High entropy materials are a relatively young new class of materials discovered in 2003. It possesses four kinds of special core effects as a result of its strong mixing nature such as (i) High entropy effect, (ii) Severe lattice distortion effect, (iii) Sluggish diffusion effect, and (iv) Cocktail effect. High Entropy Ceramics (HECs) are defined as the solid solutions of inorganic compounds (five or more cations sublattices) with one or more Wykoff sites shared by equal or nearly equal atomic ratios of multi-principal elements. HECs have gained the attention of researchers due to their fascinating properties. In this report, an A-site disordered high entropy perovskite (Bi0.2Na0.2Ba0.2Sr0.2Ca0.2)TiO3 ceramic was prepared via a solid-state reaction route. The XRD pattern and FESEM-EDS confirmed the formation of a single-phase solid solution with a tetragonal structure. A detailed study of the dielectric behavior of the sample was done. Modified Curie-Weiss law was fitted to the relative permittivity to analyze the relaxor behavior of the sample. HECs are highly tolerant to ions and their properties can be tailored by composition and according to the application purposes.
Ultra-short pulse propagation in nonlinear NRM has been investigated where a wide class of solutions for bright and dark solitons has been analyzed for distinct parameter ranges. Here the pulse propagation in nonlinear meta-material has been analytically by solving the nonlinear Schrödinger's equation (NLSE) in composite media expressing frequency dispersion in the dielectric permittivity (ε) and the magnetic permeability (µ). The solutions are exactly shown to be of trigonometric & localized types. The analytical and simulation based result has been utilized to study the intensity variation in case of a nonlinear meta-material which typically behaves as a negative refractive medium (NRM), for which both ε and µ exhibit frequency dispersion and are negative in nature. The peak of the pulse-intensity curve slowly decreases as the frequency increases towards the magnetic plasma frequency. The stability of the solitonic solutions has also been established.
We review recent advances in experimental and theoretical understanding of spin transport in strongly interacting Fermi gases. The central new phenomenon is the observation of a lower bound on the (bare) spin diffusivity in the strongly interacting regime. Transport bounds are of broad interest for the condensed matter community, with a conceptual similarity to observed bounds in shear viscosity and charge conductivity. We discuss the formalism of spin hydrodynamics, how dynamics are parameterized by transport coefficients, the effect of confinement, the role of scale invariance, the quasi-particle picture, and quantum critical transport. We conclude by highlighting open questions, such as precise theoretical bounds, relevance to other phases of matter, and extensions to lattice systems.
We report through 17O NMR, an unambiguous local determination of the intrinsic kagome lattice spin susceptibility as well as that created around non-magnetic defects issued from natural Zn/ Cu exchange in the S=1/2 (Cu2+) herbertsmithite ZnCu3(OH)6Cl2 compound. The issue of a singlet-triplet gap is addressed. The magnetic response around a defect is found to markedly differ from that observed in non-frustrated antiferromagnetic materials. Finally, we discuss our relaxation measurements in the light of Cu and Cl NMR data [cond-mat 070314] and suggest a flat q-dependence of the excitations.
We study the SU(4) Kondo effect in carbon nanotube quantum dots, where doubly degenerate orbitals form 4-electron ``shells''. The SU(4) Kondo behavior is investigated for one, two and three electrons in the topmost shell. While the Kondo state of two electrons is quenched by magnetic field, in case of an odd number of electrons two types of SU(2) Kondo effect may survive. Namely, the spin SU(2) state is realized in the magnetic field parallel to the nanotube (inducing primarily orbital splitting). Application of the perpendicular field (inducing Zeeman splitting) results in the orbital SU(2) Kondo effect.
We present simulation results suggesting that the stripe glass state described by Schmalian et al. for the Brazovskii model, cond-mat/0305420, may be dynamically unstable below the fluctuation-induced first-order transition temperature.
%auto-ignore This paper has been withdrawn by the authors because its results have been superceded by new experimental data and new theory presented in S.-K. Mo et al., cond-mat/0212110.
We show that the criticism of our paper [Phys. Rev. B 65, 125109 (2002)] by Wang, Millis, and Das Sarma [cond-mat/0206203] is based on a trivial mathematical mistake they have committed.
This paper has been withdrawn by the authors. It has been superceded by an improved investigation: ``Thermodynamic Generalized Compressibility in a Glass Forming Liquid,'' H. M. Carruzzo and C. C. Yu, cond-mat/0004320.
We comment on the recent paper "Magnetic Percolation and the Phase Diagram of the disordered RKKY model." D.J. Priour and S. Das Sarma, Phys Rev. Lett.{\bf 97}, 127201 (2006); cond-mat/0606532)
We reply to the recent comment cond-mat/9810097 on our original Letter `Roughening Transition of Interfaces in Disordered Systems', Phys. Rev. Lett. 81, 1469 (1998).
We refute the arguments by Anton in cond-mat/0004390, which set out to disprove the existence of a collapse transition for a randomly forced inelastic particle.
We point out the incorrect derivation of the gap equation in X.-J. Chen and H. Q. Lin [Phys. Rev. B 69 (2004) 104518; cond-mat/0306680] within the interlayer tunneling (ILT) model for multilayered cuprates. There, the local structure in k-space of the ILT effective interaction has not been taken into due account when the ILT model is generalized to the case of n layers per unit cell. This is a specific characteristic of the ILT model that, apart from giving rise to a highly nontrivial k-dependence of the gap function, is known to enhance the critical temperature Tc in a natural way. As a consequence, we argue that Chen and Lin's results cannot be employed, in their present form, for a quantitative interpretation of the high-pressure dependence of Tc in Bi-2212, as is done by X.-J. Chen et al. [cond-mat/0408587]. Moreover, when the generalization of X.-J. Chen et al. [cond-mat/0408587] is applied to the case n=2, it fails to reproduce the original ILT gap equation. However, a more careful analysis of the ILT model for multilayered cuprates, taking into account the nonuniform hole distribution among inequivalent layers, has been earlier suggested to describe the observed pressure dependence of Tc in homologous series of high-Tc cuprates.
We construct a new effective two-dimensional Hubbard model by taking the different electron occupancy on site into account. The mean field state of the new Hamiltonian gives rise to the gossamer superconducting state proposed by Laughlin recently(cond-mat/0209269).