Mott transition

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

Orbital-selective Mott-Hubbard transition in the two-band Hubbard model

Abstract: Max-Planck-Institut fu¨r Festk¨orperforschung, 70569 Stuttgart, Germany(Dated: October 18, 2005)Recent advances in the field of quantum Monte Carlo simulations for impurity problems allow–within dynamical mean field theory– for a more thorough investigation of the two-band Hubbardmodel with narrow/wide band and SU(2)-symmetric Hund’s exchange. The nature of this transitionhas been controversial, and we establish that an orbital-selective Mott-Hubbard transition exists.Thereby, the wide band still shows metallic behavior after the narrow band became insulating -nota pseudogap as for an Ising Hund’s exchange. The coexistence of two solutions with metallic wideband and insulating or metallic narrow band indicates, in general, first-order transitions.

A surface-tailored, purely electronic, mott metal-to-insulator transition.

Abstract: Mott transitions, which are metal-insulator transitions (MITs) driven by electron-electron interactions, are usually accompanied in bulk by structural phase transitions. In the layered perovskite Ca(1.9)Sr(0.1)RuO4, such a first-order Mott MIT occurs in the bulk at a temperature of 154 kelvin on cooling. In contrast, at the surface, an unusual inherent Mott MIT is observed at 130 kelvin, also on cooling but without a simultaneous lattice distortion. The broken translational symmetry at the surface causes a compressional stress that results in a 150% increase in the buckling of the Ca/Sr-O surface plane as compared to the bulk. The Ca/Sr ions are pulled toward the bulk, which stabilizes a phase more amenable to a Mott insulator ground state than does the bulk structure and also energetically prohibits the structural transition that accompanies the bulk MIT.

Strongly correlated excitonic insulator in atomic double layers

Abstract: Excitonic insulators (EIs) arise from the formation of bound electron–hole pairs (excitons)1,2 in semiconductors and provide a solid-state platform for quantum many-boson physics3–8. Strong exciton–exciton repulsion is expected to stabilize condensed superfluid and crystalline phases by suppressing both density and phase fluctuations8–11. Although spectroscopic signatures of EIs have been reported6,12–14, conclusive evidence for strongly correlated EI states has remained elusive. Here we demonstrate a strongly correlated two-dimensional (2D) EI ground state formed in transition metal dichalcogenide (TMD) semiconductor double layers. A quasi-equilibrium spatially indirect exciton fluid is created when the bias voltage applied between the two electrically isolated TMD layers is tuned to a range that populates bound electron–hole pairs, but not free electrons or holes15–17. Capacitance measurements show that the fluid is exciton-compressible but charge-incompressible—direct thermodynamic evidence of the EI. The fluid is also strongly correlated with a dimensionless exciton coupling constant exceeding 10. We construct an exciton phase diagram that reveals both the Mott transition and interaction-stabilized quasi-condensation. Our experiment paves the path for realizing exotic quantum phases of excitons8, as well as multi-terminal exciton circuitry for applications18–20. So far only signatures of excitonic insulators have been reported, but here direct thermodynamic evidence is provided for a strongly correlated excitonic insulating state in transition metal dichalcogenide semiconductor double layers.

Decay of superfluid currents in a moving system of strongly interacting bosons

Abstract: We analyze the stability and decay of supercurrents of strongly interacting bosons on optical lattices. At the mean-field level, the system undergoes an irreversible dynamic phase transition, whereby the current decays beyond a critical phase gradient that depends on the interaction strength. At commensurate filling the transition line smoothly interpolates between the classical modulational instability of weakly interacting bosons and the equilibrium Mott transition at zero current. Below the mean-field instability, the current can decay due to quantum and thermal phase slips. We derive asymptotic expressions of the decay rate near the critical current. In a three-dimensional optical lattice this leads to very weak broadening of the transition. In one and two dimensions the broadening leads to significant current decay well below the mean-field critical current. We show that the temperature scale below which quantum phase slips dominate the decay of supercurrents is easily within experimental reach.

Two Types of Mott Transitions

Abstract: One type of Mott transition (MT1) is characterized by diverging enhancement of the charge effective mass when one approaches a Mott insulator from the side of the paramagnetic metal. Another fundamentally different type of Mott transition (MT2) is shown to exist when a spin gap opens. The linear coefficient of the specific heat γ decreases and then vanishes at the transition point of MT2 in sharp contrast with MT1. As an example, a dimerized t - J model is shown to undergo MT2. The underlying pairing mechanism determines the character of MT2. Recent controversial experimental results on the Mott transitions in copper oxides and other strongly correlated systems are discussed from the above viewpoint.