Quantum point contact as a probe of a topological superconductor

Abstract

We calculate the conductance of a ballistic point contact to a superconducting wire, produced by the s-wave proximity effect in a semiconductor with spin-orbit coupling in a parallel magnetic field. The conductance G as a function of contact width or Fermi energy shows plateaus at halfinteger multiples of 4e 2 /h if the superconductor is in a topologically nontrivial phase. In contrast, the plateaus are at the usual integer multiples in the topologically trivial phase. Disorder destroys all plateaus except the first, which remains precisely quantized, consistent with previous results for a tunnel contact. The advantage of a ballistic contact over a tunnel contact as a probe of the topological phase is the strongly reduced sensitivity to finite voltage or temperature.PACS numbers: 73.23. Ad, 74.25.fc, 74.45.+c II. INTEGER VERSUS HALF-INTEGER CONDUCTANCE PLATEAUSWe consider the model Hamiltonian [14,15] of a two-dimensional semiconducting wire with an s-wave proximity-induced superconducting gap ∆. (See App. A for a detailed description.) We have calculated the

Enhanced Zero-Bias Majorana Peak in the Differential Tunneling Conductance of Disordered Multisubband Quantum-Wire/Superconductor Junctions

“…The intentional inclusion of disorder in or near the barrier, either during the fabrication process of the InSb nanowires used in the experiment, or after fabrication of the device, could thus lead to an additional, strong signature of the Majorana end state. A similar effect is expected if the tunnel barrier is replaced by a point contact [11], provided the point contact is non-adiabatic.…”

Majorana fermion induced nonlocal current correlations in spin-orbit coupled superconducting wires

“…These ZBCPs were possibly due to the MF induced Andreev reflections. 16,17 However, the origin of these ZBCPs remains a subject of debate. [18][19][20][21][22][23][24][25] In this work, instead of studying MF induced local Andreev reflections, [18][19][20][21][22][23][24][25] we explore the nonlocal properties of MFs.…”

Manipulating Majorana fermions using supercurrents

“…While initial proposals examined simple mean-field models of clean wires proximate to a superconductor, more recent work indicates that the induced topological phase persists in the presence of moderate interactions [22][23][24] or disorder, [25][26][27][28][29] and considered setups for probing the Majorana bound states. 11,[30][31][32][33] Experimental challenges nevertheless remain: realizing the topological phase requires control over the wire's global electron density and the application of significant Zeeman fields without destroying superconductivity. Furthermore, manipulating Majorana fermions by locally controlling the electron density using gate electrodes 16,21,34 is nontrivial due to strong screening by the superconductor.…”