Nonlocality of zero-bias anomalies in the topologically trivial phase of Majorana wires

Stãnescu, Tudor D.; Tewari, Sumanta

doi:10.1103/physrevb.89.220507

Cited by 45 publications

(37 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The emergence of trivial low-energy states in systems with non-uniform parameters [25][26][27][28][29]31,32 and in wires coupled to a quantum dot 34 has been discussed extensively in recent years. It was recently argued [33][34][35] that in certain conditions these low-energy trivial states cannot be distinguished from "true" Majorana zero modes localized at the ends of the wire using any type of end-of-the-wire local measurement.…”

Section: B System With An Inhomogeneous Effective Potentialmentioning

confidence: 99%

Effective theory approach to the Schrödinger-Poisson problem in semiconductor Majorana devices

2018

Self Cite

View full text Add to dashboard Cite

We propose a method for solving the Schrödinger-Poisson problem that can be efficiently implemented in realistic 3D tight-binding models of semiconductor-based Majorana devices. The method is based on two key ideas: (i) For a given geometry, the Poisson problem is only solved once (for each local orbital) and the results are stored as an interaction tensor; using this Green's function scheme, the Poisson component of the iteration procedure is reduced to a few simple summations. (ii) The 3D problem is mapped into an effective multi-orbital 1D problem with molecular orbitals calculated self-consistently as the transverse modes of an infinite wire with the same electrostatic potential as the local electrostatic potential of the finite 3D device. These two ideas considerably simplify the numerical complexity of the full 3D Schrödinger-Poisson problem for the nanowire, enabling a tractable effective theory with predictive power. To demonstrate the capabilities of our approach, we calculate the response of the system to an external magnetic field, the dependence of the effective chemical potential on the work function difference, and the dependence of the effective semiconductor-superconductor coupling on the applied gate potential. We find that, within a wide range of parameters, different low-energy bands are characterized by similar effective couplings, which results in induced gap features characterized by a single energy scale. We also find that electrostatic effects are responsible for a partial suppression of the Majorana energy splitting oscillations. Finally, we show that a position-dependent work function difference can produce a non-homogeneous effective potential that is not affected by the screening due to the superconductor and is only partially suppressed by the charge inside the wire. In turn, this potential can induce trivial low-energy states that mimic the phenomenology of Majorana zero modes. Thus any position-dependent work function difference (even at the 1% level) along the nanowire must be avoided through carefully engineered semiconductor-superconductor interfaces.

show abstract

Section: B System With An Inhomogeneous Effective Potentialmentioning

confidence: 99%

Effective theory approach to the Schrödinger-Poisson problem in semiconductor Majorana devices

2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…As it was shown in the Refs. [33] and [34] this model allows clear distinguishing between topologically trivial and Majorana-induced zero-bias peak in the conductance.…”

Section: Modelmentioning

confidence: 99%

Tuning of heat and charge transport by Majorana fermions

Ricco

Dessotti

Shelykh

et al. 2018

Sci Rep

View full text Add to dashboard Cite

We investigate theoretically thermal and electrical conductances for the system consisting of a quantum dot (QD) connected both to a pair of Majorana fermions residing at the edges of a Kitaev wire and two metallic leads. We demonstrate that both quantities reveal pronounced resonances, whose positions can be controlled by tuning of an asymmetry of the couplings of the QD and a pair of MFs. Similar behavior is revealed for the thermopower, Wiedemann-Franz law and dimensionless thermoelectric figure of merit. The considered geometry can thus be used as a tuner of heat and charge transport assisted by MFs.

show abstract

“…We mention that there have been earlier indications that ABSs (or in general, low energy fermionic subgap states) may manifest ZBCP features indistinguishable from MZM-induced zero-bias peak behavior [32][33][34][35][36][37]. In particular, it was shown by a number of authors that the presence of a smooth varying potential background in the nanowire could produce multiple MZMs along the wire (and not just the two pristine MZMs localized at the wire ends), which could lead in some situations to trivial ZBCPs in tunneling measurements mimicking MZMinduced ZBCPs [34][35][36]. The fact that small quantum dot systems could have ABS-induced ZBCPs was experimentally established by Lee et al [32].…”

Section: Introductionmentioning

confidence: 99%

Andreev bound states versus Majorana bound states in quantum dot-nanowire-superconductor hybrid structures: Trivial versus topological zero-bias conductance peaks

et al. 2017

Self Cite

View full text Add to dashboard Cite

Motivated by an important recent experiment [Deng et al., Science 354, 1557], we theoretically consider the interplay between Andreev and Majorana bound states in disorder-free quantum dot-nanowire semiconductor systems with proximity-induced superconductivity in the presence of spin-orbit coupling and Zeeman spin splitting (induced by an external magnetic field). The quantum dot induces Andreev bound states in the superconducting nanowire which show complex behavior as a function of magnetic field and chemical potential, and the specific question is whether two such Andreev bound states can come together forming a robust zero-energy topological Majorana bound state. We find generically that the Andreev bound states indeed have a high probability of coalescing together producing near-zero-energy midgap states as Zeeman splitting and/or chemical potential are increased, but this mostly happens in the nontopological regime below the topological quantum phase transition although there are situations where the Andreev bound states could indeed come together to form a zero-energy topological Majorana bound state. The two scenarios (two Andreev bound states coming together to form a nontopological almost-zero-energy Andreev bound state or to form a topological zero-energy Majorana bound state) are difficult to distinguish just by tunneling conductance spectroscopy since they produce essentially the same tunneling transport signatures. We find that the "sticking together" propensity of Andreev bound states to produce an apparent stable zero-energy midgap state is generic in class D systems in the presence of superconductivity, spin-orbit coupling, and magnetic field, even in the absence of any disorder. We also find that the conductance associated with the coalesced zero-energy nontopological Andreev bound state is non-universal and could easily be 2e 2 /h mimicking the quantized topological Majorana zerobias conductance value. We suggest experimental techniques for distinguishing between trivial and topological zero-bias conductance peaks arising from the coalescence of Andreev bound states.

show abstract

Nonlocality of zero-bias anomalies in the topologically trivial phase of Majorana wires

Cited by 45 publications

References 46 publications

Effective theory approach to the Schrödinger-Poisson problem in semiconductor Majorana devices

Effective theory approach to the Schrödinger-Poisson problem in semiconductor Majorana devices

Tuning of heat and charge transport by Majorana fermions

Andreev bound states versus Majorana bound states in quantum dot-nanowire-superconductor hybrid structures: Trivial versus topological zero-bias conductance peaks

Contact Info

Product

Resources

About