7,360 research outputs found
Metallic and Insulating Adsorbates on Graphene
We directly compare the effect of metallic titanium (Ti) and insulating
titanium dioxide (TiO2) on the transport properties of single layer graphene.
The deposition of Ti results in substantial n-type doping and a reduction of
graphene mobility by charged impurity scattering. Subsequent exposure to oxygen
largely reduces the doping and scattering by converting Ti into TiO2. In
addition, we observe evidence for short-range scattering by TiO2 impurities.
These results illustrate the contrasting scattering mechanisms for identical
spatial distributions of metallic and insulating adsorbates
Zero-temperature Phase Diagram of Two Dimensional Hubbard Model
We investigate the two-dimensional Hubbard model on the triangular lattice
with anisotropic hopping integrals at half filling. By means of a self-energy
functional approach, we discuss how stable the non-magnetic state is against
magnetically ordered states in the system. We present the zero-temperature
phase diagram, where the normal metallic state competes with magnetically
ordered states with and structures. It is shown
that a non-magnetic Mott insulating state is not realized as the ground state,
in the present framework, but as a meta-stable state near the magnetically
ordered phase with structure.Comment: 4 pages, 4 figure
Exact Drude weight for the one-dimensional Hubbard model at finite temperatures
The Drude weight for the one-dimensional Hubbard model is investigated at
finite temperatures by using the Bethe ansatz solution. Evaluating finite-size
corrections to the thermodynamic Bethe ansatz equations, we obtain the formula
for the Drude weight as the response of the system to an external gauge
potential. We perform low-temperature expansions of the Drude weight in the
case of half-filling as well as away from half-filling, which clearly
distinguish the Mott-insulating state from the metallic state.Comment: 9 pages, RevTex, To appear in J. Phys.
Half-Quantum Vortices in Thin Film of Superfluid He
Stability of a half-quantum vortex (HQV) in superfluid He has been
discussed recently by Kawakami, Tsutsumi and Machida in Phys. Rev. B {\bf 79},
092506 (2009). We further extend this work here and consider the A phase of
superfluid He confined in thin slab geometry and analyze the HQV realized
in this setting. Solutions of HQV and singly quantized singular vortex are
evaluated numerically by solving the Ginzburg-Landau (GL) equation and
respective first critical angular velocities are obtained by employing these
solutions. We show that the HQV in the A phase is stable near the boundary
between the A and A phases. It is found that temperature and magnetic
field must be fixed first in the stable region and subsequently the angular
velocity of the system should be increased from zero to a sufficiently large
value to create a HQV with sufficiently large probability. A HQV does not form
if the system starts with a fixed angular velocity and subsequently the
temperature is lowered down to the A phase. It is estimated that the
external magnetic field with strength on the order of 1 T is required to have a
sufficiently large domain in the temperature-magnetic field phase diagram to
have a stable HQV.Comment: 5 pages, 5 figure
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
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
Evaluation of laboratory tests for determining the lethal temperature of Vitis labruscana BAILEY Concord roots exposed to subzero temperatures
The roots of 1-year-old dormant Concord plants were subjected to subzero temperatures in a cold box programmed to lower the temperature at -2 °C/h. Temperatures down to -30 °C with -5 °C decrements and -20 °C with -2 °C decrements were used. Electrical conductivity (EC), triphenyl tetrazolium chloride reduction (TTC), and tissue browning (TB) tests were conducted on roots of 1-3 and 4-6 mm in diameter. Growth and survival tests were also conducted. Based on these tests, the lethal temperature of Concord roots was near -5 °C. The plants exposed to -10 °C grew but subsequently died. Lethal temperature of roots indicated by EC and TTC was comparable to that obtained from the survival test. TB tests, though qualitative, were useful in evaluating root injury to tissues and can be used in conjunction with other tests
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