Showing papers on "Mott transition published in 2001"
TL;DR: In this paper, the spectral function and self-energy for the Mott-Hubbard model on a Bethe lattice with infinite coordination number directly on the real-frequency axis were calculated.
Abstract: Wilson's numerical renormalization group method for the calculation of dynamic properties of impurity models is generalized to investigate the effective impurity model of the dynamical mean-field theory at finite temperatures. We calculate the spectral function and self-energy for the Hubbard model on a Bethe lattice with infinite coordination number directly on the real-frequency axis and investigate the phase diagram for the Mott-Hubbard metal-insulator transition. While for $Tl{T}_{\mathrm{c}}\ensuremath{\approx}0.02W$ $(W:$ bandwidth) we find hysteresis with first-order transitions both at ${U}_{\mathrm{c}1}$ (defining the insulator to metal transition) and at ${U}_{\mathrm{c}2}$ (defining the metal to insulator transition), at $Tg{T}_{\mathrm{c}}$ there is a smooth crossover from metalliclike to insulatinglike solutions.
233 citations
TL;DR: The results of parameter-free quasiparticle calculations of the single-particle excitation spectrum show that CaB6 is not a semimetal but a semiconductor with a band gap of 0.8+/-0.1 eV.
Abstract: Ferromagnetism was recently observed at unexpectedly high temperatures in La-doped CaB6. The starting point of all theoretical proposals to explain this observation is a semimetallic electronic structure calculated for CaB6 within the local density approximation. Here we report the results of parameter-free quasiparticle calculations of the single-particle excitation spectrum which show that CaB6 is not a semimetal but a semiconductor with a band gap of 0.8±0.1 eV. Magnetism in LaxCa1-xB6 occurs just on the metallic side of a Mott transition in the La-induced impurity band.
134 citations
TL;DR: In this paper, a functional for the single-particle Green's function, which is a variant of the standard Baym-Kadanoff functional, has been constructed, which allows a simple and rigorous derivation of both the standard and extended dynamical mean field equations as stationary conditions.
Abstract: We construct a functional for the single-particle Green's function, which is a variant of the standard Baym-Kadanoff functional. The stability of the stationary solutions to the functional is directly related to aspects of the irreducible particle hole interaction through the Bethe-Salpeter equation. A startling aspect of this functional is that it allows a simple and rigorous derivation of both the standard and extended dynamical mean-field (DMFT) equations as stationary conditions. Though the DMFT equations were formerly obtained only in the limit of infinite lattice coordination, the functional described in the work presents a way of directly extending DMFT to finite-dimensional systems, both on a lattice and in a continuum. Instabilities of the stationary solution at the bifurcation point of the functional signal the appearance of a zero mode at the Mott transition which then couples to physical quantities resulting in divergences at the transition.
87 citations
TL;DR: In this paper, numerical studies on Mott transitions caused by the control of the ratio between bandwidth and electron-electron interaction (U ) are reported. By using the recently proposed pathintegral renorma...
Abstract: Numerical studies on Mott transitions caused by the control of the ratio between bandwidth and electron–electron interaction ( U ) are reported. By using the recently proposed path-integral renorma...
83 citations
TL;DR: The critical behavior shows that the Mott transition is infinite order for all t', whether or not a spin gap is present, and that hyperscaling holds.
Abstract: We study the Mott transition as a function of interaction strength in the half-filled Hubbard chain with next-nearest-neighbor hopping t' by calculating the response to an external electric field using the density matrix renormalization group. The electric susceptibility chi diverges when approaching the critical point from the insulating side. We show that the correlation length xi characterizing this transition is directly proportional to fluctuations of the polarization and that chi approximately xi2. The critical behavior shows that the transition is infinite order for all t', whether or not a spin gap is present, and that hyperscaling holds.
74 citations
TL;DR: In this article, it was shown that the radius of the exciton becomes a strong function of the detuning, and, in screened systems, the coupling with the photons can preclude the Mott transition.
48 citations
TL;DR: In this article, the authors studied the zero-temperature phase transition between a d-wave superconductor and a Mott insulator in two dimensions, where spin and charge are confined to form the electron in the Mott interior.
Abstract: We study the nature of the zero-temperature phase transition between a d-wave superconductor and a Mott insulator in two dimensions. In this ``quantum confinement transition,'' spin and charge are confined to form the electron in the Mott insulator. Within a dual formulation, direct transitions from d-wave superconductors at half-filling to insulators with spin-Peierls (as well as other) order emerge naturally. The possibility of striped superconductors is also discussed within the dual formulation. The transition is described by nodal fermions and bosonic vortices, interacting via a long-ranged statistical interaction modeled by two coupled Chern-Simons gauge fields, and the critical properties of this model are discussed.
47 citations
TL;DR: In this article, the structural, transport, and magnetic properties of both polycrystalline and single-crystal samples are fully in agreement for the quasi-two-dimensional Mott transition system Ca{sub 2-x}Sr{sub x}RuO{sub 4}.
43 citations
TL;DR: Mid-infrared pump-probe measurements with subpicosecond time resolution reveal the existence of a metastable condensed phase of the electron-hole ensemble in a direct-gap semiconductor CuCl, and the observed resonance feature at Planck's over 2pi(omega)p/sqrt[3] allows us to obtain the carrier density in the metastable electron- hole droplets.
Abstract: Mid-infrared pump-probe measurements with subpicosecond time resolution reveal the existence of a metastable condensed phase of the electron-hole ensemble in a direct-gap semiconductor CuCl. High-density electrons and holes are directly created in a low-temperature state by the resonant femtosecond excitation of excitons above the Mott transition density. Strong metallic reflection with a plasma frequency Planck's over 2pi(omega)p approximately 0.5 eV builds up within 0.3 ps. Within a few picoseconds, the mid-infrared reflection spectrum is transformed from metalliclike into colloidlike. The observed resonance feature at Planck's over 2pi(omega)p/sqrt[3] allows us to obtain the carrier density in the metastable electron-hole droplets of 2x10(20) cm(-3).
38 citations
TL;DR: In this paper, the Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory recently developed by Bulla and Potthoff.
Abstract: The Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory recently developed by Bulla and Potthoff. The phase boundary of the metal-insulator transition is obtained analytically as a function of the on-site Coulomb interaction at the d-orbital, the charge-transfer energy between the d- and p-orbitals and the hopping integrals between p-d, d-d and p-p orbitals. The result is in good agreement with the numerical results obtained from the exact diagonalization method.
34 citations
TL;DR: In this article, the interplay between geometrical frustration and strong electron correlation based upon the pyrochlore Hubbard model is investigated, and the self-energy shows a divergent behavior leading the system into the Mott insulating state, in which a quantum disordered spin liquid without magnetic long-range order is realized.
Abstract: We investigate the interplay between geometrical frustration and strong electron correlation based upon the pyrochlore Hubbard model. In the half-filling case, using the perturbative expansion in terms of electron correlation, we show that the self-energy shows a divergent behavior leading the system into the Mott insulating state, in which a quantum disordered spin liquid without magnetic long-range order is realized. In the hole-doped case, we obtain heavy-fermion-like Fermi-liquid state. We also calculate the neutron cross section, which is very consistent with recent neutron scattering experiments for itinerant pyrochlore systems.
TL;DR: In this article, the authors show that the qualitative behavior in the insulating phase is model independent, and that a number of new features arise as one approaches the metal-insulator transition from the Fermi-liquid phase.
Abstract: A wide variety of strongly correlated materials including ${\mathrm{SmB}}_{6},$ FeSi, and the underdoped cuprates display anomalous behavior in their Raman response, which includes a low-temperature transfer of spectral weight from low to high energy (as T is reduced) and the appearance of an isosbestic point (a characteristic frequency where the Raman response is independent of temperature). We illustrate how these features appear in the Raman response of the infinite-dimensional Hubbard model, which is the simplest system to undergo the Mott transition from a Fermi liquid phase. We find that the qualitative behavior in the insulating phase is model independent, and that a number of new features arise as one approaches the metal-insulator transition from the Fermi-liquid phase. Such behavior has not yet been seen in experiment. We propose a number of different systems that are likely to show these new anomalies.
TL;DR: In this article, the effect of electron correlation on metal-insulator transitions induced by the control of the width and the filling of the Ti and V 3D bands was investigated. But the authors focused on the metal-inulator transitions.
TL;DR: In this article, the authors studied the effect of carrier interaction induced many-body effects on the excitonic optical properties of highly photoexcited one-dimensional semiconductor quantum wire systems by solving the dynamically screened Bethe-Salpeter equation using realistic Coulomb interaction between carriers.
Abstract: We study carrier interaction induced many-body effects on the excitonic optical properties of highly photoexcited one-dimensional semiconductor quantum wire systems by solving the dynamically screened Bethe-Salpeter equation using realistic Coulomb interaction between carriers. Including dynamical screening effects in the electron/hole self-energy and in the electron-hole interaction vertex function, we find that the excitonic absorption is essentially peaked at a constant energy for a large range of photoexcitation density ($n= 0-6\times 10^5$ cm$^{-1}$), above which the absorption peak disappears without appreciable gain i.e., \textit{no} exciton to free electron-hole plasma Mott transition is observed, in contrast to previous theoretical results but in agreement with recent experimental findings. This absence of gain (or the non-existence of a Mott transition) arises from the strong inelastic scattering by one-dimensional plasmons or charge density excitations, closely related to the non-Fermi liquid nature of one-dimensional systems. Our theoretical work demonstrates a transition or a crossover in one-dimensional photoexcited electron-hole system from an effective Fermi liquid behavior associated with a dilute gas of noninteracting excitons in the low density region ($n 10^5$ cm$^{-1}$). The conventional quasi-static approximation for this problem is also carried out to compare with the full dynamical results. Numerical results for exciton binding energy and absorption spectra are given as functions of carrier density and temperature.
TL;DR: In this article, the authors studied how conservation laws affect the optical conductivity σ(ω) of a slightly doped one-dimensional Mott insulator in a regime where the average distance between charge excitations is large compared to their thermal de Broglie wavelength and a classical description is possible.
Abstract: We study numerically how conservation laws affect the optical conductivity σ(ω) of a slightly doped one-dimensional Mott insulator. We investigate a regime where the average distance between charge excitations is large compared to their thermal de Broglie wavelength and a classical description is possible. Due to conservation laws, the dc conductivity is infinite and the Drude weight D is finite even at finite temperatures. Our numerical results test and confirm exact theoretical predictions for D both for integrable and non-integrable models. Small deviations from integrability induce slowly decaying modes and, consequently, low-frequency peaks in σ(ω), which can be described by a memory matrix approach.
TL;DR: In this paper, the first order metal/non-metal transition and canted antiferromagnetic ordering occur for 0.00 ≤ x ≤ 0.20 ≤ x < 0.15, similar to those in the bandwidth controlled system Ca 2- x Sr x RuO 4 (CSRO).
Abstract: We have grown single crystals of electron doping system Ca 2- x La x RuO 4 (0.00 ≤ x ≤0.20) by a floating zone method. The first order metal/non-metal transition and canted antiferromagnetic ordering occur for 0.00 < x < 0.15, similar to those in the bandwidth controlled system Ca 2- x Sr x RuO 4 (CSRO). However, comparing with CSRO, we found a rather different metallic ground state adjacent to the non-metallic ground state with canted antiferromagnetic order. Instead of short-range antiferromagnetic correlation found in CSRO (0.20 ≤ x < 0.50), the metallic ground state of the present system is characterized by strong ferromagnetic correlation.
01 Jan 2001
TL;DR: In this paper, a scaling theory of the Mott transition was introduced to study the quantum nature of the many-body instability in strongly correlated electronic materials, which can be generally associated with the setting of Fermi-liquid behavior with decreasing temperature in 3D strongly interacting electronic systems.
Abstract: The theory of quantum critical phenomena is introduced to study some current many-body problems in condensed matter physics. Renormalization group concepts are applied to strongly correlated electronic materials which are close to a zero-temperature instability. These systems have enhanced effective masses and susceptibility. Scaling arguments yield the exponents which govern the critical behavior of these quantities in terms of the usual critical exponents associated with a zero-temperature phase transition. We show the existence of a new energy scale, related to the quantum nature of the many-body instability, which can be generally associated with the setting of Fermi-liquid behavior with decreasing temperature in three-dimensional strongly interacting electronic systems. The theory of quantum critical phenomena is used to investigate the Kondo lattice problem, which provides a model to describe heavy-fermion systems and to introduce a scaling theory of the Mott transition with special emphasis on charge fluctuation effects. However, this report is not a review on heavy fermions and Mott insulators. The microscopic theories of these systems are still controversial and present some of the most challenging and instigating problems in condensed matter physics. This state of affairs stimulated the author to review and extend the scaling approach. The scaling theory we develop provides a powerful tool, based on the notion of universality, to understand the physical properties of correlated systems beyond the mean-field level. This is illustrated by our treatment of the one-dimensional Hubbard model, where, although the Fermi-liquid fixed point does not survive the fluctuations, the scaling approach is still useful. Finally, we discuss briefly how disorder affect our results.
TL;DR: In this paper, the critical behavior of a doped Mott insulator near the metal-insulator transition for the infinite-dimensional Hubbard model using a linearized form of dynamical mean-field theory was studied.
Abstract: We have studied the critical behaviour of a doped Mott insulator near the metal-insulator transition for the infinite-dimensional Hubbard model using a linearized form of dynamical mean-field theory The discontinuity in the chemical potential in the change from hole to electron doping, for U larger than a critical value U
c, has been calculated analytically and is found to be in good agreement with the results of numerical methods We have also derived analytic expressions for the compressibility, the quasiparticle weight, the double occupancy and the local spin susceptibility near half-filling as functions of the on-site Coulomb interaction and the doping
Patent•
IBM1
TL;DR: In this article, a method and structure of forming an integrated circuit chip having a transistor includes forming a conductive oxide layer, forming a Mott transition oxide layer over the conductive layer and forming an insulative oxide layer on top of the transition layer.
Abstract: A method and structure of forming an integrated circuit chip having a transistor includes forming a conductive oxide layer, forming a Mott transition oxide layer over the conductive oxide layer and forming an insulative oxide layer over the Mott transition oxide layer.
TL;DR: In this article, it was shown that in a commensurate bosonic ladder, a quantum phase transition occurs between a Mott insulator and a superfluid when interchain hopping increases.
Abstract: We show that in a commensurate bosonic ladder, a quantum phase transition occurs between a Mott insulator and a superfluid when interchain hopping increases. We analyze the properties of this transition as well as the physical properties of the two phases. We discuss the physical consequences for experimental systems such as Josephson Junction arrays.
TL;DR: In this article, the authors studied weakly coupled Hubbard chains in the half-filled case, and showed rigorously how spinon-anti spinon pairs produced an antiferromagnetic interchain exchange of the order of
Abstract: We study two (very) weakly coupled Hubbard chains in the half-filled case, and especially the situation where the intrachain Mott scale m is much larger than the (bare) single-electron interchain hopping ${t}_{\ensuremath{\perp}}.$ First, we find that the divergence of the intrachain umklapp channel at the Mott transition results in the complete vanishing of the single-electron interchain hopping: this is significant of a strong confinement of coherence along the chains. Excitations are usual charge fermionic solitons and spinon-(anti)spinon pairs of the Heisenberg chain. Then, we show rigorously how the tunneling of spinon-(anti)spinon pairs produces an antiferromagnetic interchain exchange of the order of ${J}_{\ensuremath{\perp}}{=t}_{\ensuremath{\perp}}^{2}/m.$ In the ``confined'' phase and in the far infrared, the system behaves as a pure spin ladder. The final result is an insulating ground state with spin-gapped excitations exactly as in the opposite ``delocalized'' limit (i.e., for rather large interchain hoppings) where the two-leg ladder is in the well-known insulating $D\ensuremath{-}\mathrm{Mott}$ phase. Unlike materials with an infinite number of coupled chains (Bechgaard salts), the confinement/deconfinement transition at absolute zero is here a simple crossover: no metallic phase is found in undoped two-leg ladders. This statement might be generalized for N-leg ladders with $N=3,4,\dots{}$ (but not too large).
TL;DR: In this paper, the electronic structure for a modulation doped and gated T-shaped quantum wire using density functional theory was calculated, and the binding energy of excitons in a finite length wire using a simpler, cylindrical geometry.
Abstract: We calculate the electronic structure for a modulation doped and gated T-shaped quantum wire using density functional theory. We calculate the band-gap renormalization as a function of the density of conduction band electrons, induced by the donor layer and/or the gate, for the translationally invariant wire, incorporating all growth and geometric properties of the structure completely. We show that most of the band-gap renormalization arises from exchange-correlation effects, but that a small shift also results from the difference of wave function evolution between electrons and holes. We calculate the binding energy of excitons in a finite length wire using a simpler, cylindrical geometry. For a single hole and a one-dimensional electron gas of density ${n}_{e},$ screening of the exciton binding energy is shown to approximately compensate for band-gap renormalization, suggesting that the recombination energy remains approximately constant with ${n}_{e},$ in agreement with experiment. We find that the nature of screening, as treated within our nonlinear model, is significantly different from that of the various linear screening treatments, and the orthogonality of free carrier states with the bound electron states has a profound effect on the screening charge. In particular, we find no Mott transition. Rather, the electron and hole remain bound for all densities up to $\ensuremath{\sim}3\ifmmode\times\else\texttimes\fi{}{10}^{6}{\mathrm{cm}}^{\ensuremath{-}1}$ and, as ${n}_{e}$ increases from zero, trion and even ``quadron'' formation becomes allowed.
TL;DR: In this paper, the physical properties of pyrochlore ruthenates R 2− x Ca x Ru 2 O 7 (R=Y,Sm) have been studied and it has been shown that upon increasing Ca concentration, or upon increasing holes introduced into the Mott insulating state, the system exhibits a transition to a metallic state.
TL;DR: In this paper, a relativistic three-body equation was proposed to study correlations in a medium of finite temperatures and densities, which includes the dominant medium effects due to Pauli blocking and self energy corrections.
Abstract: We present a relativistic three-body equation to study correlations in a medium of finite temperatures and densities. This equation is derived within a systematic Dyson equation approach and includes the dominant medium effects due to Pauli blocking and self energy corrections. Relativity is implemented utilizing the light front form. The equation is solved for a zero-range force for parameters close to the confinement-deconfinement transition of QCD. We present correlations between two- and three-particle binding energies and calculate the three-body Mott transition.
TL;DR: In this paper, a relativistic three-body equation was proposed to study correlations in a medium of finite temperatures and densities, which includes the dominant medium effects due to Pauli blocking and self energy corrections.
TL;DR: In this article, a many-body hamiltonian that includes intra-and inter-site electron interactions was defined for the surface bands of the Sn/Si(1 1 1 1) surface.
01 Jan 2001
TL;DR: In this article, the basic ideas of the dynamical mean field theory (DMFT) are reviewed and some of the remarkable insights into the electronic structure of strongly correlated electrons are introduced using the simplest model Hamiltonians.
Abstract: We review the basic ideas of the dynamical mean field theory (DMFT). Some of the remarkable insights into the electronic structure of strongly correlated electrons are introduced using the simplest model Hamiltonians. We then discuss the perspectives for carrying out more realistic DMFT studies of strongly correlated electron systems and we compare it with existent methods, LDA and LDA+U. We stress the existence of new functional for electronic structure calculations which allow us to treat situations where the single-particle description breaks down such as the vicinity of the Mott transition.
TL;DR: In this paper, the exact diagonalization of the two-band Hubbard model with infinite dimensions was used to investigate the electronic states in the half-filled case, and the boundary separating the metallic and the insulating regimes was calculated as the function of the on-site repulsive interaction U and the charge-transfer energy Δ.
TL;DR: In this paper, the Mott metal-insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory, and the discontinuity in the chemical potential for the change from hole to electron doping is calculated analytically as a function of the on-site Coulomb interaction U at the d-orbital and the charge-transfer energy Δ between the d - and p -orbitals.
Abstract: The Mott metal–insulator transition in the two-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory. The discontinuity in the chemical potential for the change from hole to electron doping is calculated analytically as a function of the on-site Coulomb interaction U at the d -orbital and the charge-transfer energy Δ between the d - and p -orbitals. Critical behaviour of the quasiparticle weight is also obtained analytically as a function of U and Δ. The analytic results are in good agreement with the numerical results of the exact diagonalization method.