4,756 research outputs found
On Models with Inverse-Square Exchange
A one-dimensional quantum N-body system of either fermions or bosons with
colors interacting via inverse-square exchange is presented in this
article. A class of eigenstates of both the continuum and lattice version of
the model Hamiltonians is constructed in terms of the Jastrow-product type wave
function. The class of states we construct in this paper corresponds to the
ground state and the low energy excitations of the model that can be described
by the effective harmonic fluid Hamiltonian. By expanding the energy about the
ground state we find the harmonic fluid parameters (i.e. the charge, spin
velocities, etc.), explicitly. The correlation exponent and the compressibility
of are also found. As expected the general harmonic relation(i.e.
) is satisfied among the charge and spin velocities.Comment: 26 page
Majorana bound state in rotating superfluid 3He-A between parallel plates
A concrete and experimentally feasible example for testing the putative
Majorana zero energy state bound in a vortex is theoretically proposed for a
parallel plate geometry of superfluid He-A phase. We examine the
experimental setup in connection with ongoing rotating cryostat experiments.
The theoretical analysis is based on the well-established Ginzburg--Landau
functional, supplemented by microscopic calculations of the Bogoliubov--de
Gennes equation, both of which allow the precise location of the parameter
regions of the Majorana state to be found in realistic situations.Comment: 5 pages, 4 figure
Solutions to the Multi-Component 1/R Hubbard Model
In this work we introduce one dimensional multi-component Hubbard model of
1/r hopping and U on-site energy. The wavefunctions, the spectrum and the
thermodynamics are studied for this model in the strong interaction limit
. In this limit, the system is a special example of Luttinger
liquids, exhibiting spin-charge separation in the full Hilbert space.
Speculations on the physical properties of the model at finite on-site energy
are also discussed.Comment: 9 pages, revtex, Princeton-May1
Exact results for SU(3) spin chains: trimer states, valence bond solids, and their parent Hamiltonians
We introduce several exact models for SU(3) spin chains: (1) a
translationally invariant parent Hamiltonian involving four-site interactions
for the trimer chain, with a three-fold degenerate ground state. We provide
numerical evidence that the elementary excitations of this model transform
under representation 3bar of SU(3) if the original spins of the model transform
under rep. 3. (2) a family of parent Hamiltonians for valence bond solids of
SU(3) chains with spin reps. 6, 10, and 8 on each lattice site. We argue that
of these three models, only the latter two exhibit spinon confinement and a
Haldane gap in the excitation spectrum
Magnetic Moment Formation in Graphene Detected by Scattering of Pure Spin Currents
Hydrogen adatoms are shown to generate magnetic moments inside single layer
graphene. Spin transport measurements on graphene spin valves exhibit a dip in
the non-local spin signal as a function of applied magnetic field, which is due
to scattering (relaxation) of pure spin currents by exchange coupling to the
magnetic moments. Furthermore, Hanle spin precession measurements indicate the
presence of an exchange field generated by the magnetic moments. The entire
experiment including spin transport is performed in an ultrahigh vacuum
chamber, and the characteristic signatures of magnetic moment formation appear
only after hydrogen adatoms are introduced. Lattice vacancies also demonstrate
similar behavior indicating that the magnetic moment formation originates from
pz-orbital defects.Comment: accepted to Phys. Rev. Let
Second Harmonic Coherent Driving of a Spin Qubit in a Si/SiGe Quantum Dot
We demonstrate coherent driving of a single electron spin using second
harmonic excitation in a Si/SiGe quantum dot. Our estimates suggest that the
anharmonic dot confining potential combined with a gradient in the transverse
magnetic field dominates the second harmonic response. As expected, the Rabi
frequency depends quadratically on the driving amplitude and the periodicity
with respect to the phase of the drive is twice that of the fundamental
harmonic. The maximum Rabi frequency observed for the second harmonic is just a
factor of two lower than that achieved for the first harmonic when driving at
the same power. Combined with the lower demands on microwave circuitry when
operating at half the qubit frequency, these observations indicate that second
harmonic driving can be a useful technique for future quantum computation
architectures.Comment: 9 pages, 9 figure
Optical Conductivity of the Two-Dimensional Hubbard Model
Charge dynamics of the two-dimensional Hubbard model is investigated.
Lanczs-diagonalization results for the optical conductivity and
the Drude weight of this model are presented. Near the Mott transition, large
incoherence below the upper-Hubbard band is obtained together with a remarkably
suppressed Drude weight in two dimensions while the clearly coherent character
is shown in one dimension. The two-dimensional results are consistent with
previous results from quantum Monte Carlo calculations indicating that the Mott
transition in this two-dimensional model belongs to the universality class
characterized by the dynamical exponent of .Comment: 4 pages LaTeX including 2 PS figures, to appear in J. Phys. Soc. Jp
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General treatment of isocurvature perturbations and non-Gaussianities
We present a general formalism that provides a systematic computation of the
linear and non-linear perturbations for an arbitrary number of cosmological
fluids in the early Universe going through various transitions, in particular
the decay of some species (such as a curvaton or a modulus). Using this
formalism, we revisit the question of isocurvature non-Gaussianities in the
mixed inflaton-curvaton scenario and show that one can obtain significant
non-Gaussianities dominated by the isocurvature mode while satisfying the
present constraints on the isocurvature contribution in the observed power
spectrum. We also study two-curvaton scenarios, taking into account the
production of dark matter, and investigate in which cases significant
non-Gaussianities can be produced.Comment: Substantial improvements with respect to the first version. In
particular, we added a discussion on the confrontation of the models with
future observational data. This version is accepted for publication in JCA
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