Excitations near the boundary between a metal and a Mott insulator

TL;DR

This paper investigates the boundary excitations in a heterostructure of a metal and a Mott insulator, revealing localized spin-wave modes and induced antiferromagnetic order in the metal near the interface.

Contribution

It provides a detailed analysis of boundary excitations and magnetic ordering in a metal-Mott insulator heterostructure with identical lattice parameters.

Findings

Localized spin-wave mode near the interface with two-dimensional dispersion

Induced antiferromagnetic order in the metal decaying exponentially

Boundary mode ejects bulk modes from the interface region

Abstract

A heterostructure of a semi-infinite metal and a Mott insulator is considered. It is supposed that both materials have an identical lattice spacing and hopping integrals and differ in the Hubbard repulsion which is negligible in the metal and exceeds the critical value for the Mott transition in the insulator. At half-filling and for low temperatures the insulator has the long-range antiferromagnetic order. Its low-lying elementary excitations are standing spin waves and a spin-wave mode which is localized near the interface and has a two-dimensional dispersion. This mode ejects bulk modes from the boundary region. The antiferromagnetic ordering of the insulator induces an antiferromagnetic order in the metal where the magnetization decays exponentially with distance from the interface. This decay is characterized by the correlation length equal to 5-6 lattice spacings.