Ballistic One-Dimensional Holes with Strong g-Factor Anisotropy in Germanium

Abstract

We report experimental evidence of ballistic hole transport in one-dimensional quantum wires gate-defined in a strained SiGe/Ge/SiGe quantum well. At zero magnetic field, we observe conductance plateaus at integer multiples of 2 e/ h. At finite magnetic field, the splitting of these plateaus by Zeeman effect reveals largely anisotropic g-factors with absolute values below 1 in the quantum-well plane, and exceeding 10 out-of-plane. This g-factor anisotropy is consistent with a heavy-hole character of the propagating valence-band states, which is in line with a predominant confinement in the growth direction. Remarkably, we observe quantized ballistic conductance in device channels up to 600 nm long. These findings mark an important step toward the realization of novel devices for applications in quantum spintronics.

Physics of arbitrarily doped Kondo lattices: From a commensurate insulator to a heavy Luttinger liquid and a protected helical metal

“…However, modern solid-state technology also allows one to engineer specific 1D KL even in solid state platforms. It looks feasible to fabricate 1D KL in clean 1D quantum wires made, e.g., in GaAs/AlGaAs by using cleaved edge overgrowth technique [67] or in SiGe [68]. Magnetic adatoms can be deposited close to the quantum wire with the help of the precise ion beam irradiation.…”

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

“…In analogy to electron spin qubits in Si/SiGe, to fabricate gated Ge quantum devices it is preferable to completely eliminate dopant atoms from the Ge/SiGe heterostructure. Indeed, gate controlled quantum dots, ballistic 1D channels, and ballistic phase coherent superconductivity were demonstrated recently by using undoped Ge/SiGe. So far the added complexity in developing reliable gate‐stacks has limited the investigation of quantum transport properties in undoped Ge/SiGe to devices with mobilities significantly inferior compared to modulation‐doped structures …”

Germanium Quantum-Well Josephson Field-Effect Transistors and Interferometers

“…Those based on p-type SiGe heterostructures are readily compatible with silicon technology, 24 and, thanks to their intrinsically strong spin-orbit coupling, they are an attractive candidate for the development of topological superconducting systems. 22,[25][26][27][28][29][30][31][32] In this work, we present proof-of-concept S-Sm devices in which the semiconducting element consists of an undoped SiGe heterostucture embedding a strained Ge quantum-well (QW). A high-mobility two-dimensional hole gas (2DHG) is electrostatically accumulated in the QW by means of a surface gate electrode.…”