Experimental and Theoretical Investigation of the Pre-Peaks at the Ti K -Edge Absorption Spectra in TiO ₂

Abstract

The available calculated density of states of TiOz does not predict the very first weak peak at the onset of the Ti K-edge absorption spectra indicating that this feature is not simply due to a one-electron (dipole) transition. In this short paper we present a joint experimental and theoretical study of all the three weak pre-peaks at the Ti K-edge of Ti02. Our interpretation takes into account both dipole and quadrupole transitions as well as the influence of the core hole effect.

Polarization dependence of the V K edge in VO2 through the phase transition at 68 °C

“…Now, about the number of pcaks, we have shown before that there are actually three [8] but the intensity of the one in the middle is much greater than the others. This observation has found an explication in [15].…”

“…It has been demonstrated in previous papers that the pre-edge intensity is determined by several parameters: the quadrupole cross section (weak, [8,15]), a dipolar cross section arising from a solid state effect [15], a temperature relaxation [16], and the local symmetry [17, 181. In the present study, the last point is expected to be the predominant effect as the local symmetry is reduced from D,, to approximately C, (Fig. 1).…”

Hard X-ray resonant electronic spectroscopy in transition metal oxides

“…Previous studies used polarizationdependent X-ray absorption to elucidate the origin of these structures. The experimental results [10,16], as well as theoretical calculations [10,11], show that A 1 is due to quadrupolar transitions (1s-3d) while A 2 is mainly due to dipolar transitions (1s-np). Nevertheless, a weak polarization dependence shows a small QT contribution to the A 2 pre-peak.…”

“…Many K-edges of 3d element oxides exhibit weak pre-peaks which have been extensively studied both experimentally and theoretically [9][10][11][12]. These pre-peaks arise from excitations into p and/or d orbitals, and consequently, involve both dipolar and quadrupolar transitions (QT).…”

Proposal for detecting spin-chirality terms in Mott insulators via resonant inelastic x-ray scattering

“…Unfortunately, our calculations also reveal that the signal coming from the emergent gauge field is suppressed by a factor of q 2 , where q is the momentum transferred to the system. Indeed, Raman spectroscopy on herbertsmithite ZnCu 3 (OH) 6 Cl 2 , a possible material realization of the U (1) Dirac spin liquid state, has found a broad continuum in the spectrum that could be attributed to the spinon continuum, but has shown no signs of the emergent gauge field. 4 Given the large momentum carried by x-ray, one would imagine that resonant inelastic x-ray scattering (RIXS) 5 may provide a better prospect of detecting the emergent gauge field.…”