Thin Films of Quantum Fluids: History, Phase Transitions, and Wetting

4He monolayer on graphene: a quantum Monte Carlo study

“…The data can be fitted with the expression e(T) = e 0 + αT 3 , yielding e 0 = −129.550(25) K. The first observation is that energy estimates at finite temperature (for T 1 K), for the particular coverage considered here are significantly lower (by about 0.25 K) than the ground state estimate quoted in [20], based on a calculation making use of the same potentials utilized in this work. 1 It is worth noting that the difference between our estimate and that of [20] is three times greater than that between the two results provided in [20], projecting the lowest-energy state out of two initial trial wave functions, one possessing crystalline long-range order and the other not breaking 4 He atom (in K) computed by simulation as a function of the temperature at a coverage θ = 0.0636 Å −2 . Statistical errors are smaller than symbol sizes.…”

“…When not shown, statistical errors are smaller than symbol sizes. 1 For comparison, we have carried out the same calculation with an earlier version of the Aziz helium pair potential [31] and obtained a ∼0.05 K higher ground state energy estimate. No significant change is observed in any of the other physical observables considered in this work if the different helium potential is used.…”

“…The physics of thin helium films varies greatly, depending on the substrate upon which they are adsorbed [1]. The equilibrium phase of 4 He in two dimensions (2D) is a superfluid liquid, and indeed on the weakest substrate for which a stable 2D film forms, namely lithium, a stable superfluid monolayer is predicted [2] and observed [3], with continuous growth of film as a function of the chemical potential [4].…”