Energy gaps and roton structure above the nu=1/2 Laughlin state of a rotating dilute Bose-Einstein condensate

TL;DR

This study uses exact diagonalization to explore how vortex entry affects the energy spectrum of a rotating dilute Bose-Einstein condensate, revealing energy gaps and roton-like features above the nu=1/2 Laughlin state.

Contribution

It uncovers the evolution of energy gaps and roton structures in the spectrum as vortices enter, highlighting novel spectral features in rotating BECs.

Findings

Energy gap appears with the first vortex entry.

Energy gap decreases with more vortices but remains non-zero.

Roton-like spectrum emerges without a phonon branch.

Abstract

Exact diagonalization study of a rotating dilute Bose-Einstein condensate reveals that as the first vortex enters the system the degeneracy of the low-energy yrast spectrum is lifted and a large energy gap emerges. As more vortices enter with faster rotation, the energy gap decreases towards zero, but eventually the spectrum exhibits a rotonlike structure above the nu=1/2 Laughlin state without having a phonon branch despite the short-range nature of the interaction.