Photoemission study of (V$_{1-x}$M$_x$)$_2$O$_3$ (M=Cr, Ti)

TL;DR

This study uses high-resolution photoemission spectroscopy to analyze the electronic structure of (V$_{1-x}$M$_x$)$_2$O$_3$ across different phases and doping levels, revealing discrepancies with theoretical predictions and phase-dependent spectral changes.

Contribution

It provides detailed experimental spectra of doped vanadium oxide across multiple phases, highlighting differences from theoretical models and the effects of doping on electronic gaps.

Findings

Quasiparticle peak in the PM phase aligns with LDA+DMFT theory but is broader and more intense.

Spectral structures in PI and AFI phases are complex and not fully understood theoretically.

Doping alters the energy gaps and spectral weight distribution in a phase-dependent manner.

Abstract

We present high-resolution bulk-sensitive photoemission spectra of (V$_{1-x}$M$_x$)$_2$O$_3$ (M=Cr, Ti). The measurements were made for the paramagnetic metal (PM), paramagnetic insulator (PI), and antiferromagnetic insulator (AFI) phases of (V$_{1-x}$M$_x$)$_2$O$_3$ with the samples of $x$ = 0, 0.012, and 0.028 for Cr-doping and $x$ = 0.01 for Ti-doping. In the PM phase, we observe a prominent quasiparticle peak in general agreement with theory, which combines dynamical mean-field theory with the local density approximation (LDA+DMFT). The quasiparticle peak shows a significantly larger peak width and weight than in the theory. For both the PI and AFI phases, the vanadium 3d parts of the valence spectra are not simple one peak structures. For the PI phase, there is not yet a good theoretical understanding of these structures. The size of the electron removal gap increases, and spectral weight accumulates in the energy range closer to the chemical potential, when the PI to AFI transition occurs. Spectra taken in the same phases with different compositions show interesting monotonic changes as the dopant concentration increases, regardless of the dopant species. With increased Cr-doping, the AFI phase gap decreases and the PI phase gap increases.