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

Area of Science:

• Condensed Matter Physics
• Quantum Information Science
• Nanotechnology

Background:

• Quantum wires are crucial for exploring one-dimensional electron and hole transport phenomena.
• Understanding carrier behavior in strained semiconductor heterostructures is key for advanced electronic devices.
• Ballistic transport, where carriers travel without scattering, is essential for high-performance quantum devices.

Purpose of the Study:

• To experimentally investigate ballistic hole transport in gate-defined, one-dimensional (1D) quantum wires within a strained SiGe/Ge/SiGe quantum well.
• To characterize the g-factors and their anisotropy in these 1D systems under magnetic fields.
• To assess the feasibility of long-distance (up to 600 nm) quantized ballistic transport in such structures.

Main Methods:

• Fabrication of gate-defined quantum wires in strained SiGe/Ge/SiGe heterostructures.
• Electrical transport measurements at low temperatures.
• Application of variable magnetic fields (in-plane and out-of-plane) to probe quantum phenomena.
• Analysis of conductance plateaus and Zeeman splitting to determine carrier properties.

Main Results:

• Observation of conductance plateaus at integer multiples of 2 e²/h at zero magnetic field, indicating ballistic transport.
• Significant anisotropy in g-factors, with values <1 in-plane and >10 out-of-plane.
• Confirmation of heavy-hole character of valence-band states due to confinement.
• Demonstration of quantized ballistic conductance in quantum wires up to 600 nm in length.

Conclusions:

• Experimental evidence confirms ballistic hole transport in strained SiGe/Ge/SiGe quantum wires.
• The observed g-factor anisotropy supports the heavy-hole nature of the carriers.
• The ability to maintain quantized ballistic transport over 600 nm is a significant advancement for quantum spintronics applications.