We consider here a 1D tight-binding model with two uncorrelated random site energies ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{a}}$ and ${\mathrm{\ensuremath{\epsilon}}}_{\mathit{b}}$ constant nearest-neighbor matrix element V. show that if one (or both) of the is assigned at to pairs lattice sites (that is, in succession), an initially localized particle can become delocalized. Its mean-square displacement long times shown grow time as ${\mathit{t}}^{3/2}$ provided...

We devise a model to explain why twisted bilayer graphene exhibits insulating behavior when ν = 2 or 3 charges occupy unit moiré cell, feature attributed Mottness per previous work but not for 1, clearly inconsistent with Mott insulation. compute rs EU/ EK, where EU and EK are the potential kinetic energies, respectively, show that (i) criterion lies at density larger than experimental values by factor of 104 (ii) transition series Wigner crystalline states exists as function ν. find that,...

A widely held view in solid-state physics is that disorder precludes the presence of long-range transport one dimension. series models has been recently proposed do not conform to this view. The primary model random dimer model, which site energies for pairs lattice sites along a linear chain are assigned two values at random. This set conducting states ultimately allow an initially localized particle move through almost ballistically. applicable insulator-metal transition wide class...

We attribute the structural phase transition (SPT) in parent compounds of iron pnictides to orbital ordering. Due anisotropy $d_{xz}$ and $d_{yz}$ orbitals $xy$ plane, a ferro-orbital ordering makes orthorhombic structure more energetically favorable, thus inducing SPT. In this orbital-ordered system, sites with that do not order have higher energies. Scattering itinerant electrons by these localized two-level systems causes resistivity anomaly upon onset The proposed also leads stripe-like...

We consider here a single randomly protonated strand of the conducting polymer polyaniline and show explicitly that disorder inherent in this system is described by random-dimer model Dunlap, Wu, Phillips [Phys. Rev. Lett. 65, 88 (1990)] with off-diagonal disorder. demonstrate exactly location energy band unscattered or states coincides recent calculations Fermi level form polymer. argue then capable explaining insulator-metal transition polyaniline.

The magnetic excitations of the iron pnictides are explained within a degenerate double-exchange model. local-moment spins coupled by superexchanges ${J}_{1}$ and ${J}_{2}$ between nearest next-nearest neighbors, respectively, interact with itinerant electrons ${d}_{xz}$ ${d}_{yz}$ orbitals via ferromagnetic Hund exchange. latter stabilizes $(\ensuremath{\pi},0)$ stripe antiferromagnetism due to emergent ferro-orbital order resulting kinetic-energy gain hopping preferably along spin...

High-temperature superconductivity in the copper-oxide ceramics remains an unsolved problem because we do not know what propagating degrees of freedom are normal state. As a result, weakly interacting which pair up to form superconducting condensate. That electrons cuprates is seen most directly from experiments that show spectral weight redistributions over all energy scales. In correct low-energy theory, such rearrangements minimized. This review focuses on range experimental consequences...

Recent experiments on the twisted transition metal dichalcogenide (TMD) material, $\rm WSe_2/WS_2$, have observed insulating states at fractional occupancy of moir\'e bands. Such were conceived as generalized Wigner crystals (GWCs). In this article, we investigate problem crystallization in presence an underlying (moir\'e) lattice. Based best estimates system parameters, find a variety homobilayer and heterobilayer TMDs to be excellent candidates for realizing GWCs. particular, our analysis...

While the recent advances in topology have led to a classification scheme for electronic bands described by standard theory of metals, similar has not emerged strongly correlated systems such as Mott insulators which partially filled band carries no current. By including interactions topologically non-trivial Haldane model, we show that quarter-filled state emerges with non-zero Chern number provided are sufficiently large. We first motivate this result on physical grounds and then two...

When zeros appear in the Green's function, as strongly correlated systems, invariant ${N}_{3}$ for two-dimensional quantum anomalous Hall insulator does not necessarily encode a topological of ground state, contrast to expectations.

In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin effects. Here we show using determinantal Monte Carlo an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A Mott insulator is underlying cause. The peak in susceptibility consistent with a possible ferromagnetic state T = 0. onset of such magnetism would convert effect. While symmetry-broken...

The conventional theory of metals is in crisis. In the past 15 years, there has been an unexpected sprouting metallic states low-dimensional systems, directly contradicting wisdom. For example, bosons are thought to exist one two ground states: condensed a superconductor or localized insulator. However, several experiments on thin metal-alloy films have observed that phase disrupts direct transition between and We analyze insulator-superconductor argue intervening bosonic. All relevant...

We show that the combined effects of spin orbit, monoclinic distortion, and p-d hybridization in tetrahedrally coordinated Fe LaFeAsO invalidate naive Hund's rule filling d levels. The two highest occupied levels have one electron each, but, as a result differing hybridizations, upper level is more itinerant, while electrons lower are localized. resulting magnetic moment highly anisotropic with an in-plane value 0.25 micro_B-0.35 micro_B per z projection 0.06 micro_B, both which agreement experiment.

In the fermionic sector of top-down approaches to holographic systems, one generically finds that fermions are coupled gravity and gauge fields in a variety ways, beyond minimal coupling. this paper, we take such interaction -- Pauli, or dipole, study its effects on fermion correlators. We find modifies spectral density remarkable way. As change strength interaction, weight is transferred between bands, critical value, hard gap emerges states. A possible interpretation bulk then it drives...

Recent experimental developments in the iron pnictides have unambiguously demonstrated existence of in-plane electronic anisotropy absence long-range magnetic order. Such can arise from orbital ordering, which is described by an energy splitting between two otherwise degenerate ${d}_{xz}$ and ${d}_{yz}$ orbitals. By including this phenomenological order into a five-orbital Hubbard model, we obtain mean-field solutions where determined self-consistently. Despite sensitivity resulting states...

We study the properties of fermion correlators in a boundary theory dual to Reissner-Nordstr\"om ${\mathrm{AdS}}_{d+1}$ background presence bulk dipole (Pauli) interaction term with strength $p$. show that by simply changing value parameter $p$ we can tune continuously from Fermi liquid (small $p$), marginal-Fermi behavior at critical $p$, generic non-Fermi intermediate values and finally Mott insulator large Pauli coupling. As all these phases are seen cuprate phase diagram, holographic...

The characteristic excitation of a metal is its plasmon, which quantized collective oscillation electron density. In 1956, David Pines predicted that distinct type dubbed 'demon', could exist in three-dimensional (3D) metals containing more than one species charge carrier1. Consisting out-of-phase movement electrons different bands, demons are acoustic, electrically neutral and do not couple to light, so have never been detected an equilibrium, 3D metal. Nevertheless, believed be critical...

We present here a granular-rod model for the metallic state of conducting polymer, polyaniline. In this islands correspond to single strands polymer. The macroscopic conductivity results from anisotropic three-dimensional variable-range hopping in network rods. incorporate experimentally observed temperature dependence charge carrier density and show that is capable explaining (1) \ensuremath{\sigma}=${\mathrm{\ensuremath{\sigma}}}_{0}$exp[-(${\mathit{T}}_{0}$/T${)}^{1/2}$], (2) doping...

We show in this paper, within the context of a tight-binding model, that when defects spanning more than one lattice size contain plane symmetry, standard tendency disorder to localize electronic states can be suppressed at certain energies band. A general transfer-matrix approach is used exactly such are sprinkled random on linear chain, \ensuremath{\surd}N (N number states) will remain unscattered by regardless concentration defects. The location energy band determined unit transmission...