39,904 research outputs found
Novel superconductivity: from bulk to nano systems
We begin with an introduction of superconductivity by giving a brief history of the phenomenon. The phenomenological Ginzburg–Landau theory and the microscopic theory of Bardeen, Cooper and Schrieffer are outlined. In view of recently available multi-band superconductors, relevant theories of both types are discussed. Unlike the traditional GL theory an extended GL theory is developed relevant to temperatures below the critical temperature. Superconductivity in a nanosystem is the highlight of the remaining part of the paper. Theories and experiments are discussed to give an interested reader an updated account and overview of what is new in this active area of research
Caloric curve in Au + Au collisions
Realistic caloric curves are obtained for reaction with
incident energy ranging from 35 to 130 MeV/nucleon in the dynamic statistical
multifragmentation model. It is shown that for excitation energy 3 to 8
MeV/nucleon, the temperature remains constant in the range 5 to 6 MeV, which is
close to experiment. The mechanism of energy deposition through the
tripartition of colliding system envisaged in this model together with
inter-fragment nuclear interaction are found to play important role. A possible
signature of liquid-gas phase transition is seen in the specific heat
distribution calculated from these caloric curves, and the critical temperature
is found to be 6 to 6.5 MeV.Comment: Revtex, 10 pages, 4 postscipt figures, To appear in Phys. Rev. C
(Rapid Communications
Strain induced band gap deformation of H/F passivated graphene and h-BN sheet
Strain induced band gap deformations of hydrogenated/fluorinated graphene and
hexagonal BN sheet have been investigated using first principles density
functional calculations. Within harmonic approximation, the deformation is
found to be higher for hydrogenated systems than for the fluorinated systems.
Interestingly, our calculated band gap deformation for hydrogenated/fluorinated
graphene and BN sheets are positive, while those for pristine graphene and BN
sheet are found to be negative. This is due to the strong overlap between
nearest neighbor {\pi} orbitals in the pristine sheets, that is absent in the
passivated systems. We also estimate the intrinsic strength of these materials
under harmonic uniaxial strain, and find that the in-plane stiffness of
fluorinated and hydrogenated graphene are close, but larger in magnitude as
compared to those of fluorinated and hydrogenated BN sheet.Comment: Submitted to PR
Incorporating Radial Flow in the Lattice Gas Model for Nuclear Disassembly
We consider extensions of the lattice gas model to incorporate radial flow.
Experimental data are used to set the magnitude of radial flow. This flow is
then included in the Lattice Gas Model in a microcanonical formalism. For
magnitudes of flow seen in experiments, the main effect of the flow on
observables is a shift along the axis.Comment: Version accepted for publication in Phys. Rev. C, Rapid Communicatio
Strong correlation effects and optical conductivity in electron doped cuprates
We demonstrate that most features ascribed to strong correlation effects in
various spectroscopies of the cuprates are captured by a calculation of the
self-energy incorporating effects of spin and charge fluctuations. The self
energy is calculated over the full doping range of electron-doped cuprates from
half filling to the overdoped system. The spectral function reveals four
subbands, two widely split incoherent bands representing the remnant of the
split Hubbard bands, and two additional coherent, spin- and charge-dressed
in-gap bands split by a spin-density wave, which collapses in the overdoped
regime. The incoherent features persist to high doping, producing a remnant
Mott gap in the optical spectra, while transitions between the in-gap states
lead to pseudogap features in the mid-infrared.Comment: 5 pages, 4 figure
Driven Heisenberg Magnets: Nonequilibrium Criticality, Spatiotemporal Chaos and Control
We drive a -dimensional Heisenberg magnet using an anisotropic current.
The continuum Langevin equation is analysed using a dynamical renormalization
group and numerical simulations. We discover a rich steady-state phase diagram,
including a critical point in a new nonequilibrium universality class, and a
spatiotemporally chaotic phase. The latter may be `controlled' in a robust
manner to target spatially periodic steady states with helical order.Comment: 7 pages, 2 figures. Published in Euro. Phys. Let
Localization in one-dimensional incommensurate lattices beyond the Aubry-Andr\'e model
Localization properties of particles in one-dimensional incommensurate
lattices without interaction are investigated with models beyond the
tight-binding Aubry-Andr\'e (AA) model. Based on a tight-binding t_1 - t_2
model with finite next-nearest-neighbor hopping t_2, we find the localization
properties qualitatively different from those of the AA model, signaled by the
appearance of mobility edges. We then further go beyond the tight-binding
assumption and directly study the system based on the more fundamental
single-particle Schr\"odinger equation. With this approach, we also observe the
presence of mobility edges and localization properties dependent on
incommensuration.Comment: 5 pages, 6 figure
Track clustering with a quantum annealer for primary vertex reconstruction at hadron colliders
Clustering of charged particle tracks along the beam axis is the first step
in reconstructing the positions of hadronic interactions, also known as primary
vertices, at hadron collider experiments. We use a 2036 qubit D-Wave quantum
annealer to perform track clustering in a limited capacity on artificial events
where the positions of primary vertices and tracks resemble those measured by
the Compact Muon Solenoid experiment at the Large Hadron Collider. The
algorithm, which is not a classical-quantum hybrid but relies entirely on
quantum annealing, is tested on a variety of event topologies from 2 primary
vertices and 10 tracks up to 5 primary vertices and 15 tracks. It is
benchmarked against simulated annealing executed on a commercial CPU
constrained to the same processor time per anneal as time in the physical
annealer, and performance is found to be comparable for small numbers of
vertices with an intriguing advantage noted for 2 vertices and 16 tracks
Localization in one dimensional lattices with non-nearest-neighbor hopping: Generalized Anderson and Aubry-Andr\'e models
We study the quantum localization phenomena of noninteracting particles in
one-dimensional lattices based on tight-binding models with various forms of
hopping terms beyond the nearest neighbor, which are generalizations of the
famous Aubry-Andr\'e and noninteracting Anderson model. For the case with
deterministic disordered potential induced by a secondary incommensurate
lattice (i.e. the Aubry-Andr\'e model), we identify a class of self dual
models, for which the boundary between localized and extended eigenstates are
determined analytically by employing a generalized Aubry-Andr\'e
transformation. We also numerically investigate the localization properties of
non-dual models with next-nearest-neighbor hopping, Gaussian, and power-law
decay hopping terms. We find that even for these non-dual models, the
numerically obtained mobility edges can be well approximated by the
analytically obtained condition for localization transition in the self dual
models, as long as the decay of the hopping rate with respect to distance is
sufficiently fast. For the disordered potential with genuinely random
character, we examine scenarios with next-nearest-neighbor hopping,
exponential, Gaussian, and power-law decay hopping terms numerically. We find
that the higher order hopping terms can remove the symmetry in the localization
length about the energy band center compared to the Anderson model.
Furthermore, our results demonstrate that for the power-law decay case, there
exists a critical exponent below which mobility edges can be found. Our
theoretical results could, in principle, be directly tested in shallow atomic
optical lattice systems enabling non-nearest-neighbor hopping.Comment: 18 pages, 24 figures updated with additional reference
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