Tuning the quantumness of simple Bose systems: A universal phase diagram

TL;DR

This paper provides a detailed theoretical phase diagram of Bose systems with Lennard-Jones interactions, exploring how quantum effects influence phases from solids to superfluids through first-principles path-integral simulations.

Contribution

It introduces a universal framework for tuning the quantum nature of Bose systems and systematically maps their phase behavior across different regimes using exact numerical methods.

Findings

Phase diagram topology changes with quantum tuning.

Quantum effects significantly alter phase boundaries.

Predictions align with some experimental and mean-field results.

Abstract

We present a comprehensive theoretical study of the phase diagram of a system of many Bose particles interacting with a two-body central potential of the so-called Lennard-Jones form. First-principles path-integral computations are carried out, providing essentially exact numerical results on the thermodynamic properties. The theoretical model used here provides a realistic and remarkably general framework for describing simple Bose systems ranging from crystals to normal fluids to superfluids and gases. The interplay between particle interactions on the one hand, quantum indistinguishability and delocalization on the other, is characterized by a single quantumness parameter, which can be tuned to engineer and explore different regimes. Taking advantage of the rare combination of the versatility of the many-body Hamiltonian and the possibility for exact computations, we systematically investigate the phases of the systems as a function of pressure (P) and temperature (T), as well as the quantumness parameter. We show how the topology of the phase diagram evolves from the known case of He-4, as the system is made more (and less) quantum, and compare our predictions with available results from mean-field theory. Possible realization and observation of the phases and physical regimes predicted here are discussed in various experimental systems, including hypothetical muonic matter.