Majorana zero modes in gate-defined germanium hole nanowires

Abstract

We theoretically study gate-defined one-dimensional channels in planar Ge hole gases as a potential platform for non-Abelian Majorana zero modes. We model the valence band holes in the Ge channel by adding appropriate confinement potentials to the 3D Luttinger-Kohn Hamiltonian, additionally taking into account a magnetic field applied parallel to the channel, an out-of-plane electric field, as well as the effect of compressive strain in the parent quantum well. Assuming that the Ge channel is proximitized by an $s$-wave superconductor (such as, e.g., Al) we calculate the topological phase diagrams for different channel geometries, showing that sufficiently narrow Ge hole channels can indeed enter a topological superconducting phase with Majorana zero modes at the channel ends. We estimate the size of the topological gap and its dependence on various system parameters such as channel width, strain, and the applied out-of-plane electric field, allowing us to critically discuss under which conditions Ge hole channels may manifest Majorana zero modes. Since ultra-clean Ge quantum wells with hole mobilities exceeding one million and mean-free paths on the order of many microns already exist, gate-defined Ge hole channels may be able to overcome some of the problems caused by the presence of substantial disorder in more conventional Majorana platforms.

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• Progress in superconductor-semiconductor topological Josephson junctions
• Phenomenology of Majorana zero modes in full-shell hybrid nanowires
• Microscopic analysis of proximity-induced superconductivity and metallization effects in superconductor-germanium hole nanowires
• Nonlocality of local Andreev conductances as a probe for topological Majorana wires
• Germanium-based hybrid semiconductor-superconductor topological quantum computing platforms: Disorder effects
• InP/GaSb core-shell nanowires: a novel hole-based platform with strong spin-orbit coupling for full-shell hybrid devices
• Superconducting Proximity Effect in Two-Dimensional Hole Gases
• Hole subband dispersions and strong `spin'-orbit coupling in a cylindrical Ge nanowire
• Supercurrent and multiple Andreev reflections in Ge hut nanowire Josephson Junctions
• Ballistic transport in 1D Rashba systems in the context of Majorana nanowires
• One-dimensional topology and topolectrics of nonsymmorphic Kramers degenerate systems
• Current cross-correlation spectroscopy of Majorana bound states
• Rashba spin-orbit coupling and artificially engineered topological superconductors