Topologically-imposed vacancies and mobile solid ³He on carbon nanotube

Area of Science:

• Low-dimensional quantum physics
• Condensed matter physics
• Materials science

Background:

• Low-dimensional fermionic systems exhibit unique phenomena like topological protection and fractionalization.
• Confining quantum systems allows for the study of emergent behaviors and phase transitions.

Purpose of the Study:

• To confine Helium-3 (³He) on a suspended carbon nanotube to create a 2D Fermi system.
• To investigate the mechanical resonance of the nanotube with adsorbed ³He at millikelvin temperatures.
• To explore quantum phase transitions in this confined system.

Main Methods:

• Measurements of nanotube mechanical resonance with adsorbed ³He.
• Experiments conducted at temperatures as low as 10 mK.
• Analysis of ³He behavior at various sub-monolayer coverages.

Main Results:

• Observed the 1/3 commensurate solid phase of ³He at intermediate coverages.
• Discovered a quantum phase transition at higher densities.
• Identified a novel, soft, and mobile solid phase interpreted as a bosonic commensurate crystal of helium dimers with delocalized zero-point vacancies.

Conclusions:

• Demonstrated that ³He on a carbon nanotube exhibits both fermionic and bosonic phenomena.
• Showcased a quantum phase transition between a fermionic solid and a bosonic dimer solid.
• Highlighted the role of topological phenomena and zero-point vacancies in the observed bosonic phase.