Electronic Bound States in the Continuum in a 2D Metal

TL;DR

This paper reports the experimental observation of electronic bound states in the continuum within a 2D metallic system, demonstrating localized states that coexist with delocalized metallic states due to interference effects.

Contribution

First demonstration of electronic BICs in a 2D metal, revealing how lattice interference can produce localized states within a metallic continuum.

Findings

Localized defect states observed in Pd5AlI2

Interference causes flat bands and localization

States remain orthogonal to the metallic continuum

Abstract

Bound states in the continuum (BICs) are quantum states that remain localized despite existing within a continuum of extended, delocalized states. They defy conventional wave theories and could be instrumental for quantum technologies that rely on the precise control of quantum states. While optical BICs have been realized in photonic systems, achieving electronic bound states in a metallic background remains an ongoing challenge. Here, we observe two defect states that remain localized within the metallic continuum of Pd5AlI2, a two-dimensional van der Waals metal. The emergence of these states is a manifestation of the hopping interference in the Pd5AlI2 lattice. This interference results in a (quasi) flat band and spatially localized eigenstates that are orthogonal to the metallic continuum thus avoiding hybridization with extended states.