Topological suppression of magnetoconductance oscillations in NS junctions

We show that the magnetoconductance oscillations of laterally-confined 2D NS junctions are completely suppressed when the superconductor side enters a topological phase. This suppression can be attributed to the modification of the vortex structure of local currents at the junction caused by the topological transition of the superconductor. The two regimes (with and without oscillations) could be seen in a semiconductor 2D junction with a cleaved-edge geometry, one of the junction arms having proximitized superconductivity. We predict similar oscillations and suppression as a function of the Rashba coupling. The oscillation suppression is robust against differences in chemical potential and phases of lateral superconductors.Comment: 7 pages, 7 figure

Majorana states and magnetic orbital motion in planar hybrid nanowires

The Majorana phase boundaries in planar 2D hybrid (semiconductor-superconductor) nanowires are modified by orbital effects due to off plane magnetic components. We show that Majorana zero modes survive sizable vertical field tiltings, uncovering a remarkable phase diagram. Analytical expressions of the phase boundaries are given for the strong orbital limit. These phase boundaries can be fulfilled with attainable setups, such as an InAs nanowire of $150\, {\rm nm}$ in transverse width.Comment: 9 pages, 6 figures. ( Only acknowledgement update

Electromagnetic absorption of quasi-1D Majorana nanowires

We calculate the electromagnetic absorption cross section of long and narrow nanowires, in the so-called quasi-1D limit. We consider only two transverse bands and compute the dipole absorption cross section taking into account quasiparticle transitions from negative to positive energy eigenstates of the Bogoliubov-de Gennes Hamiltonian. The presence of the zero energy (Majorana) state manifests in the different absorption spectra for $x$ (parallel) and $y$ (transverse) polarizations of the electromagnetic field. In the $y$-polarized case, the Majorana state causes a low energy absorption plateau extending from mid-gap up to full-gap energy. Increasing further the energy, the plateau is followed by a region of enhanced absorption due to transitions across the full gap. For $x$ polarization the low energy absorption plateau is not observed.Comment: Submitted to E-MRS Spring Meeting 2015 ( Only acknowledgement update

Conductance oscillations and speed of chiral Majorana mode in a quantum-anomalous-Hall 2d strip

We predict conductance oscillations in a quantum-anomalous Hall 2d strip having a superconducting region of length $L_x$ with a chiral Majorana mode. These oscillations require a finite transverse extension of the strip $L_y$ of a few microns or less. Measuring the conductance periodicity with $L_x$ and a fixed bias, or with bias and a fixed $L_x$, yields the speed of the chiral Majorana mode. The physical mechanism behind the oscillations is the interference between backscattered chiral modes from second to first interface of the NSN double junction. The interferometer effect is enhanced by the presence of side barriers.Comment: 9 pages, 9 figures. Added references. Added Supplemental Material results. Published versio

Zoning and the Law of Nuisance

We calculate density and current spatial distributions of a 2D model junction between a normal QAH contact and a superconducting QAH region hosting propagating (chiral) Majorana modes. We use a simplified Hamiltonian describing the spatial coupling of the modes on each side of the junction, as well as the related junction conductance. We study how this coupling is affected by orbital effects caused by an external magnetic field.This work was funded by MINEICO-Spain, grant MAT2017-82639

Effects of tilting the magnetic field in 1D Majorana nanowires

We investigate the effects that a tilting of the magnetic field from the parallel direction has on the states of a 1D Majorana nanowire. Particularly, we focus on the conditions for the existence of Majorana zero modes, uncovering an analytical relation (the sine rule) between the field orientation relative to the wire, its magnitude and the superconducting parameter of the material. The study is then extended to junctions of nanowires, treated as magnetically inhomogeneous straight nanowires composed of two homogeneous arms. It is shown that their spectrum can be explained in terms of the spectra of two independent arms. Finally, we investigate how the localization of the Majorana mode is transferred from the magnetic interface at the corner of the junction to the end of the nanowire when increasing the arm length.Comment: 10 pages, 13 figures. ( Only acknowledgement update

Implementation of a Stochastic Optical Quantum Circuit Simulator ( SOQCS )

We present Stochastic Optical Quantum Circuit Simulator (SOQCS) C++/Python library for the simulation of quantum optical circuits, and we provide its implementation details. SOQCS offers a framework to define, simulate and study quantum linear optical circuits in the presence of various imperfections. These come from partial distinguishability of photons, lossy propagation media, unbalanced beamsplitters and non-ideal emitters and detectors for example. SOQCS is developed as a series of different modules which provide quantum circuits, different simulator cores and tools to analyze the output. Quantum circuits can be defined from basic components, including emitters, linear optical elements, delays and detectors. Post-selection can be configured straightforwardly as part of detector definitions. An important attribute of SOQCS is its modularity which allows for its further development in the future.Comment: 25 pages, 10 figure