Supercooled superfluids in Monte Carlo simulations

Abstract

Abstract. We perform path integral Monte Carlo simulations to study the imaginary time dynamics of metastable supercooled superfluid states and nearly superglassy states of a one component fluid of spinless bosons square wells. Our study shows that the identity of the particles and the exchange symmetry is crucial for the frustration necessary to obtain metastable states in the quantum regime. Whereas the simulation time has to be chosen to determine whether we are in a metastable state or not, the imaginary time dynamics tells us if we are or not close to an arrested glassy state.Key words. Square-well bosons -hard-spheres -supercooled liquid -superfluid -glass -superglassmode-coupling-theory -path-integral Monte Carlo -worm algorithm.PACS. 61.20. .PIf a liquid can be cooled below its melting temperature T m without the occurrence of crystallization, it is called a good glass former, and when the temperature is less than T m the system is called supercooled. The static and dynamical properties of such systems can be studied over a large temperature range below T m and it is found that their relaxation times increase very quickly by many decades if the temperature is lowered. At a certain temperature the relaxation time exceeds the timescale of the experiment and therefore the system will fall out of equilibrium. It is this falling out of equilibrium that is called the glass transition. At temperatures well below this glass transition temperature no relaxation seems to take place any longer, on any reasonable timescale, and it is customary to call this material a glass. This transition temperature will in general depend on the type of experiment, since its definition involves the timescale of the experiment. Understanding the transition from a supercooled liquid to a glass, or a disordered solid, is one of the major open problems in condensed matter.In a liquid of number density ρ, made of mass m particles, moving in a d−dimensional space, the quantum effects will become important when the temperature T is comparable or smaller than the degeneracy temperature2/d , where λ = 2 /2m and is the reduced Planck constant. A liquid such that T D > T m is therefore likely to form a quantum glass.At a temperature T MCT < T m a kinetic glass transition towards an arrested state is predicted by the Mode Coupling Theory (MCT) [1,2]. Many of the qualitative predictions of this theory have been confirmed in experiments and computer simulations, and thus MCT can currently a e-mail: rfantoni@ts.infn.it be regarded as the best available theory of the dynamics of supercooled liquids.Our aim in this letter is to use Path Integral Monte Carlo (PIMC) simulations [3] to gain an understanding on the very general question of the search for an arrested state when the temperature approaches T MCT . Since we are interested in an universal property of glassy systems, our simulations are carried out with a very simple and unrealistic model liquid, namely the square-well bosons [4]. We will be working at very low Temperatures T ≈ T m < T D . ...

Jellium at finite temperature

“…Our algorithm briefly presented in the previous section is based on the worm algorithm of Boninsegni et al [39,56,[59][60][61]. This algorithm uses a menu of 9 moves.…”

Jellium at finite temperature using the restricted worm algorithm

“…Our algorithm, that we will call algorithm A, briefly presented in the previous section is based on the worm algorithm of Boninsegni et al 33,52,[55][56][57] . The algorithm of Boninsegni et al solves the path integral in the grand canonical ensemble and uses a menu of 9 moves.…”

Quantum crystallography of Rydberg-dressed Bose gases on a square lattice

“…As a supersoild may be observable in experiments with Rydberg-dressed alkali atoms, other quantum crystallographic states, such as superglass, are expected to be established. The superglass corresponding to a matter state that simultaneously possesses superfluidity and a frozen amorphous structure [31][32][33][34][35][36][37][38][39].…”