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Mott Insulator (mott + insulator)
Selected AbstractsElectric-Field-Assisted Nanostructuring of a Mott InsulatorADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Vincent Dubost Abstract Here, the first experimental evidence for a strong electromechanical coupling in the Mott insulator GaTa4Se8 that allows highly reproducible nanoscaled writing by means of scanning tunneling microscopy (STM) is reported. The local electric field across the STM junction is observed to have a threshold value above which the clean (100) surface of GaTa4Se8 becomes mechanically instable: at voltage biases >1.1,V, the surface suddenly inflates and comes in contact with the STM tip, resulting in nanometer-sized craters. The formed pattern can be indestructibly "read" by STM at a lower voltage bias, thus allowing 5,Tdots inch,2 dense writing/reading at room temperature. The discovery of the electromechanical coupling in GaTa4Se8 might give new clues in the understanding of the electric pulse induced resistive switching recently observed in this stoichiometric Mott insulator. [source] Interacting bosons in an optical latticeANNALEN DER PHYSIK, Issue 8 2008C. Moseley Abstract A strongly interacting Bose gas in an optical lattice is studied using a hard-core interaction. Two different approaches are introduced, one is based on a spin-1/2 Fermi gas with attractive interaction, the other one on a functional integral with an additional constraint (slave-boson approach). The relation between fermions and hard-core bosons is briefly discussed for the case of a one-dimensional Bose gas. For a three-dimensional gas we identify the order parameter of the Bose-Einstein condensate through a Hubbard-Stratonovich transformation and treat the corresponding theories within a mean-field approximation and with Gaussian fluctuations. This allows us to evaluate the phase diagram, including the Bose-Einstein condensate and the Mott insulator, the density-density correlation function, the static structure factor, and the quasiparticle excitation spectrum. The role of quantum and thermal fluctuations are studied in detail for both approaches, where we find good agreement with the Gross-Pitaevskii equation and with the Bogoliubov approach in the dilute regime. In the dense regime, which is characterized by the phase transition between the Bose-Einstein condensate and the Mott insulator, we discuss a renormalized Gross-Pitaevskii equation. This equation can describe the macroscopic wave function of the Bose-Einstein condensate in the dilute regime as well as close to the transition to the Mott insulator. Finally, we compare the results of the attractive spin-1/2 Fermi gas and those of the slave-boson approach and find good agreement for all physical quantities. [source] Stripe fractionalization: the quantum spin nematic and the Abrikosov latticePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003J. Zaanen The cover picture of physica status solidi (b), taken from the Editor's Choice of this issue, shows a scheme of construction of the spin nematic ordered state and the topological interaction between spatially disconnected gauge defects. The gauge symmetry is broken by applying an external field B. The theory described in the paper [1] offers a potential explanation for recent observations of magnetic field induced antiferromagnetism in La1.9Sr0.1CuO4. The first author, Jan Zaanen, is Professor of Physics at the Instituut-Lorentz in Leiden where he works on quantum field theory in condensed matter physics, concentrating on problems in high- TC superconductivity, quantum magnetism, quantum liquid crystals, doped Mott insulators, and strongly correlated electron systems. This paper is an invited presentation from the European Conference Physics of Magnetism (PM'02), held in Pozna,, Poland, 1,5 July 2002. The proceedings of this conference are published in two parts: in the present issue of phys. stat. sol. (b) and in phys. stat. sol. (a) 196, No. 1 (2003). [source] | ||||||||||