Orbital effect of magnetic field on the Majorana phase diagram

Studies of Majorana bound states in semiconducting nanowires frequently neglect the orbital effect of magnetic field. Systematically studying its role leads us to several conclusions for designing Majoranas in this system. Specifically, we show that for experimentally relevant parameter values orbital effect of magnetic field has a stronger impact on the dispersion relation than the Zeeman effect. While Majoranas do not require a presence of only one dispersion subband, we observe that the size of the Majoranas becomes unpractically large, and the band gap unpractically small when more than one subband is filled. Since the orbital effect of magnetic field breaks several symmetries of the Hamiltonian, it leads to the appearance of large regions in parameter space with no band gap whenever the magnetic field is not aligned with the wire axis. The reflection symmetry of the Hamiltonian with respect to the plane perpendicular to the wire axis guarantees that the wire stays gapped in the topologically nontrivial region as long as the field is aligned with the wire.Comment: 5 pages, 6 figures, data available at http://dx.doi.org/10.4121/uuid:20f1c784-1143-4c61-a03d-7a3454914ab

Enhanced proximity effect in zigzag-shaped Majorana Josephson junctions

High density superconductor-semiconductor-superconductor junctions have a small induced superconducting gap due to the quasiparticle trajectories with a large momentum parallel to the junction having a very long flight time. Because a large induced gap protects Majorana modes, these long trajectories constrain Majorana devices to a low electron density. We show that a zigzag-shaped geometry eliminates these trajectories, allowing the robust creation of Majorana states with both the induced gap $E_\textrm{gap}$ and the Majorana size $\xi_\textrm{M}$ improved by more than an order of magnitude for realistic parameters. In addition to the improved robustness of Majoranas, this new zigzag geometry is insensitive to the geometric details and the device tuning.Comment: 5 pages, 4 figure

Conductance Quantization at zero magnetic field in InSb nanowires

Ballistic electron transport is a key requirement for existence of a topological phase transition in proximitized InSb nanowires. However, measurements of quantized conductance as direct evidence of ballistic transport have so far been obscured due to the increased chance of backscattering in one dimensional nanowires. We show that by improving the nanowire-metal interface as well as the dielectric environment we can consistently achieve conductance quantization at zero magnetic field. Additionally, studying the sub-band evolution in a rotating magnetic field reveals an orbital degeneracy between the second and third sub-bands for perpendicular fields above 1T

Exploring CRM effectiveness: an institutional theory perspective

This study identifies the potential contribution that institutional theory can make to understanding the success of marketing practices. Based on institutional theory, we argue that the effectiveness of marketing practices decreases when firms are motivated to adopt such practices under the influence of institutional pressures originating in firms' environments. However, alignment between a practice and a firm's marketing strategy may buffer against these negative effects. We apply these insights to the case of customer relationship management (CRM). CRM is considered an important way to enhance customer loyalty and firm performance, but it has also been criticized for being expensive and for not living up to expectations. Empirical data from 107 organizations confirm that, in general, adopting CRM for mimetic motives is likely to result in fewer customer insights as a result of using this practice. Our study suggests that institutional theory has much to offer to the investigation of the effectiveness of marketing practices

Robustness of Majorana bound states in the short junction limit

Code and resulting data underlying the paper “Robustness of Majorana bound states in the short junction limit”. In this research we have studied the effects of strong coupling between a superconductor and a semiconductor nanowire on the creation of the Majorana bound states, when the quasiparticle dwell time in the normal part of the nanowire is much shorter than the inverse superconducting gap. See CODE_README.md for usage instruction of the code and dat

Designing for friendship: Becoming friends with your ECA

This paper is about the design of Embodied Conversational Agents (ECAs). In this field of Human Computer Interaction (HCI) and Artificial Intelligence (AI), the design of ECAs, or ‘virtual humans’, and the communication between those agents and human users is the main object of our research. A lot of effort is put into research to make ECAs more lifelike and believable and to make communication with ECAs more effective, efficient, and more fun. In order to do so, the idea was to make the agent more actively concerned with the relationship with the user. As a ‘lay psychologist’, we all know that people that you like (or your friends) are able to help you better, teach you better, and generally are more fun to interact with, than people that you don’t like. However, ’liking’ is person dependent. Not everybody likes the same person, and one person is not liked by everyone. These observations sparked our interest in the application, effects, and design of a ‘virtual friend’. An agent that observes it’s user, and adapts it’s personality, appearance and behavior according to the (implicit) likes and dislikes of the user, in order to ‘become friends’ with the user and create an affective interpersonal relationship. This agent might have additional benefits over a ‘normal’ Embodied Conversational Agent in areas such as computer assisted teaching and entertainment

Spin-Orbit Protection of Induced Superconductivity in Majorana Nanowires

International audienceSpin-orbit interaction (SOI) plays a key role in creating Majorana zero modes in semiconductor nanowires proximity coupled to a superconductor. We track the evolution of the induced superconducting gap in InSb nanowires coupled to a NbTiN superconductor in a large range of magnetic field strengths and orientations. Based on realistic simulations of our devices, we reveal SOI with a strength of 0.15-0.35 eV Å. Our approach identifies the direction of the spin-orbit field, which is strongly affected by the superconductor geometry and electrostatic gates