Gate-tunable superconducting diode effect in a three-terminal Josephson device

Abstract

The phenomenon of non-reciprocal critical current in a Josephson device, termed the Josephson diode effect, has garnered much recent interest. Realization of the diode effect requires inversion symmetry breaking, typically obtained by spin-orbit interactions. Here we report observation of the Josephson diode effect in a three-terminal Josephson device based upon an InAs quantum well two-dimensional electron gas proximitized by an epitaxial aluminum superconducting layer. We demonstrate that the diode efficiency in our devices can be tuned by a small out-of-plane magnetic field or by electrostatic gating. We show that the Josephson diode effect in these devices is a consequence of the artificial realization of a current-phase relation that contains higher harmonics. We also show nonlinear DC intermodulation and simultaneous two-signal rectification, enabled by the multi-terminal nature of the devices. Furthermore, we show that the diode effect is an inherent property of multi-terminal Josephson devices, establishing an immediately scalable approach by which potential applications of the Josephson diode effect can be realized, agnostic to the underlying material platform. These Josephson devices may also serve as gate-tunable building blocks in designing topologically protected qubits.

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

“…Furthermore, the JDE was achieved by engineering higher harmonics in the CPR of a three-terminal JJ network threaded by a magnetic flux. 46 Significant potential of multiterminal JJs lies in the ability to manipulate multiple phase differences. This capability would enable the engineering of an all-flux-tunable Josephson diode, offering versatile device design and control.…”

“…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 …”

Unconventional Superconducting Diode Effects via Antisymmetry and Antisymmetry Breaking

“…For instance, the resistance typically remains unchanged between reversed currents and between inverted magnetic fields. Recently, the superconducting diode effect with one-way supercurrent has gathered significant attention due to its potential for dissipationless electronics. − Such a diode shows zero resistance when current flows in one direction while exhibiting normal resistance when the current is reversed. Its manifestation typically relies on the simultaneous breaking of space inversion and time reversal symmetry. − Notably, the polarity of the diode can be reversed by inverting the applied magnetic field. − This phenomenon is generally described by the magnetochiral anisotropy, which incorporates a nonlinear resistance term ( γ B · I ) that is dependent on both the applied electric current I and the magnetic field B (γ denotes the magnetochiral anisotropy coefficient). − Consequently, a superconducting diode often exhibits a simultaneous nonreciprocal effect in response to both electric currents and magnetic fields.…”

Demonstration of the Nonlocal Josephson Effect in Andreev Molecules

“…The development of high-quality hybrid superconductor–semiconductor materials over the past decade enabled new possibilities in superconducting electronics and quantum computing. − In particular, Andreev bound states (ABSs) − arising in superconductor–semiconductor–superconductor Josephson junctions (JJs) − offer functionalities not attainable in metallic JJs. A prominent example is the electrostatic tuning of the critical current, ,, which allows for JJ field-effect transistors, − voltage-tunable superconducting qubits, − resonators, , and amplifiers. − Moreover, the interplay between ABSs, spin–orbit interaction, and Zeeman fields results in nonreciprocal switching currents − and anomalous phase offsets, or φ 0 -junctions, − with applications in superconducting electronics and spintronics . A yet largely unexplored possibility offered by superconductor–semiconductor hybrids is the engineering of Andreev molecules from the hybridization of spatially overlapping ABSs. − Predicted to arise in JJs coupling over length scales comparable to the superconducting coherence length, Andreev molecules offer a promising platform to realize φ 0 -junctions and novel manipulation and coupling schemes for Andreev qubits .…”