Mott transition

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

Correlation effects in a few-particle one-dimensional Coulomb-interacting system

Abstract: A model of the one-dimensional Coulomb-interacting few-particle system is studied in detail. The model is similar to a many-electron system which in a zero-order approximation of the non-interacting particles has only singly occupied one-electron levels. Such model cancels the divergencies in the Coulomb and exchange interaction energies found regularly for a conventional one-dimensional system which is built up of the doubly occupied one-electron levels and is submitted to the Coulomb perturbation. In the present case, the correlated wave functions for the system can be obtained from the Slater determinants constructed for the sets of the one-electron levels and combined according to the rules given by the standard perturbation theory. The calculations allow us to discuss the correlation influence and the effect of the size of the model on: (i) the excitation energies including the criterion corresponding to the metal-insulator transition (the Mott transition), (ii) the distribution of the correlated charge along the model, (iii) the average velocity of a two-particle system being in different states, and (iv) the dipole moments and transition probabilities. In the last case, the lifetime of the uncorrelated and correlated excited states obtained in the situation of the allowed one-photon transitions can be compared with the lifetime obtained for a similar system in the case when the one-photon transitions are forbidden and two-photon transitions should be taken into account. No data other than the length of the model and the fundamental constants of nature enter the calculations.

High-pressure study of a Mott insulator (BEDT-TTF) (TCNQ)

Abstract: The resistive state of the charge-transfer complex, (BEDT-TTF)(TCNQ), was studied by application of hydrostatic pressure and uniaxial strain. An obtained (hydrostatic) pressure-temperature phase diagram was different from a reported one [1]: in our phase diagram, low-temperature metallic phase exists. The results obtained by application of uniaxial strains were discussed in terms of a role of the dimer of BEDT-TTF in the present salt.

Ultrasonic investigation of the P-T phase diagram of κ-(BEDT-TTF)2X organic superconductors

Abstract: Depending on the exact pressure conditions (hydrostatic or chemical by anion X substitution), the normal phase of the κ-(BEDT-TTF) 2 X organic conductors is either a Mott insulator and/or an unconventional metal. Among them, κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl stands as the prototype material since it shows the complete sequence of states within a pressure interval of a few hundreds bars. Ultrasonic waves constitute excellent tools to probe such electronic states but experiments on organics are scarce due their brittleness and very small dimensions. We present a recent ultrasonic study of a few κ-(BEDT-TTF) 2 X organic compounds under hydrostatic pressure conditions. Different phase transitions are identified trough several elastic anomalies characterized from isobaric and isothermal sweeps. Beyond the confirmation of the P-T diagram of a typical Mott material, our ultrasonic data on the κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl conductor allows a detailed study of the critical point region. The very large softening of the velocity at the critical point corresponds to the predicted compressibility divergence of the electronic degrees of freedom and validates then, the DMFT picture of the Mott transition. Most importantly, our data reveal that the high pressure crossover line coincides with the pseudogap features previously observed in magnetic and transport properties. Impurity and crystal quality effects on the phase diagram will also be discussed.

Disorder-induced Missing Moment of Inertia in Solid $^4$He

Abstract: A microscopic model for the experimentally observed missing moment of inertia in the torsional oscillator experiments on partially-annealed solid $^4$He is proposed. We argue that an ordered array of $^4$He atoms is a Mott insulator. Disorder destroys the Mott state producing localized states in the gap which beyond a critical value of the disorder induce a superfluid state. Depending on the magnitude of the disorder, we find that the destruction of the superfluid takes place either through a Bose glass phase (strong disorder) or through a direct transition to the Mott insulator (weak disorder). The critical value of the disorder that separates the weak and strong regimes is shown to be a decreasing function of the boson filling. Consequently, bosonic systems at large fillings are always in the strong disorder regime and the Bose glass always surrounds the Mott lobes, thereby settling an unresolved controversy in this field. We apply our work to the experimentally observed enhancement $^3$He impurities has on the onset temperature for the missing moment of inertia. We find quantitative agreement with experimental trends.