Showing papers on "Mott insulator published in 1993"
TL;DR: Using a combination of perturbation theory and quantum Monte Carlo, this work elucidate the behavior of the single-particle Green's function and the local spin-spin correlation function near the Mott transition in the infinite dimensional Hubbard model at half filling.
Abstract: Using a combination of perturbation theory and quantum Monte Carlo, we elucidate the behavior of the single-particle Green's function and the local spin-spin correlation function near the Mott transition in the infinite dimensional Hubbard model at half filling. The model has three fixed points: the Fermi liquid phase qualitatively described by the Brinkman-Rice picture, the insulating phase resembling Hubbard's solution, and an unstable Mott point which connects the two.
247 citations
TL;DR: In this paper, the first reliable analytic calculation of the phase diagram of the bose gas on a $d$-dimensional lattice with on-site repulsion is presented, and explicit expressions for the energy of the Mott and the ''defect'' phase are given in a strong-coupling expansion.
Abstract: The first reliable analytic calculation of the phase diagram of the bose gas on a $d$-dimensional lattice with on-site repulsion is presented. In one dimension, the analytic calculation is in excellent agreement with the numerical Monte Carlo results. In higher dimensions, the deviations from the Monte Carlo calculations are larger, but the correct shape of the Mott insulator lobes is still obtained. Explicit expressions for the energy of the Mott and the ``defect'' phase are given in a strong-coupling expansion.
113 citations
TL;DR: At low temperatures, the phase transition is investigated by mapping the model onto a XXZ spin-1/2 Heisenberg model and finding lobes of insulating phase characterized by integer fillings for finite-range interactions-lobes with rational filling factors.
Abstract: We study the superconductor-insulator transition of Bose-Hubbard models with finite-range interactions. Commensurability of the charge distribution with the underlying lattice leads to a richly structured phase diagram. In addition to the lobes of insulating phase characterized by integer fillings, we find-for finite-range interactions-lobes with rational filling factors. At low temperatures we can investigate the phase transition by mapping the model onto a XXZ spin-1/2 Heisenberg model.
75 citations
TL;DR: Transitions between two quantum Hall states or between a quantum Hall state and a Mott insulator induced by periodic potentials are studied in the 1/N expansion and are described by a critical point that depends on a real parameter θ, which is determined by the topological orders in the quantum HallStates involved in the transition.
Abstract: Transitions between two quantum Hall states or between a quantum Hall state and a Mott insulator induced by periodic potentials are studied in the 1/N expansion. The transitions are found to be continuous in the large-N limit and are described by a critical point that depends on a real parameter \ensuremath{\theta}, which is determined by the topological orders in the quantum Hall states involved in the transition. Some critical exponents and universal quantities are calculated in the large-N limit and shown to be \ensuremath{\theta} dependent.
67 citations
TL;DR: In this paper, it was shown that a spin gap opens and the linear coefficient of the specific heat decreases and then vanishes at the transition point of MT2 in sharp contrast with MT1.
Abstract: One type of Mott transition (MT1) is characterized by diverging enhancement of the charge effective mass when one approaches a Mott insulator from the side of the paramagnetic metal. Another fundamentally different type of Mott transition (MT2) is shown to exist when a spin gap opens. The linear coefficient of the specific heat γ decreases and then vanishes at the transition point of MT2 in sharp contrast with MT1. As an example, a dimerized t - J model is shown to undergo MT2. The underlying pairing mechanism determines the character of MT2. Recent controversial experimental results on the Mott transitions in copper oxides and other strongly correlated systems are discussed from the above viewpoint.
64 citations
TL;DR: The electronic structure and Fermi surface of the recently discovered HgBa2Can-1CunO2n+2+δ superconductors have been determined using the full potential linear muffin-tin orbital method and precise structural information determined with neutrons by Radaelli et al. as mentioned in this paper.
Abstract: The electronic structure and Fermi surface of the recently discovered HgBa2Can-1CunO2n+2+δ superconductors have been determined using the full potential linear muffin-tin orbital method and precise structural information determined with neutrons by Radaelli et al. Whereas for stoichiometric HgBa2CuO4 (Hg-1201) the only band crossing the Fermi energy derived from the CuO antibonding state is half-filled, an additional HgO band that crosses EF exists in the case of HgBa2CaCu2O6 (Hg-1212) and HgBa2Ca2CuO4O8 (Hg-1223). Thus, stoichiometric HgBa2CuO4 is expected to be a Mott insulator with dopants essential for forming the normal metallic state that leads to superconductivity at 95 K, in contrast to two other members of the Hg family that are expected to be “self-doped” to a metallic normal state. As in Hg-1201, the electronic structure is two-dimensional and is dominated by van Hove singularities (vHS's) to which EF is pinned by dopants whose calculated concentration is found to agree well with that determined by Radaelli et al. for Hg-1212 for their maximum Tc = 128 K sample. Finally, predicted doping levels for stabilizing a large volume of the high-Tc Hg-1223 phase - and hence its highest Tc - are made on the basis of pinning E F to the vHS.
52 citations
TL;DR: Using a simple variational ansatz, this work estimates the pair wave function or a superconductor obtained by doping a Mott insulator with short-range antirerromagnetic spin correlations, which is generically d wave.
Abstract: Using a simple variational ansatz, we estimate the pair wave function or a superconductor obtained by doping a Mott insulator with short-range antirerromagnetic spin correlations. The pairing symmetry is generically d wave. The so-called «anyon superconductors» are related to traditional BCS states with d-wave order parameters that break parity and time-reversal invariance. The transition between a tetragonal normal metal and a superconductor or this type generically proceeds through an intermediate phase with either superconducting order or broken time reversal, but not both
43 citations
TL;DR: In this paper, the authors studied the magnetic properties of Sc-doped TiOX, seeking possible indications of the existence of the resonant valence bond or RVB state-the state currently suggested by some to be responsible for high-temperature superconductivity in the mixed-valence cuprates.
Abstract: The title materials display anomalous electrical, magnetic and optical properties. They have the characteristics of Mott insulators showing high electrical resistance and ligand-field optical spectra, but at the same time they adopt a magnetic ground state which is neither of Curie-Weiss type nor indeed of some standard antiferromagnetically ordered condition. The observed state is one of lowish, isotropic, and almost temperature-independent paramagnetism. The authors have studied the magnetic properties of Sc-doped TiOX, seeking possible indications of the existence of the resonant valence bond or RVB state-the state currently suggested by some to be responsible for high-temperature superconductivity in the mixed-valence cuprates. It is necessary to distinguish between RVB and some extreme case of magnetic frustration in these S=1/2, 2D oxyhalide systems. The authors' tentative conclusion is that TiOX presents an RVB ground state which Sc doping renders glassy and static.
34 citations
TL;DR: In this article, local density approximation calculations of the electronic structure of HgBa 2 CuO 4 are reported along with a number of properties identifiable from it, including superconductivity.
Abstract: Local density approximation calculations of the electronic structure of HgBa 2 CuO 4 are reported along with a number of properties identifiable from it. For the stoichiometric material, the only band crossing the Fermi energy is the Cu-O derived antibonding state characteristic of high- T c cuprates; this band is half-filled. Thus, the stoichiometric material is expected to be a Mott insulator, as are the other undoped cuprates, and the excess oxygen reported in the as-synthesized material is no doubt essential for its superconductivity. Electric field gradients are calculated and compared with those in other cuprates. The position wave-function has maximum weight in the rather large holes in the Hg layer. However, unlike the majority of high- T c materials, there is substantial weight throughout the unit cell, including the Cu-O layer region.
31 citations
TL;DR: The one-dimensional Hubbard model is characterized by charge-spin separation, but nevertheless in the doped system σ(ω>0) does not vanish due to a small remaining coupling between charge and spin degrees of freedom, and an effective Hamiltonian is derived.
Abstract: The one-dimensional Hubbard model is characterized by charge-spin separation, but nevertheless in the doped system σ(ω>0) does not vanish due to a small remaining coupling between charge and spin degrees of freedom. We derive an effective Hamiltonian and give in leading order (∼J 2 ) an analytic expression for σ(ω) for the case of the Mott insulator doped with one hole. The complete frequency dependence in the strong-coupling limit of the Hubbard model and for the t-J model agrees with results from exact diagonalization. The limit σ(ω→0) at T=0 is found to be very different for the two models, i.e., ∼ω 3/2 in the strong-coupling limit and ∼ω -1/2 for the t-J model
13 citations
TL;DR: Using an approximate solution of the Hubbard-model Hamiltonian, it is able to establish that the Cs-GaAs(110) system becomes a Mott insulator at submonolayer Cs coverages.
Abstract: Using an approximate solution of the Hubbard-model Hamiltonian, we are able to establish that the Cs-GaAs(110) system becomes a Mott insulator at submonolayer Cs coverages We also provide a consistent interpretation of electron-energy-loss and scanning-tunneling-spectroscopies data The correlation effects are important for this system with an estimated correlation energy of 04 eV
TL;DR: The transition for a one-dimensional collection of spinless interacting charged particles from metal to a Mott insulator phase is shown to exhibit two kinds of universal jump of conductance.
Abstract: The transition for a one-dimensional collection of spinless interacting charged particles from metal to a Mott insulator phase is shown to exhibit two kinds of universal jump of conductance: when the filling factor is p/q, where p and q are irreducible integers and q gives the order of backward scattering responsible for localization, there is a jump ${\mathit{e}}^{2}$/${\mathit{q}}^{2}$h along the metal-insulator phase boundary, but at special points with particle-hole symmetry the universal jump of conductance is exactly twice as large. Even far inside the metal phase, where the Mott insulator does not occur, its existence is manifested by a singularity in the conductance at the corresponding rational filling. Most of the results hold also for the case of Mott localization in a quasiperiodic potential. The only essential difference here is that insulator phases are characterized by filling factors which are, in general, irrational numbers: for a quasiperiodic potential with a ratio of fundamental incommensurate length \ensuremath{\sigma} the insulator phase is characterized by an irrational filling factor (${\mathit{m}}_{0}$+${\mathit{m}}_{1}$\ensuremath{\sigma})/q, where ${\mathit{m}}_{0,1}$ are integers.
TL;DR: In this paper, high pressure studies using diamond anvil cells were carried out in antiferromagnetic insulator transition metal iodides characterized by their layered structure, which provided a detailed analysis of Mott insulators under high pressure regime and the nature of the pressure induced Mott transition.
Abstract: High pressure studies using Diamond Anvil Cells were carried out in antiferromagnetic insulator transition metal iodides characterized by their layered structure. Magnetic properties studied by 129 I Mossbauer Spectroscopy, the equation of state obtained from X-ray diffraction and metal insulator transition deduced from R(T, P) provided a detailed analysis of Mott insulators under the high pressure regime and the nature of the pressure induced Mott transition.
TL;DR: In this article, the effects of spin-Peierls fluctuation on one-dimensional strongly correlated systems coupled to dynamical lattice distortion or polarization are examined by quantum Monte Carlo studies.
Abstract: Effects of spin-Peierls fluctuation are examined in models of one-dimensional conductors. One-dimensional strongly correlated systems coupled to dynamical lattice distortion or polarization are examined by quantum Monte Carlo studies. Excitations are given by spinless charge solitons and neutral spin solitons when the system is doped away from a Mott insulator. A pairing mechanism due to a dynamical spin-Peierls fluctuation is discussed. Numerical results on the spin gap formation and the enhancement of pairing correlations in a dimerized t-J model and doped spin-1 Heisenberg model in one dimension are summarized
TL;DR: In this paper, the Mott transition on a square lattice has been studied by the quantum Monte Carlo method and critical exponents of the metal-insulator transition estimated for charge and spin correlations are summarized.
Abstract: The Hubbard model on a square lattice has been studied by the quantum Monte Carlo method. The nature of the Mott transition upon hole doping is investigated. Critical exponents of the metal-insulator transition estimated for charge and spin correlations are summarized. We stress that a new theoretical framework should be constructed to understand these results. Comparisons with experimental results on high-Tc oxides are also made.
TL;DR: The rule relating the observed Hall coefficient to the spin and charge responses of the uniform doped Mott insulator is derived and it is essential to include the contribution of holon and spinon three-current correlations to the effective action of the gauge field.
Abstract: The rule relating the observed Hall coefficient to the spin and charge responses of the uniform doped Mott insulator is derived. It is essential to include the contribution of holon and spinon three-current correlations to the effective action of the gauge field. In the vicinity of the Mott insulating point the Hall coefficient is holon dominated and weakly temperature dependent. In the vicinity of a point of charge conjugation symmetry, the holon contribution to the observed Hall coefficient is small: the Hall coefficient follows the temperature dependence of the diamagnetic susceptibility with a sign determined by the Fermi-surface shape
01 Jan 1993
TL;DR: In this paper, the authors exploited the large field gradients in the vicinity of the STM tip to induce the directional diffusion of Cs and K atoms adsorbed on room temperature GaAs(110) and InSb(110).
Abstract: Field ion microscopists demonstrated more than twenty years ago that polarizable atoms adsorbed on a stepped surface can be induced to diffuse by an electric field due to the field gradients associated with step edges. We have exploited a similar phenomenon, the large field gradients in the vicinity of the STM tip, to induce the directional diffusion of Cs and K atoms adsorbed on room temperature GaAs(110) and InSb(110). The geometric and electronic properties of both the naturally occurring and electric field-induced alkali metal structures observed on these semiconductor surfaces are discussed, including the possibility that the alkali metal overlayers are Mott insulators.
TL;DR: The origin of the semiconducting properties of the molybdenum bronze Sb 4 Mo 20 O 62 was examined by performing tight-binding electronic band structure calculations as discussed by the authors.
TL;DR: The role of the electron correlation manifested itself in filling-dependent enhancement of the density of states at the Fermi level, carrier scattering rate and spin susceptibility on the verge of the metal-insulator transition as discussed by the authors.
Abstract: Crossover behavior of electronic structures from Mott insulator to Pauli metal has been investigated as a function of filling in titanium oxide compounds with perovskite-like structures. The role of the electron correlation manifests itself in filling-dependent enhancement of the density of states at the Fermi level, carrier scattering rate and spin susceptibility on the verge of the metal-insulator transition.
TL;DR: In this paper, the spin-Peierls t-J model is shown to be a relevant model for electron-phonon coupling in strongly correlated metals and its experimental consequences and possible relevance in high Tc oxides and fullerenes are also discussed.
Abstract: A characteristic and unique feature of electron-phonon coupling in strongly correlated metals is examined. Significant properties due to spin-Peierls fluctuation near the Mott transition recently clarified are reviewed, especially in terms of the pairing mechanism and spin gap formation in the metallic phase. A superconducting state appears when the singlet ground state of a Mott insulator with a spin gap is doped with metallic carriers. The spin-Peierls t-J model is shown to be a relevant model. Exotic features of the spin-Peierls pairing mechanism are discussed. Experimental consequences and possible relevance in high Tc oxides and fullerenes are also discussed.
01 Jan 1993
TL;DR: The role of the electron correlation in the metal-insulator transitions manifests itself in filling-dependent enhancement of effective electron mass and in doping-induced ingap states in titanium and vanadium oxides with perovskite-like structures as discussed by the authors.
Abstract: Filling-dependent electronic structures in titanium and vanadium oxides with perovskite-like structures have been investigated by measurements of optical conductivity spectra as well as by characterization of transport and magnetic properties. With use of orthorhombically distorted solid solutions, (R,A)TiO3 and (R,A)VO3 (R = rare earth and A = alkaline earth ions), a crossover behavior of the electronic states from the Mott insulator to Pauli metal has been unraveled as a function of the fillingness. The role of the electron correlation in the metal-insulator transitions manifests itself in filling-dependent enhancement of effective electron mass and in doping-induced ingap states.
01 Jan 1993
TL;DR: In this paper, a model of bosons on a 2D square lattice with a random potential of strength V and on-site repulsion U was studied and the path integral Monte Carlo algorithm used to simulate this system was described.
Abstract: Interacting bosons in a random potential can be used to model 4He adsorbed in porous media, universal aspects of the superconductor-insulator transition in disordered films, and vortices in disordered type II superconductors. We study a model of bosons on a 2D square lattice with a random potential of strength V and on-site repulsion U. We first describe the path integral Monte Carlo algorithm used to simulate this system. The 2D quantum problem (at T=0) gets mapped onto a classical problem of strings or directed polymers moving in 3D with each string representing the world line of a boson. We discuss efficient ways of sampling the polymer configurations as well as the permutations between the bosons. We calculate the superfluid density and the excitation spectrum. Using these results we distinguish between a superfluid, a localized or ‘Bose glass’ insulator with gapless excitations and a Mott insulator with a finite gap to excitations (found only at commensurate densities). We discover novel effects arising from the interplay between V and U and present preliminary results for the phase diagram at incommensurate and commensurate densities.
01 Jul 1993
TL;DR: In this article, high pressure studies of the insulator-metal transition in the (TM)I2 (TM=V, Fe, Co, and Ni) compounds were described, where resistivity, X-ray diffraction and Mossbauer Spectroscopy were employed to investigate the electronic, structural, and magnetic properties as a function of pressure both on the highly correlated and on the metallic regimes.
Abstract: High pressure studies of the insulator‐metal transition in the (TM)I2 (TM=V, Fe, Co, and Ni) compounds are described. Those divalent transition‐metal iodides are structurally isomorphous and classified as Mott Insulators. Resistivity, X‐ray diffraction, and Mossbauer Spectroscopy were employed to investigate the electronic, structural, and magnetic properties as a function of pressure both on the highly correlated and on the metallic regimes.
01 Jan 1993
TL;DR: In this paper, the authors used quantum Monte Carlo techniques to study the critical properties of an interacting boson model in one dimension with and without disorder, and demonstrate the existence and study the properties of the predicted Bose glass phase as well as an unanticipated Anderson-like insulating regime.
Abstract: We use quantum Monte Carlo techniques to study the critical properties of an interacting boson model in one dimension with and without disorder. In the absence of disorder, the phase diagram consists of a Mott insulating phase at commensurate fillings and a superfluid phase. The effect of disorder is to shrink the Mott insulator phase and to cause the emergence of two new insulating regions. Our simulations are the first to demonstrate the existence and study the properties of the predicted “Bose glass” phase as well as an unanticipated Anderson-like insulating regime. For the uniform system, we study the critical behaviour of the superfluid density and the compressibility, and measure the exponents v and z, which agree with predictions based on a scaling analysis.