Creation and manipulation of bound states in continuum with lasers: Applications to cold atoms and molecules

TL;DR

This paper theoretically demonstrates how to create and control bound states in continuum in ultracold atoms using lasers and Feshbach resonances, enabling new spectroscopic and molecular formation techniques.

Contribution

It introduces a method to generate and manipulate bound states in continuum in cold atoms via laser-induced superpositions, with potential applications in ultracold molecule creation.

Findings

Bound states in continuum can be formed in ultracold atoms using lasers.

Such states are decoupled from collisional continua and are non-decaying.

Distinct spectral signatures indicate the presence of BICs.

Abstract

We show theoretically that it is possible to create and manipulate a pair of bound states in continuum in ultracold atoms by two lasers in the presence of a magnetically tunable Feshbach resonance. These bound states are formed due to coherent superposition of two electronically excited molecular bound states and a quasi-bound state in ground-state potential. These superposition states are decoupled from the continuum of two-atom collisional states. Hence, in the absence of other damping processes they are non-decaying. We analyze in detail the physical conditions that can lead to the formation of such states in cold collisions between atoms, and discuss the possible experimental signatures of such states. An extremely narrow and asymmetric shape with a distinct minimum of photoassociative absorption spectrum or scattering cross section as a function of collision energy will indicate the occurrence of a bound state in continuum (BIC). We prove that the minimum will occur at an energy at which the BIC is formed. We discuss how a BIC will be useful for efficient creation of Feshbach molecules and manipulation of cold collisions. Experimental realizations of BIC will pave the way for a new kind of bound-bound spectroscopy in ultracold atoms.