VO ₂ : A two-fluid incoherent metal?

Abstract

We present ab initio LDA+DMFT results for the many-particle density of states of V O2 on the metallic side of the strongly first-order (T -driven) insulator-metal transition. In strong contrast to LDA predictions, there is no remnant of even correlated Fermi liquid behavior in the correlated metal. Excellent quantitative agreement with published photoemission and X-ray absorption experiments is found in the metallic phase. We argue that the absence of FL-quasiparticles provides a natural explanation for the bad-metallic transport for T > 340 K. Based on this agreement, we propose that the I-M transition in V O2 is an orbital-selective Mott transition, and point out the relevance of orbital resolved one-electron and optical spectroscopy to resolve this outstanding issue. A detailed understanding of the above cases is still somewhat elusive. In particular, it is still unclear whether the MIT is orbital selective, i.e., whether different orbital-resolved densities-of-states (DOS) are gapped (driving the Mott insulating state) at different values of U, U ′ (defined below) or whether there is a single (common) Mott transition at a critical interaction strength [3,4]. Conflicting results, even for the same system, and within the same (d = ∞) approximation [4] have been obtained, necessitating more work to resolve this issue.In this communication, we address precisely this issue in vanadium dioxide (V O 2 ). Using the state-of-the-art LDA+DMFT [5] technique, we first show how excellent quantitative agreement with the full, local one-electron spectral function is achieved using LDA+DMFT(IPT). We then build on this agreement, claiming that the MIT in V O 2 is orbital selective, and represents a concrete, ab initio realization of the two-fluid scenario for MIT in strongly correlated systems.V O 2 shows a spectacular MIT at T = 340 K from a low-T monoclinic, Mott insulating phase with spin dimerization along the crystallographic c-axis to a local moment paramagnetic metallic phase. This T -driven MIT has attracted intense scrutiny: because of the additional complication of the antiferroelectric displacement of the V O 6 octahedra in a correlated system, an unambiguous characterization of the MIT (relative importance of MottHubbard versus Peierls dimerization) is somewhat difficult. Various observations have been cited in support of both scenarios [1], and theoretical models detailing the importance of these effects have been proposed [6,7].One-electron spectroscopies constitute a reliable fingerprint of the changes in the single-particle spectral

Dual nature of strongly correlated 5f electrons

“…The latter show that intra-atomic correlations as described by Hund's rules may strongly enhance anisotropies in the kinetic energy and thus lead to an orbital-selective Mott transition in 5f-systems [5,9]. The result, i.e., the splitting of the correlated 5f electrons into itinerant and localized ones parallels the picture postulated recently to explain the behavior of transition metal oxides [10][11][12][13]. We should like to emphasize, however, that the mechanism here is different.…”

Photoemission study of the metal-insulator transition inVO2/TiO2(001):Okazaki1, Wadati2, Fujimori3 et al. 2004Phys. Rev. B10712740View full textAdd to dashboardCite

“…Recently, Liebsch and Ishida 29 proposed that the multi-orbital nature of the V 3d band is important to describe the metallic phase of VO 2 (Ref. 29,30), following the idea originally proposed by Zylbersztejn and Mott. 31 According to these works, the occupancy of the t 2g orbitals is very different between the metallic and the insulating phases due to lattice distortion in the insulating phase and this affects the role of local Coulomb interaction in each phase.…”

Electrodynamics of the vanadium oxidesVO2andV2O3Qazilbash1, Schafgans2, Burch3 et al. 2008Phys. Rev. B261251482View full textAdd to dashboardCite

“…[5][6][7][8][9] There has been much controversy on the driving mechanism of the MIT in VO 2 , and over the relative importance of the Peierls scenario within the single particle picture and electronic correlations representing Mott physics. [5][6][7][8][9][11][12][13][14][15][16][17][18][19][20][21] We have recently demonstrated divergent effective quasiparticle mass in VO 2 as evidence that the MIT is a Mott transition. [22][23][24] There is, however, a structural compo-nent to the phase transition in the form of a Peierls instability ͑charge density wave͒ in the monoclinic insulating ͑M 1 ͒ phase of VO 2 which leads to unit cell doubling and the formation of vanadium dimers ͑pairs͒ along the c axis ͑in the rutile basis͒.…”