# Classical and quantum filaments in the ground state of trapped dipolar Bose gases

## TL;DR

This study uses quantum Monte Carlo simulations to explore how dipolar Bose gases transition from classical filamentary structures to quantum fluid states, revealing a smooth evolution influenced by interaction range and quantum effects.

## Contribution

It introduces a detailed analysis of the classical-to-quantum transition in dipolar Bose gases, highlighting the role of interaction range and quantum coherence in filament formation.

## Key findings

- Classical regime features ordered filament arrays dominated by dipolar attraction.
- Quantum regime shows destabilization of filaments leading to a uniform superfluid cloud.
- Intermediate regime exhibits filament structures with quantum phase coherence and superfluidity.

## Abstract

We study by quantum Monte Carlo simulations the ground state of a harmonically confined dipolar Bose gas with aligned dipole moments, and with the inclusion of a repulsive two-body potential of varying range. Two different limits can be clearly identified, namely a classical one in which the attractive part of the dipolar interaction dominates and the system forms an ordered array of parallel filaments, and a quantum-mechanical one, wherein filaments are destabilized by zero-point motion, and eventually the ground state becomes a uniform cloud. The physical character of the system smoothly evolves from classical to quantum mechanical as the range of the repulsive two-body potential increases. An intermediate regime is observed, in which ordered filaments are still present, albeit forming different structures from the ones predicted classically; quantum-mechanical exchanges of indistinguishable particles across different filaments allow phase coherence to be established, underlying a global superfluid response.