English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We study a sub monolayer He-4 adsorbed on fluorographene (GF) and onhexagonal boron nitride (hBN) at low coverage. The adsorption potentials havebeen computed ab-initio with a suitable density functional theory includingdispersion forces. The properties of the adsorbed He-4 atoms have been computedat finite temperature with path integral Monte Carlo and at T=0 K withvariational path integral. From both methods we find that the lowest energystate of He-4 on GF is a superfluid. Due to the very large corrugation of theadsorption potential this superfluid has a very strong spatial anisotropy, theratio between the largest and smallest areal density being about 6, thesuperfluid fraction at the lowest T is about 55%, and the temperature of thetransition to the normal state is in the range 0.5-1 K. Thus, GF offers aplatform for studying the properties of a strongly interacting highlyanisotropic bosonic superfluid. At a larger coverage He-4 has a transition toan ordered commensurate state with occupation of 1/6 of the adsorption sites.This phase is stable up to a transition temperature located between 0.5 and1~K. The system has a triangular order similar to that of He-4 on graphite. Thelowest energy state of He-4 on hBN is an ordered commensurate state withoccupation of 1/3 of the adsorption sites and triangular symmetry. A disorderedstate is present at lower coverage as a metastable state. In the presence of anelectric field the corrugation of the adsorption potential is slightlyincreased but up to a magnitude of 1 V/Ang. the effect is small and does notchange the stability of the phases of He-4 on GF and hBN. We have verified thatalso in the case of graphene such electric field does not modify the stabilityof the commensurate sqrt{3}*sqrt{3}R30 phase.

Localization versus inhomogeneous superfluidity: Submonolayer He-4 on fluorographene, hexagonal boron nitride, and graphene