Nonlocal Conductance Spectroscopy of Andreev Bound States: Symmetry Relations and BCS Charges

Danon, Jeroen; Hellenes, Anna Birk; Hansen, Esben Bork; Casparis, Lucas; Higginbotham, Andrew; Flensberg, Karsten

doi:10.1103/physrevlett.124.036801

Cited by 96 publications

(100 citation statements)

References 47 publications

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“…The transport within the bulk gap is dominated by the local, Andreev processes, while the main contribution to transport above the bulk gap comes from the nonlocal, direct transmission. The excitation spectrum above the bulk gap contains several series of crossings and avoided crossings, ubiquitous in the spectra of Majorana nanowires [13,15,17,27,[31][32][33]. Our analysis sheds light on the nature of these states' features.…”

Section: Introductionmentioning

confidence: 77%

Linear and nonlinear transport across a finite Kitaev chain: An exact analytical study

et al. 2021

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We present exact analytical results for the differential conductance of a finite Kitaev chain in an N-S-N configuration, where the topological superconductor is contacted on both sides with normal leads. Our results are obtained with the Keldysh nonequilibrium Green's function technique, using the full spectrum of the Kitaev chain without resorting to minimal models. A closed formula for the linear conductance is given, and the analytical procedure to obtain the differential conductance for the transport mediated by higher excitations is described. The linear conductance attains the maximum value of e 2 /h only for the exact zero-energy states. Also, the differential conductance exhibits a complex pattern created by numerous crossings and anticrossings in the excitation spectrum. We reveal the crossings to be protected by inversion symmetry, while the anticrossings result from a pairing-induced hybridization of particlelike and holelike solutions with the same inversion character. Our comprehensive treatment of the Kitaev chain allows us also to identify the contributions of both local and nonlocal transmission processes to transport at arbitrary bias voltage. Local Andreev reflection processes dominate the transport within the bulk gap and diminish for higher excited states but reemerge when the bias voltage probes the avoided crossings. The nonlocal direct transmission is enhanced above the bulk gap but contributes also to the transport mediated by the topological states.

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Section: Introductionmentioning

confidence: 77%

Linear and nonlinear transport across a finite Kitaev chain: An exact analytical study

et al. 2021

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“…(a) However, a recent theoretical work showed that the anti-symmetric components of local an nonlocal conductances are related by [30]…”

Section: Finite-bias Nonlocal Conductance In a Three-terminal Geometrymentioning

confidence: 99%

“…This allows to measure local signatures of MBS such as a resonant zero-bias conductance peak [17][18][19][20][21][22][23][24][25][26][27]. Additionally, a three-terminal setup allows to probe nonlocal conductances, which can provide information about the bulk topology and the BCS charge of bound states [28][29][30].…”

Section: Introductionmentioning

confidence: 99%

“…In twoterminal setups, for example, the conductance is symmetric about the zero bias voltage point, i.e., G(V ) = G(−V ) for |V | < ∆/e [32,33]. In three-terminal setups, it has recently been shown that the anti-symmetric components of the local and nonlocal conductance matrices are equal [30]. However, in experiments these symmetry relations are only observed approximately [34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

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Conductance asymmetries in mesoscopic superconducting devices due to finite bias

et al. 2021

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Tunneling conductance spectroscopy in normal metal-superconductor junctions is an important tool for probing Andreev bound states in mesoscopic superconducting devices, such as Majorana nanowires. In an ideal superconducting device, the subgap conductance obeys specific symmetry relations, due to particle-hole symmetry and unitarity of the scattering matrix. However, experimental data often exhibits deviations from these symmetries or even their explicit breakdown. In this work, we identify a mechanism that leads to conductance asymmetries without quasiparticle poisoning. In particular, we investigate the effects of finite bias and include the voltage dependence in the tunnel barrier transparency, finding significant conductance asymmetries for realistic device parameters. It is important to identify the physical origin of conductance asymmetries: in contrast to other possible mechanisms such as quasiparticle poisoning, finite-bias effects are not detrimental to the performance of a topological qubit. To that end we identify features that can be used to experimentally determine whether finite-bias effects are the source of conductance asymmetries.

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“…On the other hand, ZBCPs in local measurements are sensitive to the details of couplings, and so ought to be less robust with varying parameters and disorder. Experiments that simultaneously detect both local and bulk properties, such as non-local conductance, will help resolve this matter [22][23][24][25][26].…”

mentioning

confidence: 99%

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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Nonlocal Conductance Spectroscopy of Andreev Bound States: Symmetry Relations and BCS Charges

Cited by 96 publications

References 47 publications

Linear and nonlinear transport across a finite Kitaev chain: An exact analytical study

Linear and nonlinear transport across a finite Kitaev chain: An exact analytical study

Conductance asymmetries in mesoscopic superconducting devices due to finite bias

Signatures of a topological phase transition in a planar Josephson junction

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