Helical Hole State in Multiple Conduction Modes in Ge/Si Core/Shell Nanowire

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Helical states are crucial for realizing Majorana zero modes in solid-state systems.
• Previous reports of helical states were primarily in the conduction band of III-V nanowires (NWs) with strong Rashba spin-orbit interaction.

Purpose of the Study:

• To report the observation of helical hole states in a Ge/Si core/shell NW system.
• To explore the potential advantages of Ge/Si NWs for spintronic applications and Majorana zero mode engineering.

Main Methods:

• Magneto-transport measurements were performed on Ge/Si core/shell NWs.
• Analysis of re-entrant conductance features to identify helical states.
• Weak antilocalization measurements were used for comparison.

Main Results:

• Observed re-entrant conductance features indicative of helical hole states in multiple conduction modes.
• Derived a Landé g factor of 3.6, consistent with theoretical predictions and larger than in quantum dots.
• Evaluated the spin-orbit energy to be approximately 2.1 meV, comparable to III-V NWs.

Conclusions:

• The Ge/Si core/shell NW system hosts helical hole states, demonstrating its potential for Majorana zero mode engineering.
• Ge/Si NWs offer advantages like longer spin coherence times and suitability for nuclear spin-free devices.
• The findings align with theoretical predictions and experimental observations in other systems, validating the Ge/Si platform.