7,335 research outputs found
Pairing state in multicomponent superconductors
We use the microscopic weak coupling theory to predict the pairing state in
superconductors of cubic, hexagonal, or tetragonal symmetry, where the order
parameter is multicomponent, i.e., transforms according to either a
2-dimensional or a 3-dimensional representation of the crystal point group. We
show that the superconducting phase usually breaks the time-reversal symmetry
for singlet multicomponent superconductors. The superconducting order parameter
for triplet superconductors in most cases turns out to be non-magnetic.Comment: 7 page
On the Construction and the Structure of Off-Shell Supermultiplet Quotients
Recent efforts to classify representations of supersymmetry with no central
charge have focused on supermultiplets that are aptly depicted by Adinkras,
wherein every supersymmetry generator transforms each component field into
precisely one other component field or its derivative. Herein, we study
gauge-quotients of direct sums of Adinkras by a supersymmetric image of another
Adinkra and thus solve a puzzle from Ref.[2]: The so-defined supermultiplets do
not produce Adinkras but more general types of supermultiplets, each depicted
as a connected network of Adinkras. Iterating this gauge-quotient construction
then yields an indefinite sequence of ever larger supermultiplets, reminiscent
of Weyl's construction that is known to produce all finite-dimensional unitary
representations in Lie algebras.Comment: 20 pages, revised to clarify the problem addressed and solve
D-module Representations of N=2,4,8 Superconformal Algebras and Their Superconformal Mechanics
The linear (homogeneous and inhomogeneous) (k, N, N-k) supermultiplets of the
N-extended one-dimensional Supersymmetry Algebra induce D-module
representations for the N=2,4,8 superconformal algebras.
For N=2, the D-module representations of the A(1,0) superalgebra are
obtained. For N=4 and scaling dimension \lambda=0, the D-module representations
of the A(1,1) superalgebra are obtained. For , the D-module
representations of the D(2,1;\alpha) superalgebras are obtained, with
determined in terms of the scaling dimension according to:
for k=4, i.e. the (4,4) supermultiplet,
for k=3, i.e. (3,4,1), and for k=1, i.e. (1,4,3). For
the (2,4,2) supermultiplet induces a D-module representation
for the centrally extended sl(2|2) superalgebra. For N=8, the (8,8) root
supermultiplet induces a D-module representation of the D(4,1) superalgebra at
the fixed value . A Lagrangian framework to construct
one-dimensional, off-shell, superconformal invariant actions from
single-particle and multi-particles D-module representations is discussed. It
is applied to explicitly construct invariant actions for the homogeneous and
inhomogeneous N=4 (1,4,3) D-module representations (in the last case for
several interacting supermultiplets of different chirality).Comment: 22 page
On Supergroups with Odd Clifford Parameters and Supersymmetry with Modified Leibniz Rule
We investigate supergroups with Grassmann parameters replaced by odd Clifford
parameters. The connection with non-anticommutative supersymmetry is discussed.
A Berezin-like calculus for odd Clifford variables is introduced. Fermionic
covariant derivatives for supergroups with odd Clifford variables are derived.
Applications to supersymmetric quantum mechanics are made. Deformations of the
original supersymmetric theories are encountered when the fermionic covariant
derivatives do not obey the graded Leibniz property. The simplest non-trivial
example is given by the N=2 SQM with a real multiplet and a cubic
potential. The action is real. Depending on the overall sign ("Euclidean" or
"Lorentzian") of the deformation, a Bender-Boettcher pseudo-hermitian
hamiltonian is encountered when solving the equation of motion of the auxiliary
field. A possible connection of our framework with the Drinfeld twist
deformation of supersymmetry is pointed out.Comment: Final version to be published in Int. J. Mod. Phys. A; 20 page
Twist Deformation of Rotationally Invariant Quantum Mechanics
Non-commutative Quantum Mechanics in 3D is investigated in the framework of
the abelian Drinfeld twist which deforms a given Hopf algebra while preserving
its Hopf algebra structure. Composite operators (of coordinates and momenta)
entering the Hamiltonian have to be reinterpreted as primitive elements of a
dynamical Lie algebra which could be either finite (for the harmonic
oscillator) or infinite (in the general case). The deformed brackets of the
deformed angular momenta close the so(3) algebra. On the other hand, undeformed
rotationally invariant operators can become, under deformation, anomalous (the
anomaly vanishes when the deformation parameter goes to zero). The deformed
operators, Taylor-expanded in the deformation parameter, can be selected to
minimize the anomaly. We present the deformations (and their anomalies) of
undeformed rotationally-invariant operators corresponding to the harmonic
oscillator (quadratic potential), the anharmonic oscillator (quartic potential)
and the Coulomb potential.Comment: 20 page
Comparative Analysis of the Electronic Energy Structure of Nanocrystalline Polymorphs of Y2O3 Thin Layers: Theory and Experiments
The results of fabrication and characterization of atomic structure of
nanocrystalline thin layers of Y2O3 in cubic and monoclinic phases is reported.
Experimental data demonstrate crystalline ordering in nanocrystalline films
with average grain size of ~10-14 nm both for cubic and monoclinic studied
structures. Density Functional Theory (DFT) based simulations demonstrate
insignificant differences of electronic structure of these phases in the bulk
and on the surfaces. Theoretical modeling also pointed out the significant
broadening of valence and conductive bands caused by means of energy levels
splitting in agreement with experimental data (X-ray photoelectron and
photoluminescence spectra). The presence of various intrinsic and extrinsic
defects (including surface adsorption of carbon mono- and dioxide) does not
promote visible changes in electronic structure of Y2O3 surface for both
studied phases. Optical absorption and luminescence measurements indicate
insignificant bandgap reduction of Y2O3 nanocrystalline layers and the very
little contribution from defect states. Simulation of extrinsic compression and
expanding demonstrate stability of the electronic structure of nanocrystalline
Y2O3 even under significant strain. Results of comprehensive studies
demonstrate that yttrium oxide based nanocrystalline layers are prospective for
various optical applications as a stable material.Comment: 24 pages, 13 figures, accepted to Applied Surface Scienc
Uncommon 2D Diamond-like Carbon Nanodots Derived from Nanotubes: Atomic Structure, Electronic States and Photonic Properties
In this article, we report the results of relatively facile fabrication of
carbon nanodots from single-walled and multi-walled carbon nanotubes (SWCNT and
MWCNT). The results of X-ray photoelectron spectroscopy (XPS) and Raman
measurements show that the obtained carbon nanodots are quasi-two-dimensional
objects with a diamond-like structure. Based on the characterization results, a
theoretical model of synthesized carbon nanodots was developed. The measured
absorption spectra demonstrate the similarity of the local atomic structure of
carbon nanodots synthesized from single-walled and multi-walled carbon
nanotubes. However, the photoluminescence (PL) spectra of nanodots synthesized
from both sources turned out to be completely different. Carbon dots fabricated
from MWCNTs exhibit PL spectra similar to nanoscale carbon systems with sp3
hybridization and a valuable edge contribution. At the same time nanodots
synthesized from SWCNTs exhibit PL spectra which are typical for quantum dots
with an estimated size of ~0.6-1.3 nm.Comment: 22 pages, 9 figures, to appear in PCC
The ways to improve the energy conversion efficiency in erbium-doped Gd 2 O 3 nanoparticles
The basic requirements for the crystal lattice and defectiveness of Gd 2 O 3 matrix as well as for the concentration of Er 3+ dopants to achieve the enhanced parameters of energy conversion in Gd 2 O 3 :Er nanoparticles are summarized. The obtained data allow to optimize and improve the functional characteristics of Gd 2 O 3 :Er-based down-conversion layers applying in solar cells. © 2018 Institute of Physics Publishing. All rights reserved.The work has been funded by the Ministry of Education and Science of the Russian Federation (Government task №3.1485.2017/4.6)
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