Chiral bound states in the continuum

TL;DR

This paper introduces a new mechanism for bound states in the continuum in chiral quantum systems, highlighting their formation, algebraic characterization, and potential experimental realizations.

Contribution

It presents a novel mechanism for BICs in chiral systems, with algebraic rules for their count and analysis of transport properties and experimental setups.

Findings

Zero-energy states exist only in one subsystem due to chiral symmetry.

Some of these states remain bound when coupled to a continuum.

Fano resonances appear in transport measurements.

Abstract

We present a distinct mechanism for the formation of bound states in the continuum (BICs). In chiral quantum systems there appear zero-energy states in which the wave function has finite amplitude only in one of the subsystems defined by the chiral symmetry. When the system is coupled to leads with a continuum energy band, part of these states remain bound. We derive some algebraic rules for the number of these states depending on the dimensionality and rank of the total Hamiltonian. We examine the transport properties of such systems including the appearance of Fano resonances in some limiting cases. Finally, we discuss experimental setups based on microwave dielectric resonators and atoms in optical lattices where these predictions can be tested.