Phase engineering of anomalous Josephson effect derived from Andreev molecules

Abstract

A Josephson junction (JJ) is a key device for developing superconducting circuits, wherein a supercurrent in the JJ is controlled by the phase difference between the two superconducting electrodes. When two JJs sharing one superconducting electrode are coherently coupled and form the Andreev molecules, a supercurrent of one JJ is expected to be nonlocally controlled by the phase difference of another JJ. Here, we evaluate the supercurrent in one of the coupled two JJs as a function of local and nonlocal phase differences. Consequently, the results exhibit that the nonlocal phase control generates a finite supercurrent even when the local phase difference is zero. In addition, an offset of the local phase difference giving the JJ ground state depends on the nonlocal phase difference. These features demonstrate the anomalous Josephson effect realized by the nonlocal phase control. Our results provide a useful concept for engineering superconducting devices such as phase batteries and dissipationless rectifiers.

Flux-Tunable Josephson Diode Effect in a Hybrid Four-Terminal Josephson Junction

“…Hybridization of ABSs was shown to distort the CPR of individual JJs based on the phase tuning of nearby JJs. 39 − 41 In the present devices, hybridization between ABSs was demonstrated by means of local tunneling spectroscopy 51 between two modes in the L–M and M–R JJs. Since the terminals L, M, and R are shorted by superconducting loops, the ABSs hosted by the L–M and M–R junctions do not contribute to the switching current measured from S to D. Nevertheless, our devices could host more ABSs between S and the other leads that hybridize, giving rise to phase shifts and amplitude modulations in the CPR of individual JJs.…”

“…Initial experiments identified the JDE and ascribed it to phase-drag effects . Coupling between JJs hosting ABSs realizes Andreev molecules, − which also give rise to the JDE. , Another line of research focused on multiterminal devices featuring more than two current ports. , In this configuration, a bias current applied to one lead controls the switching current and its nonreciprocity measured between two other leads. Furthermore, the JDE was achieved by engineering higher harmonics in the CPR of a three-terminal JJ network threaded by a magnetic flux …”

“…Initial experiments 37 identified the JDE and ascribed it to phase-drag effects. 38 Coupling between JJs hosting ABSs realizes Andreev molecules, 39 − 41 which also give rise to the JDE. 42 , 43 Another line of research focused on multiterminal devices featuring more than two current ports.…”