97,783 research outputs found
Local density of states of electron-crystal phases in graphene in the quantum Hall regime
We calculate, within a self-consistent Hartree-Fock approximation, the local
density of states for different electron crystals in graphene subject to a
strong magnetic field. We investigate both the Wigner crystal and bubble
crystals with M_e electrons per lattice site. The total density of states
consists of several pronounced peaks, the number of which in the negative
energy range coincides with the number of electrons M_e per lattice site, as
for the case of electron-solid phases in the conventional two-dimensional
electron gas. Analyzing the local density of states at the peak energies, we
find particular scaling properties of the density patterns if one fixes the
ratio nu_N/M_e between the filling factor nu_N of the last partially filled
Landau level and the number of electrons per bubble. Although the total density
profile depends explicitly on M_e, the local density of states of the lowest
peaks turns out to be identical regardless the number of electrons M_e. Whereas
these electron-solid phases are reminiscent to those expected in the
conventional two-dimensional electron gas in GaAs heterostructures in the
quantum Hall regime, the local density of states and the scaling relations we
highlight in this paper may be, in graphene, directly measured by spectroscopic
means, such as e.g. scanning tunneling microscopy.Comment: 8 pages, 7 figures; minor correction
Staircase to Higher-Order Topological Phase Transitions
We find a series of topological phase transitions of increasing order, beyond
the more standard second-order phase transition in a one-dimensional
topological superconductor. The jumps in the order of the transitions depend on
the range of the pairing interaction, which is parametrized by an algebraic
decay with exponent . Remarkably, in the limit the order
of the topological transition becomes infinite. We compute the critical
exponents for the series of higher-order transitions in exact form and find
that they fulfill the hyperscaling relation. We also study the critical
behaviour at the boundary of the system and discuss potential experimental
platforms of magnetic atoms in superconductors.Comment: 5+5pages, 7 figures. Accepted as a Rapid Communicatio
Associations between religiosity and sexuality in a representative sample of Australian adults
Many studies have examined the influence on sexual attitudes and behavior of religious belief (i.e., religious denomination) or religiosity (e.g., attendance at services, subjective importance of religion). However, few studies have examined the combined effects of religion and religiosity on sexual attitudes and behavior. This study examined such effects in a representative sample of 19,307 Australians aged 16–59 years (response rate, 73.1%). The study compared members of four religious groups (Protestant, Catholic, Buddhist, Muslim) and two levels of frequency of attendance at religious service (less than monthly, at least monthly). Religious participants were compared to their non-religious peers in analyses adjusted for potential confounding by demographic variables. The outcomes were five sexual behaviors and five corresponding measures of sexual attitudes. The study revealed inconsistent patterns of association between religion/religiosity and a range of sexual behaviors and attitudes. In general, greater attendance at religious services was associated with more conservative patterns of behavior and attitudes. However, religious people who attended services infrequently were more similar to their non-religious peers than their more religious peers. The results of this study highlight the importance of considering not only religion or religiosity, but the intersection between these two variables
Fluctuation spectroscopy as a probe of granular superconducting diamond films
We present resistance versus temperature data for a series of boron-doped
nanocrystalline diamond films whose grain size is varied by changing the film
thickness. Upon extracting the fluctuation conductivity near to the critical
temperature we observe three distinct scaling regions -- 3D intragrain,
quasi-0D, and 3D intergrain -- in confirmation of the prediction of Lerner,
Varlamov and Vinokur. The location of the dimensional crossovers between these
scaling regions allows us to determine the tunnelling energy and the Thouless
energy for each film. This is a demonstration of the use of \emph{fluctuation
spectroscopy} to determine the properties of a superconducting granular system
Observation of a superconducting glass state in granular superconducting diamond
The magnetic field dependence of the superconductivity in nanocrystalline
boron doped diamond thin films is reported. Evidence of a glass state in the
phase diagram is presented, as demonstrated by electrical resistance and
magnetic relaxation measurements. The position of the phase boundary in the H-T
plane is determined from resistance data by detailed fitting to
zero-dimensional fluctuation conductivity theory. This allows determination of
the boundary between resistive and non-resistive behavior to be made with
greater precision than the standard ad hoc onset/midpoint/offset criterion
Dynamics of topological defects in a spiral: a scenario for the spin-glass phase of cuprates
We propose that the dissipative dynamics of topological defects in a spiral
state is responsible for the transport properties in the spin-glass phase of
cuprates. Using the collective-coordinate method, we show that topological
defects are coupled to a bath of magnetic excitations. By integrating out the
bath degrees of freedom, we find that the dynamical properties of the
topological defects are dissipative. The calculated damping matrix is related
to the in-plane resistivity, which exhibits an anisotropy and linear
temperature dependence in agreement with experimental data.Comment: 4 pages, as publishe
Finite-momentum Bose-Einstein condensates in shaken 2D square optical lattices
We consider ultracold bosons in a 2D square optical lattice described by the
Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is
applied to the system, which shakes the lattice along one of the diagonals. The
effect of the shaking is to renormalize the nearest-neighbor hopping
coefficients, which can be arbitrarily reduced, can vanish, or can even change
sign, depending on the shaking parameter. It is therefore necessary to account
for higher-order hopping terms, which are renormalized differently by the
shaking, and introduce anisotropy into the problem. We show that the
competition between these different hopping terms leads to finite-momentum
condensates, with a momentum that may be tuned via the strength of the shaking.
We calculate the boundaries between the Mott-insulator and the different
superfluid phases, and present the time-of-flight images expected to be
observed experimentally. Our results open up new possibilities for the
realization of bosonic analogs of the FFLO phase describing inhomogeneous
superconductivity.Comment: 7 pages, 7 figure
Structural lubricity: Role of dimension and symmetry
When two chemically passivated solids are brought into contact, interfacial
interactions between the solids compete with intrabulk elastic forces. The
relative importance of these interactions, which are length-scale dependent,
will be estimated using scaling arguments. If elastic interactions dominate on
all length scales, solids will move as essentially rigid objects. This would
imply superlow kinetic friction in UHV, provided wear was absent. The results
of the scaling study depend on the symmetry of the surfaces and the
dimensionalities of interface and solids. Some examples are discussed
explicitly such as contacts between disordered three-dimensional solids and
linear bearings realized from multiwall carbon nanotubes.Comment: 7 pages, 1 figur
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