Valence-band electronic structure of V2O3: Identification of V and O bands (original) (raw)
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Coherent Peaks and Minimal Probing Depth in Photoemission Spectroscopy of Mott-Hubbard Systems
Physical Review Letters, 2006
We have measured hard x-ray photoemission spectra of pure vanadium sesquioxide (V 2 O 3 ) across its metal-insulator transition. We show that, in the metallic phase, a clear correlation exists between the shakedown satellites observed in the vanadium 2p and 3p core-level spectra and the coherent peak measured at the Fermi level. Comparing experimental results and dynamical mean-field theory calculations, we estimate the Hubbard energy U in V 2 O 3 (4:20 0:05 eV). From our bulk-sensitive photoemission spectra we infer the existence of a critical probing depth for investigating electronic properties in strongly correlated solids.
VO: A strongly correlated metal close to a Mott-Hubbard transition
Physical Review B, 2007
Here we present experimental and computational evidences to support that rock-salt cubic VO is a strongly correlated metal with Non-Fermi-Liquid thermodynamics and an unusually strong spin-lattice coupling. An unexpected change of sign of metallic thermopower with composition is tentatively ascribed to the presence of a pseudogap in the density of states. These properties are discussed as signatures of the proximity to a magnetic quantum phase transition. The results are summarized in a new electronic phase diagram for the 3d monoxides, which resembles that of other strongly correlated systems. The structural and electronic simplicity of 3d monoxides make them ideal candidates to progress in the understanding of highly correlated electron systems.
2021
The Mott metal-insulator transition is at the heart of the essential physics in a strong correlation system as many novel quantum phenomena occur at the metallic phase near the Mott metal-insulator transition. We investigate the Mott metal-insulator transition in a strong correlation system based on the Hubbard model. The average number of the bound electrons evaluated by the dynamical mean-field theory is employed to depict the Mott metal-insulator transition. In comparison with the corresponding quasiparticle coherent weight, the average number of bound electrons is a more proper order parameter to accurately determine the critical point of the Mott metal-insulator transition. Moreover, this order parameter also gives a consistent description of two distinct forms of the critical points in the Mott metal-insulator transition.
3), representative of strongly correlated electronic system, has been known as undergoing the MIT (Metal-Insulator-Transition) which is between rhombohedral paramagnetic metallic phase and monoclinic antiferromagnetic insulating phase near the transition temperature, (T c) ≈150 K. In order to reveal a relation between electronic and structural atomic transition, we has measured the temperature dependence of DC conductivity and structural crystallographic characterization with various temperatures from 90 K to 300 K by using low-temperature X-Ray diffraction (LTXRD). The obtained results show a discrepancy of structural and electronic transitions. This discrepancy can be explained by forming of the metallic puddles whose the size and number increased by nucleation and percolation[1,2] during the electronic transition progress from 120 K to 180 K. The puddles have an insulating monoclinic structure before the structural phase transition at ∼185 K. These metallic puddles are induced by the MIT not related to the SPT (structure phase transition). (1. M.
Metal-insulator transition in pure and Cr-doped V 2 O 3
On the basis of our theoretical examination of the insulating state of V203 reported in the preceding two papers and the experimental results of NMR and susceptibility measurements of the metallic phase, we conjecture the highly correlated electron-gas character in this latter phase of V203. We present arguments for the first-order metal-insulator transition which we consider to be entropy driven passing from the insulating state to a paramagnetic metallic one of nearly equal inner energy but considerably difFerent entropy due to the breakdown of the magnetic and orbital long-range order present in the insulating phase. We believe that the origin of the highly correlated electron gas in the paramagnetic metallic phase lies in the stability of the electronic molecular state of the V pairs along the c axis which persist through the metallic phase, a picture which estimates extremely well the observed entropy in this phase. The lattice distortion observed in the insulating phase is believed to be purely magnetostrictive and of no direct importance to the transition mechanism.
Photoemission evidence for a Mott-Hubbard metal-insulator transition in VO2
Physical Review B, 2008
The temperature (T ) dependent metal-insulator transition (MIT) in VO2 is investigated using bulk sensitive hard x-ray (∼ 8 keV) valence band, core level, and V 2p-3d resonant photoemission spectroscopy (PES). The valence band and core level spectra are compared with full-multiplet cluster model calculations including a coherent screening channel. Across the MIT, V 3d spectral weight transfer from the coherent (d 1 C final) states at Fermi level to the incoherent (d 0 +d 1 L final) states, corresponding to the lower Hubbard band, lead to gap-formation. The spectral shape changes in V 1s and V 2p core levels as well as the valence band are nicely reproduced from a cluster model calculations, providing electronic structure parameters. Resonant-PES finds that the d 1 L states resonate across the V 2p-3d threshold in addition to the d 0 and d 1 C states. The results support a Mott-Hubbard transition picture for the first order MIT in VO2.
Orbital Switching and the First-Order Insulator-Metal Transition in Paramagnetic V2O3
Physical Review Letters, 2003
The first-order metal-insulator transition (MIT) in paramagnetic V2O3V_{2}O_{3}V2O3 is studied within the ab-initio scheme LDA+DMFT, which merges the local density approximation (LDA) with dynamical mean field theory (DMFT). With a fixed value of the Coulomb U=6.0eVU=6.0 eVU=6.0eV, we show how the abrupt pressure driven MIT is understood in a new picture: pressure-induced decrease of the trigonal distortion within the strong correlation scenario (which is not obtained within LDA). We find good quantitative agreement with (i)(i)(i) switch of the orbital occupation of (a1g,eg1pi,eg2pi)(a_{1g},e_{g1}^{\pi}, e_{g2}^{\pi})(a1g,eg1pi,eg2pi) and the spin state S=1 across the MIT, (ii)(ii)(ii) thermodynamics and dcdcdc resistivity, and (iii)(iii)(iii) the one-electron spectral function, within this new scenario.
Physical Review B, 2008
We investigate a quarter-filled two-band Hubbard model involving a crystal-field splitting, which lifts the orbital degeneracy as well as an inter-orbital hopping (inter-band hybridization). Both terms are relevant to the realistic description of correlated materials such as transition-metal oxides. The nature of the Mott metal-insulator transition is clarified and is found to depend on the magnitude of the crystal-field splitting. At large values of the splitting, a transition from a two-band to a oneband metal is first found as the on-site repulsion is increased and is followed by a Mott transition for the remaining band, which follows the single-band (Brinkman-Rice) scenario well documented previously within dynamical mean-field theory. At small values of the crystal-field splitting, a direct transition from a two-band metal to a Mott insulator with partial orbital polarization is found, which takes place simultaneously for both orbitals. This transition is characterized by a vanishing of the quasiparticle weight for the majority orbital but has a first-order character for the minority orbital. It is pointed out that finite-temperature effects may easily turn the metallic regime into a bad metal close to the orbital polarization transition in the metallic phase.
A microscopic view on the Mott transition in chromium-doped V2O3
Nature Communications, 2010
PACS numbers: 71.30.+h, 78.30.-j, 62.50.+p V 2 O 3 is the prototype system for the Mott transition, one of the most fundamental phenomena of electronic correlation. Temperature, doping or pressure induce a metal to insulator transition (MIT) between a paramagnetic metal (PM) and a paramagnetic insulator (PI). This or related MITs have a high technological potential, among others for intelligent windows and field effect transistors. However the spatial scale on which such transitions develop is not known in spite of their importance for research and applications. Here we unveil for the first time the MIT in Cr-doped V 2 O 3 with submicron lateral resolution: with decreasing temperature, microscopic domains become metallic and coexist with an insulating background. This explains why the associated PM phase is actually a poor metal. The phase separation can be associated with a thermodynamic instability near the transition. This instability is reduced by pressure which drives a genuine Mott transition to an eventually homogeneous metallic state.