephson diodes were subsequently used as ratchets to rectify an applied alternating current into a dc voltage. We also demonstrate the operation of such a ratchet in the loaded regime, where it produces a nonzero dc output power and yields a thermodynamic efficiency of up to 75%. The ratchet shows record figures of merit: an output dc voltage of up to 212μV and an output power of up to 0.2nW. The device has an essential area of approximately 1μm2. For rectification of quasistatic Gaussian noise, the figures of merit are more modest; however, the efficiency can be as high as for the deterministic ac drives within some regimes. Since the device is based on YBa2Cu3O7, it can operate at temperatures up to approximately 40K, where more noise is available for rectification.

Source-reported materials — not catalogue approval

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