Josephson Inductance as a Probe for Highly Ballistic Semiconductor-Superconductor Weak Links

We present simultaneous measurements of Josephson inductance and dc transport characteristics of ballistic Josephson junctions based upon an epitaxial Al-InAs heterostructure. The Josephson inductance at finite current bias directly reveals the current-phase relation. The proximity-induced gap, the critical current and the average value of the transparency (tau) over bar are extracted without need for phase bias, demonstrating, e.g., a near-unity value of (tau) over bar = 0.94. Our method allows us to probe the devices deeply in the nondissipative regime, where ordinary transport measurements are featureless. In perpendicular magnetic field the junctions show a nearly perfect Fraunhofer pattern of the critical current, which is insensitive to the value of (tau) over bar. In contrast, the signature of supercurrent interference in the inductance turns out to be extremely sensitive to (tau) over bar.

Automated summary

Simultaneous measurements of Josephson inductance and dc transport characteristics in ballistic Josephson junctions reveal important parameters without the need for phase bias. The method allows for deep probing of devices in the nondissipative regime, showing sensitivity to specific characteristics such as supercurrent interference.