Low energy excitations in A-site ordered SmBaMn2O6

TL;DR

This study uses advanced x-ray scattering techniques to investigate low-energy excitations related to orbital order in SmBaMn₂O₆, revealing potential orbital excitations below 200 meV with temperature-dependent behavior.

Contribution

The paper demonstrates the use of high-resolution RIXS and REXS to identify and analyze orbital excitations in a specific manganite compound, advancing understanding of orbital order origins.

Findings

Confirmed orbital order at q = (0.25, 0.25, 0) in SmBaMn₂O₆.

Identified low-energy excitations below 200 meV with some showing temperature dependence linked to orbital order.

Distinguished excitations of magnetic, phononic, and orbital origins.

Abstract

The electron in a solid can be considered a bound state of the three independent, fundamental degrees of freedom creating quasi-particles: spinons, carrying the electron spin; plasmons carrying the collective charge mode and orbitons carrying its orbital degree of freedom. These fundamental degrees of freedom could form ordering states in which dynamics or collective motions could occurr and manifest as low-energy excitations. The exotic properties that appear in the materials exhibiting these electronic orderings are associated with these low-energy excitations. Although the orbital order (OO) and its coupling to the spin system creates very interesting phenomena, the microscopic origin of OO has been much less explored than other electronic properties as it is very difficult to directly access experimental information from OO. Due to the recent improvement in energy resolution and flux, soft x-ray resonant inelastic scattering (RIXS) allows for a re-examination of orbital excitations in manganites. Here, we present a study of low energy excitations in half doped A-site ordered SmBaMn_{2}O_{6} through a combination of RIXS and soft x-ray resonant elastic scattering (REXS) measurements. The obtained experimental data confirm the OO at \mathbf{q} = (0.25, 0.25, 0) and find various low energy excitations below 200 meV. while several excitations can be assigned to be of magnetic and phononic origin, a group of excitations between 80 and 200 meV show a temperature dependence distinctively following that of the OO making them possible candidates for orbital excitations.