Photoemission spectra of a two-dimensional S=1/2 quantum antiferromagnet in magnetic fields: a theoretical study

TL;DR

This study theoretically investigates how magnetic fields influence the photoemission spectra of a two-dimensional spin-1/2 antiferromagnet, revealing field-dependent quasiparticle behavior and van Hove region changes.

Contribution

It provides a detailed theoretical analysis of ARPES in a 2D quantum antiferromagnet under magnetic fields, highlighting novel field-induced spectral features.

Findings

Quasiparticle bands narrow with increasing magnetic field.

Anomalous extended van Hove region appears near half saturation.

Van Hove regions around (π,0) and (0,π) diminish with field.

Abstract

We calculate the angular resolved photoemission spectra (ARPES) of a spin-1/2 Heisenberg antiferromagnet as a function of magnetic fields using both the exact diagonalization method and self-consistent Born approximation. Below the saturation field $B_C$, strong scattering between spin waves and a hole, created by photoemission of an electron, significantly narrows the quasiparticle band that is characterized by the lowering of the quasiparticle energy at $(\pi,\pi)$ with increasing field. Accordingly, in ARPES the quasiparticle peak gets shaper near $(\pi,\pi)$ and broader elsewhere. Furthermore, we observe that an anomalous extended van Hove region (EVHR) around $(\pi,\pi)$ appears in a half saturation field, while EVHRs around $(\pi,0)$ and $(0,\pi)$ in zero field gradually disappear with increasing field.