Mott transition

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

Microscopic origin of metal-to-insulator transition in tightly-coupled metamaterials

Abstract: We present a microscopic origin of metal-to-insulator transition (MIT) in tightly-coupled metamaterials. Like Mott transition in crystal solid, MIT in metamaterial is shown to arise when the distance between unit resonators passes the critical gap-size.

Bound-state transition: an analytical model

Abstract: By using an accurate dielectric function for a homogeneous paramagnetic electron liquid we attempt a simple analytical treatment of the bound-state (metal-insulator) transition in a system consisting of a single proton immersed in the electron liquid, as a function of global density. The inability of the resulting effective Thomas-Fermi picture to account for the transition is remedied by the inclusion of the appropriate cusp condition that is also introduced in a simple analytical manner. The expected transition from a delocalized state (at high density) to a localized state (at low density) is shown to be the result of the combined action of a minimal number of very general principles such as overall charge neutrality, the compressibility sum rule and the so-called q 4 sum rule, at the simplest analytical level.

FLEX Study on Two-Dimensional t-t -Hubbard Model: Enhanced Charge Susceptibility near Antiferromagnetic Mott Transition

Abstract: Since the two-dimensional (2D) Hubbard model is one of the simplest model having features of layered cuprates which is widely known as high-Tc superconductor, many researchers pay their attention to this model. One of the purposes of this thesis is to discuss, on the basis of the fluctuation exchange (FLEX) approximation which satisfies the conservation law and takes account of the spin fluctuations, how the shape of the Fermi surface (FS) is modified and how the charge susceptibility behaves in the 2D t−t′−U Hubbard model near half filling as strength of the onsite Coulomb interaction U is increased. The antiferromagnetic (AF) correlation length is shown to be enhanced as the Coulomb interaction get closer to the critical value Uc for the critical point to onset AF order. At the same time, the shape of the renormalized FS is deformed showing the tendency of nesting and the charge susceptibility shows a pronounced enhancement near Uc. This result is consistent with experimental observations in under-doped cuprates LSCO. The enhancement of the charge susceptibility is so large that it cannot be explained by the van Hove singularity of the density of states (DOS) due to the nesting of FS. Indeed, the van Hove singularity of DOS is easily cancelled by the RPA type contribution. Another purpose of this thesis is to investigate an origin of the divergent charge susceptibility. It is expected that the effect of the AF spin fluctuations is the main origin for this divergence of the charge susceptibility from the fact that the anomaly is observed near the antiferromagnetic insulating (AFI) phase. In order to verify this physical picture, we calculate the Aslamasov-Larkin (AL) type contribution to the charge susceptibility, and compare its value with that calculated by the FLEX approximation. The result is that the AL-type contribution nearly exhaust the value of the enhanced charge susceptibility where the charge susceptibility is enhanced enough as

Quantum Chemistry and Superconductors

Abstract: Thirty years after the discovery of high temperature (HT) superconductivity (SC), no by all accepted theory exists. The Bardeen, Cooper, Schrieffer (BCS) model, hewed into the Bloch theory for metals, is unfit for local systems such as cuprates and organic superconductors. In this chapter, we will use a theory that dates back to Landau and Pekar, but we will avoid the effective mass approach by using a total free energy model, as designed for electron transfer problems by Marcus and Jortner. A diffusion equation is used to derive the resistivity in the local case. The original definition of Hubbard U by Mott as a metal-to-metal (or molecule-to-molecule) charge transfer energy will be updated by including the neglected negative terms. It will be shown that the absorption at 2 eV in the cuprates is indeed due to Cu–Cu charge transfer, identical to the Hubbard U or Mott transition. The model accounts for bond-length fluctuations due to occupancy of d-orbitals (extended over the ligands), or in the molecular case the π orbitals, and this makes it necessary to make a distinction between adiabatic and vertical Hubbard U . U vert = 1.5–3 eV while U ad may be a few hundred times smaller. Organic SC in aromatic hydrocarbons will be shortly reviewed and found consistent with the general model. Finally, we will discuss SC in tungsten bronzes discovered in 1964 by Matthias.

Almost localized fermions in a magnetic field deviation from the Landau picture and a transition to non-Fermi liquid

Abstract: We discuss physical properties of almost localized fermions originating from the spin-dependent effective masses, and a nonlinear molecular field , as well as propose a transition to a non-Fermi liquid at a critical (metamagnetic) field. These features explain in a coherent manner the observed behavior of the CeRu 2 Si 2 system, regarded as a system of heavy quasiparticles close to the Mott localization.