Prominent Quasiparticle Peak in the Photoemission Spectrum of the Metallic Phase ofV2O3

Abstract

We present the first observation of a prominent quasi-particle peak in the photoemission spectrum of the metallic phase of V2O3 and report new spectral calculations that combine the local density approximation with the dynamical mean-field theory (using quantum Monte Carlo simulations) to show the development of such a distinct peak with decreasing temperature. The experimental peak width and weight are significantly larger than in the theory.PACS numbers: PACS numbers: 71.20. Be, 71.30.+h, (V 1−x Cr x ) 2 O 3 displays a complex phase diagram with paramagnetic metal (PM), paramagnetic insulator (PI) and antiferromagnetic insulator (AFI) regions. The PM to PI transition serves as the paradigm of the MottHubbard (MH) metal-insulator transition (MIT) [1]. The MH scenario for (V 1−x Cr x ) 2 O 3 was put forth originally in the context of the half-filled one-band Hubbard model in which the tendency of the on-site Coulomb repulsion 'U ' to make a correlation gap insulator competes with the tendency of site to site hopping to make a broad band metal of bandwidth 'B'. A coherent thermodynamically consistent description of the MIT became possible with the development of the dynamical mean-field theory (DMFT) [2]. DMFT describes the strongly interacting metal in terms of Fermi liquid quasi-particles, i.e. single particle excitations near the Fermi energy E F which remain well defined as in a non-interacting system but have a self energy correction that increases their effective mass and reduces their spectral weight. In application to the Hubbard model, DMFT is significant as the best description that can be made by using a local (i.e. independent of momentum k) self energy. It may be formulated as a mapping of the lattice problem onto an effective Anderson impurity model coupled self-consistently to an effective conduction band bath [3]. In the metallic phase, although the large U value acts to separate much of the band's spectral weight away from E F into the so called upper and lower Hubbard bands, there remains at E F a distinctive quasi-particle (QP) peak, not accidentally reminiscent of the Kondo/Suhl-Abrikosov resonance [4] of the Anderson impurity model. The weight of the QPpeak decreases with increasing U/B and goes to zero at a critical value of U/B, which thus marks the MIT.Such a distinctive peak could in principle be seen in photoemission spectroscopy (PES). However, in spite of continuing efforts for over twenty years, literature [5,6,7,8,9, 10] V 3d PES spectra for the PM phase of (V 1−x Cr x ) 2 O 3 have shown at most a near E F feature that is the smallest part of the spectrum. One could hypothesize that the distinctive central peak of the halffilled one-band model is obscured and washed out by the multi-band complexity of the actual electronic structure of (V 1−x Cr x ) 2 O 3 in which the two 3d-electrons of the V 3+ ion must be distributed among singly degenerate a 1g and doubly degenerate e π g orbitals derived from a small trigonal crystal field splitting of the cubic t 2g manifold of the V 3d states....

Electronic structure ofCeRu2X2(X=Si,Yano1, Sekiyama2, Fujiwara3 et al. 2008Phys. Rev. BSelf Cite515210View full textAdd to dashboardCite

“…However, the bulk sensitivity of the soft X-ray (hν ∼ 800 eV) PES was confirmed by the observation of the 4f PES for Ce compounds. 20 Soft X-ray PES is currently an essential approach to reveal electronic states of transition metal compounds 21,22 and rare earth compounds. 23 In addition, more bulk-sensitive PES by using hard X rays (HAXPES) has become feasible.…”

Thinking locally: Reflections on Dynamical Mean‐Field Theory from a high‐temperature/high‐energy perspective

“…This can be interpreted as due to antiferromagnetic correlations of increasing range, which quenches the entropy of the insulator so that the 'Pomeranchuk effect' does not apply any more. This observation suggests that using single-site DMFT (while taking into account the actual electronic structure of the material) to describe the metalinsulator transition of V 2 O 3 at temperatures around the critical endpoint T c ≃ 450K but also significantly below that scale is quite reasonable (as indeed has been done successfully [21][22][23][24][25]). In contrast, the range of applicability of single-site DMFT is probably more limited for the organic materials when considering the low pressure regime close to the insulating phase.…”

Strongly Correlated Electron Materials: Dynamical Mean-Field Theory and Electronic Structure

“…For the metallic phase of V 2 O 3 , high photon energy photoemission proved to be an essential tool in the recent experimental finding of the quasiparticle peak (Fig. 12) by Mo et al [97].…”

“…Photoemission spectra of V 2 O 3 , for various photon energies, from Ref. [97]. The highest photon energy spectrum, corresponding to the greatest bulk sensitivity, reveals a prominent quasiparticle peak.…”