Relating Andreev Bound States and Supercurrents in Hybrid Josephson Junctions

Nichele, Fabrizio; Portolés, Elías; Fornieri, Antonio; Whiticar, Alexander; Drachmann, A. C. C.; Gronin, Sergei; Wang, T.; Gardner, Geoffrey C.; Thomas, Candice; Hatke, A. T.; Manfra, Michael J.; Marcus, C. M.

doi:10.1103/physrevlett.124.226801

Cited by 80 publications

(56 citation statements)

References 33 publications

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“…The inductance of the superconducting loop is a combination of the geometric inductance and the kinetic inductance of the thin Al layer, and is dominated by the latter [18]. We estimate the geometric inductance of the loop as L G ∼ 2.5 pH.…”

Section: Estimation Of Flux Loop Inductancementioning

confidence: 98%

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Signatures of a topological phase transition in a planar Josephson junction

Banerjee¹,

Lesser²,

Rahman³

et al. 2022

Preprint

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A growing body of work suggests that planar Josephson junctions fabricated using superconducting hybrid materials provide a highly controllable route toward one-dimensional topological superconductivity. Among the experimental controls are in-plane magnetic field, phase difference across the junction, and carrier density set by electrostatic gate voltages. Here, we investigate planar Josephson junctions with an improved design based on an epitaxial InAs/Al heterostructure, embedded in a superconducting loop, probed with integrated quantum point contacts (QPCs) at both ends of the junction. For particular ranges of in-plane field and gate voltages, a closing and reopening of the superconducting gap is observed, along with a zero-bias conductance peak (ZBCP) that appears upon reopening of the gap. Consistency with a simple theoretical model supports the interpretation of a topological phase transition. While gap closings and reopenings generally occurred together at the two ends of the junction, the height, shape, and even presence of ZBCPs typically differed between the ends, presumably due to disorder and variation of couplings to local probes.

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Section: Estimation Of Flux Loop Inductancementioning

confidence: 98%

“…The maximum (minimum) induced gap is ∆ ∼ 80 µeV (50µeV) at integer (half-integer) flux through the loop. Around half flux quantum values, sharp switches are observed, which we attribute to phase slips due to the large inductance of the loop, L ∼ 2 nH [18] (see Methods).…”

mentioning

confidence: 91%

Signatures of a topological phase transition in a planar Josephson junction

Banerjee¹,

Lesser²,

Rahman³

et al. 2022

Preprint

Self Cite

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“…( 1) to L 1 = ∆Φ s /2I 1 , as n 2 is tuned. We extract an inductance at base temperature (where it is expected to be lowest 27 ) L 1 of the order of 2 µH, orders of magnitude higher than in other 2D superconductors 27 or narrow 3D SQUID geometries 28 . The geometric contribution to the inductance L is negligible compared to the measured values, confirming the inductance of the device to be mainly of kinetic origin (see Methods).…”

mentioning

confidence: 99%

A Tunable Monolithic SQUID in Twisted Bilayer Graphene

Portolés¹,

Iwakiri²,

Zheng³

et al. 2022

Preprint

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“…The GJJ allows the Josephson supercurrent by forming Andreev bound states (ABSs) of electron-and hole-like quasi-particles in the graphene, which are correlated by Andreev reflections at the graphene/superconductor interfaces. In the short junction limit where GJJ channel length L is much shorter than the superconducting coherence length = ℏ / ABS , a single pair of ABSs forms within the superconducting gap of ohmiccontacted Al electrodes ABS and oscillates with the macroscopic quantum phase difference between two superconductors as ± ( ) = ABS √(1 − sin 2 ( /2)) [26][27][28][29] . Here, ℏ is a reduced Planck's constant, =10 6 ms −1 is the Fermi velocity of graphene, and D is the contact transparency.…”

mentioning

confidence: 99%

Steady Floquet-Andreev States Probed by Tunnelling Spectroscopy

Lee¹,

Park²,

Lee³

et al. 2021

Preprint

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Engineering quantum states through light-matter interaction has created a new paradigm in condensed matter physics. A representative example is the Floquet-Bloch state, which is generated by time-periodically driving the Bloch wavefunctions in crystals. Previous attempts to realise such states in condensed matter systems have been limited by the transient nature of the Floquet states produced by optical pulses, which masks the universal properties of non-equilibrium physics. Here, we report the generation of steady Floquet Andreev (F-A) states in graphene Josephson junctions by continuous microwave application and direct measurement of their spectra by superconducting tunnelling spectroscopy. We present quantitative analysis of the spectral characteristics of the F-A states while varying the phase difference of superconductors, temperature, microwave frequency and power. The oscillations of the F-A state spectrum with phase difference agreed with our theoretical calculations. Moreover, we confirmed the steady nature of the F-A states by establishing a sum rule of tunnelling conductance, and analysed the spectral density of Floquet states depending on Floquet interaction strength. This study provides a basis for understanding and engineering non-equilibrium quantum states in nano-devices.

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Relating Andreev Bound States and Supercurrents in Hybrid Josephson Junctions

Cited by 80 publications

References 33 publications

Signatures of a topological phase transition in a planar Josephson junction

Signatures of a topological phase transition in a planar Josephson junction

A Tunable Monolithic SQUID in Twisted Bilayer Graphene

Steady Floquet-Andreev States Probed by Tunnelling Spectroscopy

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