Mott transition

About: Mott transition is a research topic. Over the lifetime, 2444 publications have been published within this topic receiving 78401 citations.

Conductivity of n -type GaAs near the Mott transition

Abstract: Low-T transport data on n-type GaAs in several regimes from insulating to metallic is presented. On the insulating side of the Mott transition, it is shown that the power s in the variable-range-hopping law, ${\ensuremath{\sigma}}_{v}$=${\ensuremath{\sigma}}_{0}$exp[-(${T}_{0}$/T${)}^{s}$], which is found to be (1/4 for pure enough samples, can reach (1/2 for a narrow range of higher impurity concentrations. A small metal-like contribution to the conductivity can explain the observed shift in s and is supported by Hall-mobility data. Consequently, the corresponding behavior can hardly be interpreted as due to a Coulomb gap in the density of impurity states. Evidence is presented for weak localization and then normal metallic behavior for higher impurity concentrations.

Kinetic energy driven superconductivity and the pseudogap phase in weakly doped antiferromagnets

Abstract: By analysing an effective Hamiltonian for spin polarons forming in weakly doped antiferromagnets represented by the t– J model we demonstrate that the driving mechanism which gives rise to superconductivity in such a system is the lowering of the kinetic energy, which is consistent with recent experimental observations. That source of attraction between holes is effective if the antiferromagnetic correlation length is longer than the radius of polarons. Notwithstanding that the attraction is strongest in the undoped system with long-range order, the superconducting order parameter vanishes when the doping parameter decreases, which can be attributed to emptying the spin polaron band and approaching the Mott insulator phase. Since the hypothetical normal phase of a low-density gas of fermions is unstable against formation of bound hole pairs the intensity of low-energy excitations is suppressed and a pseudogap forms in the underdoped region.

Direct Observation of the Bandwidth Control Mott Transition in the NiS 2-x Se x Multiband System

Abstract: The bulk electronic structure of ${\mathrm{NiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ has been studied across the bandwidth-control Mott transition (BCMT) using soft x-ray angle-resolved photoemission spectroscopy. We show that Se doping does not alter the Fermi surface volume. When approaching the insulating phase with decreasing Se concentration, we observed that the Fermi velocity continuously decreases. Meanwhile, the weight of the coherent quasiparticle, which sits on a large incoherent spectrum, continuously decreases and is transferred to higher binding energies, until it suddenly disappears across the Mott transition. In the insulating phase, there is still finite spectral weight at the Fermi energy, but it is incoherent and dispersionless due to strong correlations. Our results provide a direct observation of the distinct characters of BCMT in a multiband non-half-filled system.

Mott transition in two-dimensional frustrated compounds

Abstract: The phase diagrams of isotropic and anisotropic triangular lattices with local Coulomb interactions are evaluated within cluster dynamical mean field theory. As a result of partial geometric frustration in the anisotropic lattice, short range correlations are shown to give rise to reentrant behavior which is absent in the fully frustrated isotropic limit. The qualitative features of the phase diagrams including the critical temperatures are in good agreement with experimental data for the layered organic charge transfer salts kappa-(BEDT-TTF)_2Cu[N(CN)_2]Cl and kappa-(BEDT-TTF)_2Cu_2(CN)_3.

Direct observation of the M2 phase with its Mott transition in a VO2 film

Abstract: In VO2, the explicit origin of the insulator-to-metal transition is still disputable between Peierls and Mott insulators. Along with the controversy, its second monoclinic (M2) phase has received considerable attention due to the presence of electron correlation in undimerized vanadium ions. However, the origin of the M2 phase is still obscure. Here, we study a granular VO2 film using conductive atomic force microscopy and Raman scattering. Upon the structural transition from monoclinic to rutile, we observe directly an intermediate state showing the coexistence of monoclinic M1 and M2 phases. The conductivity near the grain boundary in this regime is six times larger than that of the grain core, producing a donut-like landscape. Our results reveal an intra-grain percolation process, indicating that VO2 with the M2 phase is a Mott insulator.