Topologically trivial zero-bias conductance peak in semiconductor Majorana wires from boundary effects

Roy, Dibyendu; Bondyopadhaya, Nilanjan; Tewari, Sumanta

doi:10.1103/physrevb.88.020502

Cited by 93 publications

(76 citation statements)

References 46 publications

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“…The reasons for this discrepancy are addressed in Refs. 39,40 , and alternative non-topological explanations have been advanced [41][42][43][44][45][46] . The lack of quantization of the experimental observations can be reconciled 5,39 with the Majorana theory by including the finite temperature and the finite length of the nanowire (thus allowing the Majorana modes from the two ends to overlap), but this physics is beyond the scope of our work where we restrict to zero temperature and a single normal metal-superconductor (NS) junction (assuming the other Majorana mode to be far away from this junction).…”

Section: Introductionmentioning

confidence: 99%

Conductance spectroscopy of topological superconductor wire junctions

Setiawan

Brydon

et al. 2015

Phys. Rev. B

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We study the zero-temperature transport properties of one-dimensional normal metalsuperconductor (NS) junctions with topological superconductors across their topological transitions. Working within the Blonder-Tinkham-Klapwijk (BTK) formalism generalized for topological NS junctions, we analytically calculate the differential conductance for tunneling into two models of a topological superconductor: a spinless intrinsic p-wave superconductor and a spin-orbit-coupled s-wave superconductor in a Zeeman field. In both cases we verify that the zero-bias conductance is robustly quantized at 2e 2 /h in the topological regime, while it takes non-universal values in the non-topological phase. The conductance spectra in the topological state develops a peak at zero bias for certain parameter regimes, with the peak width controlled by the strength of spin-orbit coupling and barrier transparency.

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Section: Introductionmentioning

confidence: 99%

Conductance spectroscopy of topological superconductor wire junctions

Setiawan

Brydon

et al. 2015

Phys. Rev. B

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“…Thus although progress has been reported by using conventional transport and STM experiments [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] , those studies do not have the momentum resolution necessary to distinguish the contribution to the STM or transport signals of the topological surface states from that of the bulk or impurity bands. In fact, it has been recently shown [27][28][29][30] that the undesirable superconductivity in the bulk and impurity bands can lead to ambiguous interpretation of the transport and STM data regarding Majorana fermions. Therefore, in order to realize any of the fascinating theoretical proposals, it is of importance to systematically study the near Fermi level electronic structure in a momentum(band)-resolved manner of the heterostructure sample between a topological insulator and a superconductor, in its proximity induced superconducting regime.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, in order to realize any of the fascinating theoretical proposals, it is of importance to systematically study the near Fermi level electronic structure in a momentum(band)-resolved manner of the heterostructure sample between a topological insulator and a superconductor, in its proximity induced superconducting regime. This is because that without an understanding of the near Fermi level electronic structure in a momentum(band)-resolved manner of a certain TI/SC heterostructure sample, it is not possible to interpret any STM or transport data on that particular sample without any ambiguity due to the bulk or impurity band [27][28][29][30] , and it is further not possible to construct or optimize a TI/SC sample where the superconductivity from the topological surface states dominates and the exciting new physics could be finally realized.…”

Section: Introductionmentioning

confidence: 99%

Fermi-level electronic structure of a topological-insulator/cuprate-superconductor based heterostructure in the superconducting proximity effect regime

Liu

Richardella

et al. 2014

Phys. Rev. B

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We probe the near Fermi level electronic structure of tunable topological insulator (Bi2Se3)-cuprate superconductor Bi2Sr2CaCu2O 8+δ (Tc ≃ 91 K) heterostructures in their proximity induced superconductivity regime. Our careful momentum space imaging provides clear evidence for a twophase coexistence and a striking lack of any strong d-wave proximity effect expected in this system. Our Fermi surface imaging data identifies key contributors in reducing the proximity-induced gap below the 5 meV or to a lower energy range (≪ ∆BSCCO). These results correlate with our observation of momentum space separation between the Bi2Se3 and Bi2Sr2CaCu2O 8+δ Fermi surface topologies and mismatch of lattice symmetries in addition to the presence of a small coherence length. These studies not only provide critical momentum space insights into the Bi2Se3/Bi2Sr2CaCu2O 8+δ heterostructures, but also set an upper bound on the proximity induced gap for realizing much sought out Majorana fermion condition in this system.

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“…Observed MBS signatures, such as a zero-bias tunneling conductance peak, may have other origins [31][32][33][34][35] and should be supplemented by additional measurements [36][37][38][39][40]. However, those signatures do not directly probe non-Abelian statistics [2][3][4]8].…”

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confidence: 99%

Wireless Majorana Bound States: From Magnetic Tunability to Braiding

et al. 2016

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We propose a versatile platform to investigate the existence of Majorana bound states (MBSs) and their nonAbelian statistics through braiding. This implementation combines a two-dimensional electron gas formed in a semiconductor quantum well grown on the surface of an s-wave superconductor, with a nearby array of magnetic tunnel junctions (MTJs). The underlying magnetic textures produced by MTJs provide highly-controllable topological phase transitions to confine and transport MBSs in two dimensions, overcoming the requirement for a network of wires. Obtained scaling relations confirm that various semiconductor quantum well materials are suitable for this proposal. PACS numbers: 74.78.Na,74.25.Ha,74.45.+c In condensed-matter systems Majorana bound states (MBSs) are emergent quasiparticles with exotic non-Abelian statistics and particle-antiparticle symmetry [1][2][3][4][5][6][7]. Elucidating their properties is further motivated by the prospect to use them for fault-tolerant quantum computing [8][9][10]. Typical material systems envisioned for experimental implementations of MBSs include superconducting regions [11] such as those relying on the native p-wave pairing in a vortex core [12], Sr 2 RuO 4 [13,14], and Bechgaard salts [15]. They can also occur with common proximity-induced s-wave pairing when combined with a nontrivial spin structure, which can be provided by spin-orbit coupling (SOC) and magnetic textures [16][17][18][19][20][21][22][23][24] to yield an effective p-wave pairing.Impressive advances in fabricating complex superconducting systems for an unambiguous detection of MBSs remain actively debated [23,[25][26][27][28][29][30]. Observed MBS signatures, such as a zero-bias tunneling conductance peak, may have other origins [31][32][33][34][35] and should be supplemented by additional measurements [36][37][38][39][40]. However, those signatures do not directly probe non-Abelian statistics [2][3][4]8]. While realizing the non-Abelian braiding statistics under exchange would provide both an ultimate proof for the MBS existence and the key element for topological quantum computing, even theoretical schemes imply a significant complexity to implement such braiding [10]. Exchanging vortices on the surface of the p-wave superconductor to close the braiding loop would require an experimental tour de force. Frequently examined one-dimensional (1D) superconductor/semiconductor wire systems avoid the need for challenging vortex manipulation, but that geometry alone is insufficient. Braiding statistics are ill-defined in 1D and complex wire networks must be used instead of single wires, posing additional obstacles [10,41].To address these challenges, in Fig. 1 we propose a versatile platform to realize MBSs and enable their braiding in 2D superconductor/semiconductor systems without the need for wire networks. This proposal seemingly contradicts prior knowledge. In semiconductor wires with SOC-based effective p-wave pairing, the energetically isolated MBSs do not survive the transition to 2D, but rather ev...

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Topologically trivial zero-bias conductance peak in semiconductor Majorana wires from boundary effects

Cited by 93 publications

References 46 publications

Conductance spectroscopy of topological superconductor wire junctions

Conductance spectroscopy of topological superconductor wire junctions

Fermi-level electronic structure of a topological-insulator/cuprate-superconductor based heterostructure in the superconducting proximity effect regime

Wireless Majorana Bound States: From Magnetic Tunability to Braiding

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