Selective control of conductance modes in multi-terminal Josephson junctions

Abstract

The Andreev bound state spectra of multi-terminal Josephson junctions form an artificial band structure, which is predicted to host tunable topological phases under certain conditions. However, the number of conductance modes between the terminals of a multi-terminal Josephson junction must be few in order for this spectrum to be experimentally accessible. In this work, we employ a quantum point contact geometry in three-terminal Josephson devices to demonstrate independent control of conductance modes between each pair of terminals and access to the single-mode regime coexistent with the presence of superconducting coupling. These results establish a full platform on which to realize tunable Andreev bound state spectra in multi-terminal Josephson junctions.

Dynamical Stabilization of Multiplet Supercurrents in Multiterminal Josephson Junctions

“…This counterintuitive result provides evidence that multiterminal JJs may host a number of macroscopic quantum phenomena (such as a supercurrent) based solely on the classical nonlinear equations that dictate their dynamics. Our proposed mechanism is consistent with prior work: the visibility of quartet resonances is limited in higher-resistance devices, − but stronger in the lower resistance device of ref . The classically derived cos 2φ term in U (φ) along the resonance could also yield the observed Φ 0 /2 magneto-oscillations in ref .…”

“…Our proposed mechanism is consistent with prior work: the visibility of quartet resonances is limited in higher-resistance devices, 3−5 but stronger in the lower resistance device of ref. 9 The classically derived cos 2φ term in U(φ) along the resonance could also yield the observed Φ 0 /2 magnetooscillations in ref. 8 However, the π − 0 transition observed in that work cannot be explained by our model, and may thus be conclusive evidence of the observation of quartet states.…”

“…For example, in a three-terminal device such as the one shown in Figure a, when V L = − V R ≠ 0, ⟨φ L + φ R ⟩ is stationary with respect to the grounded bottom contact. The microscopic origin of the resulting supercurrent has commonly been attributed to “quartets”, an entangled set of four electrons. − Supercurrents generated by the static phase states exist for any combination of nV L + mV R = 0, with integers n and m and involve the entanglement of multiplets consisting of four or more electrons.…”

Multi-terminal Josephson junctions: A road to topological flux networks

“…Substantial progress has been recently made in this direction, partially fuelled by the perspective of engineering synthetic topology. Several groups have already been able to develop mesoscopic JJs with three or four terminals that exhibited superconducting phase coherent transport in all-metal junctions [40], hybrid semiconductor-superconductor heterostructures [41][42][43][44], graphene [45][46][47] and topological materials [48]. Even a phase-tunable three-terminal Josephson interferometer has been realized [49,50].…”

Nonreciprocal Supercurrents in a Field-Free Graphene Josephson Triode

“…Our devices are based on multiterminal Josephson junctions made in graphene. In the past few years, the multiterminal junctions have been realized in a variety of materials − and have even found a foothold as a solution to technological problems. , …”