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

Abstract

Low dimensional fermionic quantum systems are exceptionally interesting because they reveal distinctive physical phenomena, including among others, topologically protected excitations, edge states, frustration, and fractionalization. Our aim was to confine 3He on a suspended carbon nanotube to form 2-dimensional Fermi-system. Here we report our measurements of the mechanical resonance of the nanotube with adsorbed sub-monolayer down to 10 mK. At intermediate coverages we have observed the famous 1/3 commensurate solid. However, at larger monolayer densities we have observed a quantum phase transition from 1/3 solid to an unknown, soft, and mobile solid phase. We interpret this mobile solid phase as a bosonic commensurate crystal consisting of helium dimers with topologically-induced zero-point vacancies which are delocalized at low temperatures. We thus demonstrate that 3He on a nanotube merges both fermionic and bosonic phenomena, with a quantum phase transition between fermionic solid 1/3 phase and the observed bosonic dimer solid.

Transport of bound quasiparticle states in a two-dimensional boundary superfluid

“…For example, the bound quasiparticles' possible interactions with the sub-gap bosonic excitations or bulk topological defects span at least 7 orders of magnitude in energy below the superfluid gap and some 18 degrees of freedom 32,34 . Our results imply that devising suitable nanoprobes that fit within the two-dimensional superfluid should tap into long-range quasiparticle transport that can be studied in varying topological configurations, such as across different bulk superfluid phases and interfaces, via controlled confinement provided by engineered nanostructures 33,[35][36][37][38][39][40][41] , or across the free surface [42][43][44][45][46][47] . It may also be possible to access these phenomena by engineering the topology of the mechanical probes 48,49 .…”

Phases of He4 and H2 adsorbed on a single carbon nanotube

“…Studying the adsorption capabilities of those carbon cylinders is possible since an isolated carbon nanotube can be synthesized and made to work as a mechanical resonator. Its resonant frequencies change upon loading, allowing in this way an accurate determination of the adsorbate phases [2][3][4][5][6][7][8]. In principle, this resonant frequency can be monitored to check whether we have a supersolid structure, as was done for the second layer of 4 He on graphite [9,10].…”