Mott transition

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

Effects of Disorder on the Pressure-Induced Mott Transition in $\kappa$-BEDT-TTF)$_2$Cu[N(CN)$_2$]Cl

Abstract: We present a study of the influence of disorder on the Mott metal-insulator transition for the organic charge-transfer salt $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Cl. To this end, disorder was introduced into the system in a controlled way by exposing the single crystals to x-ray irradiation. The crystals were then fine-tuned across the Mott transition by the application of continuously controllable He-gas pressure at low temperatures. Measurements of the thermal expansion and resistance show that the first-order character of the Mott transition prevails for low irradiation doses achieved by irradiation times up to 100 h. For these crystals with a moderate degree of disorder, we find a first-order transition line which ends in a second-order critical endpoint, akin to the pristine crystals. Compared to the latter, however, we observe a significant reduction of both, the critical pressure $p_c$ and the critical temperature $T_c$. This result is consistent with the theoretically-predicted formation of a soft Coulomb gap in the presence of strong correlations and small disorder. Furthermore, we demonstrate, similar to the observation for the pristine sample, that the Mott transition after 50 h of irradiation is accompanied by sizable lattice effects, the critical behavior of which can be well described by mean-field theory. Our results demonstrate that the character of the Mott transition remains essentially unchanged at a low disorder level. However, after an irradiation time of 150 h, no clear signatures of a discontinuous metal-insulator transition could be revealed anymore. These results suggest that, above a certain disorder level, the metal-insulator transition becomes a smeared first-order transition with some residual hysteresis.

Mott transition with holographic spectral function

Abstract: We show that the Mott transition can be realized in a holographic model of a fermion with bulk mass, m, and a dipole interaction of coupling strength p. The phase diagram contains gapless, pseudo-gap and gapped phases and the first one can be further divided into four sub-classes. We compare the spectral densities of our holographic model with the Dynamical Mean Field Theory (DMFT) results for Hubbard model as well as the experimental data of Vanadium Oxide materials. Interestingly, single-site and cluster DMFT results of Hubbard model share some similarities with the holographic model of different parameters, although the spectral functions are quite different due to the asymmetry in the holography part. The theory can fit the X-ray absorption spectrum (XAS) data quite well, but once the theory parameters are fixed with the former it can fit the photoelectric emission spectrum (PES) data only if we symmetrize the spectral function.

Spin and charge dynamics of stripes in doped Mott insulators

Abstract: We study spin and charge dynamics of stripes in doped Mott insulators by considering a two-dimensional Hubbard model with N fermion flavors. For N = 2 we recover the normal one-band model while for N → ∞ a spin density wave mean-field solution. For all band fillings, lattice topologies and N = 4n, the model may be solved by means of quantum Monte Carlo methods without encountering the sign problem. At N = 4 and in the vicinity of the Mott insulator we find a stripe phase. This phase has a quasiparticle gap but conducts due to long-wavelength low-lying collective charge modes.

Electronic Structure of Ion‐Radical Organic Solids and Polyenes

Abstract: The electronic structures of organic ion-radical salts, molecular conductors, and charge-transfer complexes are described by solid-state models with one valence state per site. Similar models occur in π-electron theories of conjugated molecules or in spin Hamiltonians for magnetic insulators. A localized or valence bond (VB) representation is qualitatively adequate in narrow band systems. Diagrammatic VB methods in finite models yield convenient exact solutions to the resulting configuration interaction (CI) problem as correlated states based on linear combinations of VB diagrams. Also found are exact charges, bond orders, ionicity, correlation functions, transition moments or other properties of correlated electronic states. Particular attention is given to qualitative failures of conventional one-electron descriptions, which often reflect degeneracies lifted by correlations. Correlated states give the correct ordering of the 21Ag and 11Bu states of trans-trans octatetraene, clarify the midgap absorption in polyacetylene, rationalize the partial ionicity and electrostatic energy of ion-radical organic complexes, demonstrate an exactly soluble magnetic analog to the Mott transition, and quantitatively fit the thermodynamics of several random-exchange Heisenberg antiferromagnets. Correlated states remain central in simultaneously modeling optical, magnetic, and electrical excitations in π-radical solids.