In the present paper the Analytical approximate solution of a fractional diffusion equation is deduced with the help of powerful Variational Iteration method. By using an initial value, the explicit ...solutions of the equation for different cases have been derived, which accelerate the rapid convergence of the series solution. The present method performs extremely well in terms of efficiency and simplicity. Numerical results for different particular cases of the problem are presented graphically.
We show, theoretically, that a heterostructure of monolayer FeTe1−xSex-a superconducting quantum spin Hall material-with a monolayer of FeTe-a bicollinear antiferromagnet-realizes a higher order ...topological superconductor phase characterized by emergent Majorana zero modes pinned to the sample corners. We provide a minimal effective model for this system, analyze the origin of higher order topology, and fully characterize the topological phase diagram. Despite the conventional s-wave pairing, we find a rather surprising emergence of a novel topological nodal superconductor in the phase diagram. Featured by edge-dependent Majorana flat bands, the topological nodal phase is protected by an antiferromagnetic chiral symmetry. We also discuss the experimental feasibility, the estimation of realistic model parameters, and the robustness of the Majorana corner modes against magnetic and potential disorder. Our work provides a new experimentally feasible high-temperature platform for both higher order topology and non-Abelian Majorana physics.
Motivated by recent experiments on FeTe_{1-x}Se_{x}, we construct an explicit minimal model of an iron-based superconductor with band inversion at the Z point and nontopological bulk s_{±} pairing. ...While there has been considerable interest in Majorana zero modes localized at vortices in such systems, we find that our model-without any vortices-intrinsically supports 1D helical Majorana modes localized at the hinges between (001) and (100) or (010) surfaces, suggesting that this is a viable platform for observing "higher-order" topological superconductivity. We provide a general theory for these hinge modes and discuss their stability and experimental manifestation. Our work indicates the possible experimental observability of hinge Majorana modes in iron-based topological superconductors.
In a coalescence plus fragmentation approach we calculate the heavy baryon/meson ratio and the
p
T
spectra of charmed hadrons
D
0
,
D
s
and
Λ
c
+
in a wide range of transverse momentum from low
p
T
...up to about 10 GeV and discuss their ratios from RHIC to LHC energies without any change of the coalescence parameters. We have included the contribution from decays of heavy hadron resonances and also the one due to fragmentation of heavy quarks which do not undergo the coalescence process. The coalescence process is tuned to have all charm quarks hadronizing in the
p
T
→
0
limit and at finite
p
T
charm quarks not undergoing coalescence are hadronized by independent fragmentation. The
p
T
dependence of the baryon/meson ratios are found to be sensitive to the masses of coalescing quarks, in particular the
Λ
c
/
D
0
can reach values of about
1
÷
1.5
at
p
T
≈
3
GeV, or larger, similarly to the light baryon/meson ratio like
p
/
π
and
Λ
/
K
, however a marked difference is a quite weak
p
T
dependence with respect to the light case, such that a larger value at intermediate
p
T
implies a relatively large value also for the integrated yields. A comparison with other coalescence model and with the prediction of thermal model is discussed.
In this review fundamentals of optical parametric oscillator and different phase matching situation have been discussed. Requirement of nonlinear crystal and properties of some mid-IR and IR ...transmitting crystal have been discussed. Present status of generation of tunable radiation in mid-IR to IR spectral range by OPO based on ZnGeP
2
crystal and other techniques and its applications has been discussed.
In this paper, we report the effect of different plasticizers, such as poly ethylene glycol, propylene carbonate, ethylene carbonate and dimethyl carbonate on the ionic conductivity and dielectric ...relaxation of PEO-LiClO4 solid polymer electrolytes. The highest ionic conductivity is obtained for polymer electrolyte plasticized with poly ethylene glycol. The temperature dependence of ionic conductivity follows the well known Vogel–Tamman–Fulcher relation which indicates a strong coupling of ionic and segmental motions for all compositions. The experimental data for the complex dielectric permittivity and electric modulus have been studied using Havriliak–Negami function for the understanding of ion dynamics. Maximum dielectric strength is obtained for polymer electrolyte plasticized with poly ethylene glycol. The modulus data have been analyzed using non-exponential Kohlrausch–Williams–Watts (KWW) function. It is observed that the non-exponential parameter β is quite lower than unity, suggesting highly a non-exponential relaxation exists in these materials. The temperature dependence of relaxation times obtained from dielectric and modulus formalisms also follow Vogel–Tamman–Fulcher relation for all plasticizers in the compositions.
We investigate localization properties in a family of deterministic (i.e., no disorder) nearest neighbor tight binding models with quasiperiodic on site modulation. We prove that this family is ...self-dual under a generalized duality transformation. The self-dual condition for this general model turns out to be a simple closed form function of the model parameters and energy. We introduce the typical density of states as an order parameter for localization in quasiperiodic systems. By direct calculations of the inverse participation ratio and the typical density of states we numerically verify that this self-dual line indeed defines a mobility edge in energy separating localized and extended states. Our model is a first example of a nearest neighbor tight binding model manifesting a mobility edge protected by a duality symmetry. We propose a realistic experimental scheme to realize our results in atomic optical lattices and photonic waveguides.
We establish quasi-two-dimensional thin films of iron-based superconductors (FeSCs) as a new high-temperature platform for hosting intrinsic time-reversal-invariant helical topological ...superconductivity (TSC). Based on the combination of Dirac surface state and bulk extended s-wave pairing, our theory should be directly applicable to a large class of experimentally established FeSCs, opening a new TSC paradigm. In particular, an applied electric field serves as a "topological switch" for helical Majorana edge modes in FeSC thin films, allowing for an experimentally feasible design of gate-controlled helical Majorana circuits. Applying an in-plane magnetic field drives the helical TSC phase into a higher-order TSC carrying corner-localized Majorana zero modes. Our proposal should enable the experimental realization of helical Majorana fermions.
self-consistent theory for graphene transport Adam, Shaffique; Hwang, E.H; Galitski, V.M ...
Proceedings of the National Academy of Sciences - PNAS,
11/2007, Volume:
104, Issue:
47
Journal Article
Peer reviewed
Open access
We demonstrate theoretically that most of the observed transport properties of graphene sheets at zero magnetic field can be explained by scattering from charged impurities. We find that, contrary to ...common perception, these properties are not universal but depend on the concentration of charged impurities nimp. For dirty samples (250 x 10¹⁰ cm⁻² < nimp < 400 x 10¹⁰ cm⁻²), the value of the minimum conductivity at low carrier density is indeed 4e²/h in agreement with early experiments, with weak dependence on impurity concentration. For cleaner samples, we predict that the minimum conductivity depends strongly on nimp, increasing to 8e²/h for nimp almost equal to 20 x 10¹⁰ cm⁻². A clear strategy to improve graphene mobility is to eliminate charged impurities or use a substrate with a larger dielectric constant.
Semiconducting nanowires in proximity to superconductors are promising experimental systems for realizing the elusive Majorana fermions, which, because of their non-abelian anyonic braiding ...statistics, may ultimately be used as building blocks for topological quantum computers. A serious challenge in the experimental realization of the Majorana fermions is the suppression of topological superconductivity by disorder together with the tunability of carrier density for semiconductors in close proximity to superconductors. Here we show that Majorana fermions that are protected by a disorder robust topological gap can occur at the ends of a chain of gate-tunable quantum dots connected by s-wave superconductors. Such an array of quantum dots provides the simplest realization of Majorana fermions in systems as simple as a few quantum dot array. The proposed system provides a very practical and easily realizable experimental platform for the observation of non-abelian Majorana modes.
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