On controlling the bound states in quantum-dot hybrid-nanowire

TL;DR

This paper models quantum-dot--nanowire systems to understand and control zero-energy bound states, including their emergence from Andreev states and interaction with Majorana states, aiding experimental nanodevice development.

Contribution

It provides a microscopic Bogoliubov--de Gennes model to reproduce experimental observations and analyze control mechanisms of bound states in quantum-dot--nanowire structures.

Findings

Zero-energy bound states can emerge from Andreev states in trivial phase.

Control of bound states is achievable via magnetic and electrostatic means.

Resonance between zero-energy states and Majorana states can occur in non-trivial phase.

Abstract

Recent experiments using the quantum dot coupled to the topological superconducting nanowire [M.T. Deng et al., Science 354, 1557 (2016)}] revealed that zero-energy bound state coalesces from the Andreev bound states. Such quasiparticle states, present in the quantum dot, can be controlled by the magnetic and electrostatic means. We use microscopic model of the quantum-dot--nanowire structure to reproduce the experimental results, applying the Bogoliubov--de~Gennes technique. This is done by studying the gate voltage dependence of the various types of bound states and mutual influence between them. We show that the zero energy bound states can emerge from the Andreev bound states in topologically trivial phase and can be controlled using various means. In non-trivial topological phase we show the possible resonance between this zero energy levels with Majorana bound states. We discuss and explain this phenomena as a result of dominant spin character of discussed bound states. Presented results can be applied in experimental studies by using the proposed nanodevice.