Prediction for Two Spatially Modulated Superfluids: 
                
                  
                
                $$^4\hbox {He}$$
                
                  
                    
                      
                        
                        4
                      
                      He
                    
                  
                
               on Fluorographene and on Hexagonal BN

Silvestrelli, Pier Luigi; Nava, Marco; Ancilotto, Francesco; Reatto, L.

doi:10.1007/s10909-018-02133-y

Cited by 3 publications

(7 citation statements)

References 36 publications

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“…In the case of 4 He on GF we confirm the main result of the previous studies 7,9 : The ground state of 4 He on GF is a superfluid that has a strong spatial modulation. At variance with the result of 7,9 , we find that at coverage larger than that of the equilibrium state there is a first order phase transition to a commensurate state with triangular symmetry at a coverage corresponding to the occupation of 1/6 of the adsorption sites.…”

Section: Introductionsupporting

confidence: 88%

“…That study was based on a semi empirical adsorption potential. These results have been corroborated by a more recent study 9 in which some of us have developed an adsorption potential based on ab intio methods: even with such adsorption potential it was found that the 4 He atoms on GF are delocalized and the ground state of submonolayer 4 He is a superfluid. Interestingly, that work 9 has shown that also the monolayer of 4 He on hexagonal-Boron Nitride (hBN) turned out to be a superfluid.…”

Section: Introductionmentioning

confidence: 54%

“…How large β has to be must be found empirically in terms of convergence. Our evidence is that the results in [7][8][9] were not fully converged. We are confident that the present VPI results are at convergence also because they are in agreement, as expected, with those of PIMC at low temperature.…”

Section: Introductionmentioning

confidence: 69%

“…2). For GF a nearly isoenergetic configuration is found also above the hollow site 7,9 . Therefore on GF two essentially equivalent kinds of adsorption sites are present and the overall number of adsorption sites is double that on hBN and G. In Table II I.…”

Section: Potentialsmentioning

confidence: 82%

“…Studies of Refs. [7][8][9] are based on state of the art many body computations that should be able to provide exact results for the system. However quantum simulations of particles in a highly structured potential can be tricky due to the multiple energy scales that are present and we decided to perform a new investigation of the adsorption of 4 He atoms on GF, hBN, and G. In the present study we tested the adsorption processes by also adopting an alternative formulation of the ab initio theory.…”

Section: Introductionmentioning

confidence: 99%

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

Moroni,

Ancilotto,

Silvestrelli

et al. 2021

Preprint

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We study a sub monolayer 4 He adsorbed on fluorographene (GF) and on hexagonal boron nitride (hBN) at low coverage. The adsorption potentials have been computed ab-initio with a suitable density functional theory including dispersion forces. The properties of the adsorbed 4 He atoms have been computed at finite temperature with path integral Monte Carlo and at T = 0 K with variational path integral. From both methods we find that the lowest energy state of 4 He on GF is a superfluid. Due to the very large corrugation of the adsorption potential this superfluid has a very strong spatial anisotropy, the ratio between the largest and smallest areal density being about 6, the superfluid fraction at the lowest T is about 55% and the temperature of the transition to the normal state is in the range 0.5-1 K. Thus, GF offers a platform for studying the properties of a strongly interacting highly anisotropic bosonic superfluid. At a larger coverage 4 He has a transition to an 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 and 1 K. The system has a triangular order similar to that of 4 He on graphite but each 4 He atom is not confined to a single adsorption site and the atom visits also the nearest neighboring sites giving rise to a novel three-lobed density distribution. The lowest energy state of 4 He on hBN is an ordered commensurate state with occupation of 1/3 of the adsorption sites and triangular symmetry. A disordered state is present at lower coverage as a metastable state. In presence of an electric field the corrugation of the adsorption potential is slightly increased but up to a magnitude of 1 V/ Å the effect is small and does not change the stability of the phases of 4 He on GF and hBN. We have verified that also in the case of graphene such electric field does not modify the stability of the commensurate √ 3 × √ 3R30 • phase.

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