Evolution of a band insulating phase from a correlated metallic phase

Abstract

We investigate the evolution of the electronic structure in SrRu_(1-x)Ti_xO_3 as a function of x using high resolution photoemission spectroscopy, where SrRuO3 is a weakly correlated metal and SrTiO3 is a band insulator. The surface spectra exhibit a metal-insulator transition at x = 0.5 by opening up a soft gap. A hard gap appears at higher x values consistent with the transport properties. In contrast, the bulk spectra reveal a pseudogap at the Fermi level, and unusual evolution exhibiting an apparent broadening of the coherent feature and subsequent decrease in intensity of the lower Hubbard band with the increase in x. Interestingly, the first principle approaches are found to be sufficient to capture anomalous evolutions at high energy scale. Analysis of the spectral lineshape indicates strong interplay between disorder and electron correlation in the electronic properties of this system.Comment: 4 figure

Ab initioand photoemission study of correlation effects in SrRuO3thin films

“…9,11,12,22,23 Our results show that high photon energy and low emission angle (α = 8 • , L ∼ 1.5, and 2.1 ML at hν = 3000 and 4500 eV, respectively) HAXPES spectra represent the intrinsic (α = 90 • , L ∼ 10.7 and 15 ML at hν = 3000 and 4500 eV, respectively) SrRuO 3 electronic structure, with coherent Ru 4d states remaining dominant at the surface. These spectra are in agreement with the Ru 4d PSW obtained from more surface-sensitive [λ 60 ∼ 2 ML (Ref.…”

“…8 Due to highly extended nature of 4d orbitals, it is natural to assume that correlation effects in 4d transition metal oxides should be weak. Yet in the literature there are several studies indicating the presence of either weak [9][10][11][12] or strong [13][14][15][16] electron correlation in SrRuO 3 . As this issue is of a particular importance, one has to carefully apply experimental and theoretical means while dealing with it.…”

Local theory for Mott-Anderson localization

“…The simultaneous presence of disorder (W ) and interaction (U ) effects is known to influence material properties in subtle ways. Over the last few decades, several experimental works on a range of systems 1,[7][8][9][10][11][12][13][14] have highlighted the importance of the interplay of disorder and interactions. The early theoretical studies of such systems 15 mainly focused on the weak disorder limit, perturbing around Fermi liquid theory.…”

Theoretical and experimental study of non-stoichiometric SrRuO₃ : a role of oxygen vacancies in electron correlation effects

“…2), the sharp peak A (FWHM = 0.55 eV) in the vicinity of E F may be assigned to the coherent part of the spectral function. The broader peak B (FWHM = 0.93 eV) may be recognized as the incoherent part of the spectral function [25,26], not present in DFT calculations, whereas the broadest peak C (FWHM = 1.1 eV) may be attributed to the tail of asymmetric shape of the coherent feature and stronger admixture of O 2p states in the dominant Ru 4d region [10]. Figure 3 illustrates the evolution of relative intensities for different spectral components under heat treatment and subsequent argon sputtering.…”