Mott Insulator Regime Research Articles

Vortex Structures in a Chain of Coupled Bosonic Wells and the Mott Regime

We describe a system of coupled bosonic wells by means of the Bose-Hubbard model. Its dynamics is investigated via the time-dependent variational principle and coherent states. Some exact solutions of the dynamics, which have a vortex-like structure, are explicitly found, and used together with semiclassical requantization to describe the dynamics in the Mott insulator regime.

Magnetic Properties of TTF-Type Charge Transfer Salts in the Mott Insulator Regime

Abstract We have investigated the magnetic properties of several TTF-based Mott insulators consisting of dimerized/trimerized-donor units, which are classified into three subgroups: (1) β′-(BEDT-TTF)2X (X = ICl2, AuCl2) and (BEDT-TTF)2GaCl4 as strong dimer systems, (2) α′-(BEDT-TTF)2IBr2 salt as a weak dimer system, and (3) (BMDT-TTF)3ClO4(1,2-dichloroethane) and (BMDT-TTF)3AsF6(1,1,2-trichloroethane) as weak trimer systems. The group (1) compounds have localized spin systems with an S = 1/2 localized spin per dimer unit. In group (2), weak dimerization produces a fractional magnetic moment, which reflects the delocalization of the electrons, although the magnetism is described in terms of an S = 1/2 low-dimensional antiferromagnet. The ClO4 salt in the group (3) indicates the existence of a localized spin per trimer, whereas the trimerization is quite weak, because the inter-trimer Coulomb interactions generate the charge disproportionation resulting in the localization of electrons. The absence of the charge disproportionation brings about the feature of fractional magnetic moments in the AsF6 salts.

Vortex plastic flow, local flux density, magnetization hysteresis loops, and critical current, deep in the Bose-glass and Mott-insulator regimes.

We present simulations of flux-gradient-driven superconducting vortices interacting with strong columnar pinning defects as an external field $H(t)$ is quasi-statically swept from zero through a matching field $B_{\phi}$. We analyze several measurable quantities, including the local flux density $ B(x,y,H(t))$, magnetization $M(H(t))$, critical current $J_{c}(B(t))$, and the individual vortex flow paths. We find a significant change in the behavior of these quantities as the local flux density crosses $B_{\phi}$, and quantify it for many microscopic pinning parameters. Further, we find that for a given pin density $J_c(B)$ can be enhanced by maximizing the distance between the pins for $ B < B_{\phi} $.