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Phase Asymmetry of Andreev Spectra from Cooper-Pair Momentum

Abhishek Banerjee, Max Geier, Md Ahnaf Rahman, Candice Thomas, Tian Wang, Michael J. Manfra, Karsten Flensberg, Charles M. Marcus

DOI 10.1103/PhysRevLett.131.196301 · Physical Review Letters

T1

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Abstract

In analogy to conventional semiconductor diodes, the Josephson diode exhibits superconducting properties that are asymmetric in applied bias. The effect has been investigated in a number of systems recently, and requires a combination of broken time-reversal and inversion symmetries. We demonstrate a dual of the usual Josephson diode effect, a nonreciprocal response of Andreev bound states to a superconducting phase difference across the normal region of a superconductor-normal-superconductor Josephson junction, fabricated using an epitaxial InAs/Al heterostructure. Phase asymmetry of the subgap Andreev spectrum is absent in the absence of in-plane magnetic field and reaches a maximum at 0.15 T applied in the plane of the junction transverse to the current direction. We interpret the phase diode effect in this system as resulting from finite-momentum Cooper pairing due to orbital coupling to the in-plane magnetic field. At higher magnetic fields, we observe a sign reversal of the diode effect that appears together with a reopening of the spectral gap. Within our model, the sign reversal of the diode effect at higher fields is correlated with a topological phase transition that requires Zeeman and spin-orbit interactions in addition to orbital coupling.

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FormulaReported Tc (K)Pressure (GPa)Type
Al

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—Pressure not reportedunknown

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