Control over epitaxy and the role of the InAs/Al interface in hybrid two-dimensional electron gas systems

Cheah, Erik; Haxell, Daniel Z.; Schott, Rüdiger; Zeng, Peng; Paysen, Ekaterina; Kate, S. C. ten; Coraiola, M.; Landstetter, Max; Zadeh, Ali Baghi; Trampert, A.; Sousa, Marilyne; Riel, Heike; Nichele, Fabrizio; Wegscheider, Werner; Krizek, Filip

doi:10.1103/physrevmaterials.7.073403

Cited by 7 publications

(8 citation statements)

References 59 publications

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“…The device under study, consisting of a multiterminal JJ embedded in double-loop geometry, is displayed in Figure . It was realized in an InAs/Al heterostructure, , where the epitaxial Al layer was selectively removed to expose the III–V semiconductor below. We defined four superconducting terminals, labeled S, L, M, and R, coupled to a common semiconducting region.…”

Section: Resultsmentioning

confidence: 99%

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

Coraiola,

Svetogorov,

Haxell

et al. 2024

ACS Nano

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We investigate the direction-dependent switching current in a flux-tunable four-terminal Josephson junction defined in an InAs/Al two-dimensional heterostructure. The device exhibits the Josephson diode effect with switching currents that depend on the sign of the bias current. The superconducting diode efficiency, reaching a maximum of |η| ≈ 34%, is widely tunable�both in amplitude and sign�as a function of magnetic fluxes and gate voltages. Our observations are supported by a circuit model of three parallel Josephson junctions with nonsinusoidal current−phase relation. With respect to conventional Josephson interferometers, phasetunable multiterminal Josephson junctions enable large diode efficiencies in structurally symmetric devices, where local magnetic fluxes generated on the chip break both time-reversal and spatial symmetries. Our work presents an approach for developing Josephson diodes with wide-range tunability that do not rely on exotic materials.

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Section: Resultsmentioning

confidence: 99%

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

Coraiola,

Svetogorov,

Haxell

et al. 2024

ACS Nano

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“…Experiments were performed on six devices. Figure (a) shows a false-colored scanning electron micrograph of Device 1, the principal device under study, which consisted of a planar SQUID fabricated in a heterostructure of InAs (pink) and epitaxial Al (blue). , The device was covered by a HfO 2 dielectric layer onto which Au gate electrodes (yellow) were deposited. The superconducting loop, defined in the epitaxial Al, contained a superconductor–normal semiconductor–superconductor (SNS) JJ and a narrow Al constriction.…”

Section: Resultsmentioning

confidence: 99%

“…The step-graded metamorphic buffer compensated for the lattice mismatch between the InP and InAs, while the GaAs capping layers provided a barrier for In diffusion into the superconducting layer. The 8 nm InAs layer hosted a two-dimensional electron gas (2DEG), buried 13.4 nm below the semiconductor surface, as measured by transmission electron microscopy . A 15 nm layer of Al was deposited onto the semiconductor surface, in situ without breaking the vacuum in the growth chamber.…”

Section: Methodsmentioning

confidence: 99%

“…Epitaxially grown InAs/Al heterostructures , are a promising platform to realize these complex devices, due to their high electron mobility, excellent superconducting properties, , and prospect of scalability. Such heterostructures have a strong Rashba spin–orbit interaction, , oriented in the plane of the electron gas and perpendicular to the wavevector of charge carriers .…”

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confidence: 99%

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Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions

Haxell,

Coraiola,

Sabonis

et al. 2023

ACS Nano

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We perform supercurrent and tunneling spectroscopy measurements on gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field and report on phase shifts in the current–phase relation measured with respect to an absolute phase reference. The impact of orbital effects is investigated by studying multiple devices with different superconducting lead sizes. At low fields, we observe gate-dependent phase shifts of up to φ 0 = 0.5π, which are consistent with a Zeeman field coupling to highly transmissive Andreev bound states via Rashba spin–orbit interaction. A distinct phase shift emerges at larger fields, concomitant with a switching current minimum and the closing and reopening of the superconducting gap. These signatures of an induced phase transition, which might resemble a topological transition, scale with the superconducting lead size, demonstrating the crucial role of orbital effects. Our results elucidate the interplay of Zeeman, spin–orbit, and orbital effects in InAs/Al JJs, giving improved understanding of phase transitions in hybrid JJs and their applications in quantum computing and superconducting electronics.

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“…Experiments were performed on four devices (Devices 1 to 4) defined in the same epitaxial heterostructure of InAs and Al, , measured in a dilution refrigerator with a base temperature below 10 mK. Figure a shows a false-colored scanning electron micrograph of Device 1, indicating the exposed InAs (pink), the epitaxial Al (blue), the gate electrodes (yellow), and the flux-bias lines (purple).…”

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confidence: 99%

Demonstration of the Nonlocal Josephson Effect in Andreev Molecules

et al. 2023

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We perform switching current measurements of planar Josephson junctions (JJs) coupled by a common superconducting electrode with independent control over the two superconducting phase differences. We observe an anomalous phase shift in the current−phase relation of a JJ as a function of gate voltage or phase difference in the second JJ. This demonstrates the nonlocal Josephson effect, and the implementation of a φ 0junction which is tunable both electrostatically and magnetically. The anomalous phase shift is larger for shorter distances between the JJs and vanishes for distances much longer than the superconducting coherence length. Results are consistent with the hybridization of Andreev bound states, leading to the formation of an Andreev molecule. Our devices constitute a realization of a tunable superconducting phase source and could enable new coupling schemes for hybrid quantum devices.

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Control over epitaxy and the role of the InAs/Al interface in hybrid two-dimensional electron gas systems

Cited by 7 publications

References 59 publications

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

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

Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions

Demonstration of the Nonlocal Josephson Effect in Andreev Molecules

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