VUV Pump and probe of phase separation and oxygen interstitials in La2NiO4+y using spectromicroscopy

TL;DR

This study demonstrates that vacuum ultraviolet (VUV) illumination can manipulate oxygen interstitials and phase separation in La2NiO4+y, revealing a new method to control electronic properties in strongly correlated oxides.

Contribution

It is the first to show VUV light can induce and control oxygen-rich domains and phase separation in La2NiO4+y using spectromicroscopy techniques.

Findings

VUV light increases density of states around 1.4 eV below EF.

Photo-induced states linked to oxygen interstitial clustering.

VUV illumination can generate and manipulate oxygen-rich domains.

Abstract

While it is known that strongly correlated transition metal oxides described by multi-band Hubbard model show microscopic multiscale phase separation little is known on the possibility to manipulate them with vacuum ultraviolet (VUV) 27 eV lighting. We have investigated the photo-induced effects of VUV illumination of a super-oxygenated La2NiO4+y single crystal by means of scanning photoelectron microscopy. VUV light exposure induces the increase of the density of states (DOS) in the binding energy range around Eb =1.4 eV below EF. The photo-induced states in this energy region have been predicted as due to clustering of oxygen interstitials by band structure calculations for large supercell of La2CuO4.125. We finally show that it possible to generate and manipulate oxygen rich domains by VUV illumination as it was reported for X-ray illumination of La2CuO4+y. This phenomenology is assigned to oxygen-interstitials ordering and clustering by photo-illumination forming segregated domains in the La2NiO4+y surface