Excitations of Few-Boson Systems in 1-D Harmonic and Double Wells

TL;DR

This paper investigates the excitation spectrum of few-boson systems in one-dimensional harmonic and double-well traps, revealing how interactions and potential shape influence energy levels and state evolution through fermionization.

Contribution

It provides a detailed, numerically exact analysis of excitation spectra and state evolution in 1D bosonic systems across different trapping potentials and interaction regimes.

Findings

Interaction causes level splitting and merging in harmonic traps.

Fermionization rearranges the low-lying spectrum in double wells.

Level adhesion and crossings are observed during fermionization.

Abstract

We examine the lowest excitations of one-dimensional few-boson systems trapped in double wells of variable barrier height. Based on a numerically exact multi-configurational method, we follow the whole pathway from the non-interacting to the fermionization limit. It is shown how, in a purely harmonic trap, the initially equidistant, degenerate levels are split up due to interactions, but merge again for strong enough coupling. In a double well, the low-lying spectrum is largely rearranged in the course of fermionization, exhibiting level adhesion and (anti-)crossings. The evolution of the underlying states is explained in analogy to the ground-state behavior. Our discussion is complemented by illuminating the crossover from a single to a double well.