Search results for "Coupling"
showing 10 items of 1862 documents
Dielectric and electro-optical studies of a ferroelectric copolysiloxane.
1994
This paper reports an extensive study of the static (spontaneous polarization, ${\mathit{P}}_{\mathit{s}}$, tilt angle \ensuremath{\theta}, and pitch) and dynamic properties of a ferroelectric liquid-crystalline polymer. It is shown that a ferroelectric liquid-crystalline polymer (diluted polysiloxane) exhibits physical behavior similar to that of a low-molar-mass liquid crystal in terms of contrast ratio, pitch of the helix, and relationship between ${\mathit{P}}_{\mathit{s}}$ and \ensuremath{\theta}. The degenerated collective modes for the director rotation are shown to split into two modes at the Sm-A--Sm-${\mathit{C}}^{\mathrm{*}}$ phase transition temperature using dielectric spectros…
Defect states and excitations in a Mott insulator with orbital degrees of freedom: Mott-Hubbard gap versus optical and transport gaps in doped systems
2013
We address the role played by charged defects in doped Mott insulators with active orbital degrees of freedom. It is observed that defects feature a rather complex and rich physics, which is well captured by a degenerate Hubbard model extended by terms that describe crystal-field splittings and orbital-lattice coupling, as well as by terms generated by defects such as the Coulomb potential terms that act both on doped holes and on electrons within occupied orbitals at undoped sites. We show that the multiplet structure of the excited states generated in such systems by strong electron interactions is well described within the unrestricted Hartree-Fock approximation, once the symmetry breaki…
Exact solution of the 1D Hubbard model in the atomic limit with inter-site magnetic coupling
2012
In this paper we present for the first time the exact solution in the narrow-band limit of the 1D extended Hubbard model with nearest-neighbour spin-spin interactions described by an exchange constant J. An external magnetic field h is also taken into account. This result has been obtained in the framework of the Green's functions formalism, using the Composite Operator Method. By means of this theoretical background, we have studied some relevant features such as double occupancy, magnetization, spin-spin and charge-charge correlation functions and derived a phase diagram for both ferro (J>0) and anti-ferro (J<0) coupling in the limit of zero temperature. We also report a study on de…
Viability of Strongly Coupled Scenarios with a Light Higgs-like Boson
2013
We present a one-loop calculation of the oblique S and T parameters within strongly coupled models of electroweak symmetry breaking with a light Higgs-like boson. We use a general effective Lagrangian, implementing the chiral symmetry breaking SU(2)(L) circle times SU(2)(R) -> SU(2)(L+R) with Goldstone bosons, gauge bosons, the Higgs-like scalar, and one multiplet of vector and axial-vector massive resonance states. Using a dispersive representation and imposing a proper ultraviolet behavior, we obtain S and T at the next-to-leading order in terms of a few resonance parameters. The experimentally allowed range forces the vector and axial-vector states to be heavy, with masses above the TeV …
Magnetic properties of smooth terminating dipole bands in 110,112Te
2006
Three strongly coupled sequences have been established in Te-110,Te-112 up to high spins. They are interpreted in terms of deformed structures built on proton 1-particle-1-hole excitations that reach termination at I similar to 40h. This is the first observation of smooth terminating dipole structures in this mass region. Lifetime measurements have allowed the extraction of experimental B(M 1; 1 -> I - 1) and B(E2; I -> I - 2) reduced transition rates for one of the dipole bands in Te-110. The results support the deformed interpretation. (c) 2006 Elsevier B.V. All rights reserved.
Structure of rotational bands in 253No
2009
In-beam gamma-ray and conversion electron spectroscopic studies have been performed on the 253 No nucleus. A strongly coupled rotational band has been identified and the improved statistics allows an assignment of the band structure as built on the $\ensuremath 9/2^-[734]_{\nu}$ ground state. The results agree with previously known transition energies but disagree with the tentative structural assignments made in earlier work.
Critical behaviour in one dimension: unconventional pairing, phase separation, BEC-BCS crossover and magnetic Lifshitz transition
2017
We study the superconducting properties of population-imbalanced ultracold Fermi mixtures in one-dimensional (1D) optical lattices that can be effectively described by the spin-imbalanced attractive Hubbard model (AHM) in the presence of a Zeeman magnetic field. We use the mean-field theory approach to obtain the ground state phase diagrams including some unconventional superconducting phases such as the Fulde--Ferrell--Larkin--Ovchinnikov (FFLO) phase, and the $\eta$ phase (an extremal case of the FFLO phase), both for the case of a fixed chemical potential and for a fixed number of particles. It allows to determine optimal regimes for the FFLO phase as well as $\eta$-pairing stability. We…
Zero-bias conductance peak in detached flakes of superconducting 2H-TaS2probed by scanning tunneling spectroscopy
2014
We report an anomalous tunneling conductance with a zero-bias peak in flakes of superconducting 2$H$-${\mathrm{TaS}}_{2}$ detached through mechanical exfoliation. To explain the observed phenomenon, we construct a minimal model for a single unit cell layer of superconducting 2$H$-${\mathrm{TaS}}_{2}$ with a simplified two-dimensional Fermi surface and a sign-changing Cooper-pair wave function induced by Coulomb repulsion. Superconductivity is induced in the central $\ensuremath{\Gamma}$ pocket, where it becomes nodal. We show that weak scattering at the nodal Fermi surface, produced by nonperturbative coupling between tip and sample, gives Andreev states that lead to a zero-bias peak in the…
Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure
2010
The temperature and pressure dependence of the partial density of phonon states (phonon-DOS) of iron atoms in superconducting ${\text{Fe}}_{1.01}\text{Se}$ was studied by $^{57}\text{F}\text{e}$ nuclear inelastic scattering. The high-energy resolution allows for a detailed observation of spectral properties. A sharpening of the optical phonon modes and shift of all spectral features toward higher energies by $\ensuremath{\sim}4\mathrm{%}$ with decreasing temperature from 296 to 10 K was found. However, no detectable change at the tetragonal--orthorhombic phase transition around 100 K was observed. Application of a pressure of 6.7 GPa, connected with an increase in the superconducting temper…
Radiative lifetimes of the(1–3)Π1states in NaCs: Experiment and theory
2007
The radiative lifetimes of the $(3)\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}$ and $D(2)\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}$ states of the NaCs molecule have been directly measured in a thermal cell from fluorescence kinetics after modulated laser excitation. The experimental ${\ensuremath{\tau}}_{(3)\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}}^{\mathrm{rad}}$ values of the $(3)\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Pi}({v}^{\ensuremath{'}}∊[3,25];{J}^{\ensuremath{'}}∊[25,106])$ levels decrease from $29\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}21\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$ as the ${v}^{\ensuremath{'}}$ values increase. The measured …