Naslov
Superfluidity, BEC, and dimensions of liquid He4 in nanopores

Autori
Vranješ Markić, Leandra ; Glyde, Henry R.

Izvornik
Physical Review B - Condensed Matter and Materials Physics (1098-0121) 92 (2015); 064510-1

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
helium; superfluidity; Bose-Einstein condensation; disorder; nanopore; BEC; Path Integral Monte Carlo; liquid 4He; nanopore

Sažetak
We present path integral Monte Carlo (PIMC) calculations of the superfluid fraction, ρS/ρ, and the one-body density matrix (OBDM) [Bose- Einstein condensation (BEC)] of liquid He4 confined in nanopores. Liquid He4 in nanopores represents a dense Bose liquid at reduced dimension and in disorder. The goal is to determine the effective dimensions of the liquid in the pores. It is to test whether observed properties, such as a very low onset temperature for superflow, Tc, can be predicted by a standard, static PIMC ρS/ρ. We simulate a cylinder of liquid of diameter dL surrounded by 5 Å of inert solid He4 in a nanopore of diameter d ; d=dL+10Å. We find a PIMC ρS(T)/ρ and OBDM that scales as a 1D fluid Luttinger liquid at extremely small liquid pore diameters only, dL=6Å. At this dL, the liquid fills the pore in a 1D line at the center of the pore and there is no PIMC superflow. In the range 8≤dL≤22Å the PIMC ρS(T)/ρ scales as a 2D liquid. In this dL range the liquid fills the pores in 2D-like cylindrical layers. The crossover from no superflow at d=16Å to superflow at d≥18Å agrees with experiment. There is a crossover to 3D scaling at larger dL≃22Å. In the range 8≤dL≤22Å, the Tc predicted using the Kosterlitz-Thouless 2D scaling criterion of the OBDM agrees well with that obtained from ρS(T)/ρ. These results suggest that the superflow observed in small pore media is standard static superflow with the low Tc arising from its 2D character. An operational onset temperature, TBEC, for BEC can be defined as the temperature at which there is a crossover from exponential to algebraic decay in the OBDM. This definition leads to a TBEC≥Tc as observed in larger pore media.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

Napomena
Rad je kao poster prezentiran na skupovima: International Symposium on Quantum Fluids and Solids, održanom od 09.-15.08.2015.g., i XVIIIth International Conference on Recent Progress in Many-Body Theories, održanom od 16.-21.08.2015.g., Niagara Falls, SAD ; objavljen u Knjizi sažetaka ; 2015.g.

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