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A. V. Balatsky

Publications and source records attributed to A. V. Balatsky.

176 records · Page 10Linked to original sources
arXiv1995

Properties of Odd Gap Superconductors

We discuss the class of superconductors which have pairing correlations which are odd in frequency, as introduced originally by Berezinskii and more recently by Balatsky and Abrahams. As follows from the equations of motion, a natural definition of the thermodynamic order parameter of the odd-pairing state is the expectation value of a composite operator which couples a Cooper pair to a spin or charge fluctuation. We use a model pairing hamiltonian to describe properties of the odd-pairing composite-operator condensate. We show that the superfluid stiffness is positive, we discuss superconductive tunneling with an ordinary superconductor and we derive other thermodynamic and transport properties.

cond-mat↗
arXiv1994

Odd time magnetic correlations and chiral spin nematics

The magnetic analog of odd-time superconducting order is introduced. It is shown that the classification of possible odd-time magnetic states admits the existence of a novel state - the chiral spin nematic - which is characterized by an odd-in-time spin-spin correlation function.The known example of the chiral spin liquid appears naturally in this approach. The equal-time correlation function of these odd-in-time states involves non-trivial three spin correlations.

cond-mat↗
arXiv1994

Impurity-Induced Virtual Bound States in d-Wave Superconductors

It is shown that a single, strongly scattering impurity produces a bound or a virtual bound quasiparticle state inside the gap in a $d$-wave superconductor. The explicit form of the bound state wave function is found to decay exponentially with angle-dependent range. These states provide a natural explanation of the second Cu NMR rate arising from the sites close to Zn impurities in the cuprates. Finally, for finite concentration of impurities in a $d$-wave superconductor, we reexamine the growth of these states into an impurity band, and discuss the Mott criterion for this band.

cond-mat↗
arXiv1994

Superconducting Fluctuations in a Multi-Band 1D Hubbard Model

A renormalization-group and bosonization approach for a multi-band Hubbard Hamiltonian in one dimension is described. Based on the limit of many bands, it is argued that this Hamiltonian with bare repulsive electron-electron interactions is scaled under specific conditions to a model in which superconducting fluctuations dominate.

cond-mat↗
arXiv1994

The Influence of Magnetic Imperfections on the Low Temperature Properties of D-wave Superconductors

We consider the influence of planar ``magnetic" imperfections which destroy the local magnetic order, such as Zn impurities or $Cu^{2+}$ vacancies, on the low temperature properties of the cuprate superconductors. In the unitary limit, at low temperatures, for a $d_{x^2-y^2}$ pairing state such imperfections produce low energy quasiparticles with an anistropic spectrum in the vicinity of the nodes. We find that for the $La_{2-x}Sr_xCuO_4$ system, one is in the {\em quasi-one-dimensional} regime of quasiparticle scattering, discussed recently by Altshuler, Balatsky, and Rosengren, for impurity concentrations in excess of $\sim 0.16\%$ whereas YBCO$_7$ appears likely to be in the true 2D scattering regime for Zn concentrations less than $1.6\%$. We show the neutron scattering results of Mason et al. \cite{Aeppli} on $La_{1.86}Sr_{0.14}CuO_4$ provide strong evidence for ``dirty d-wave" superconductivity in their samples. We obtain simple expressions for the dynamic spin susceptibility and $^{63}Cu$ spin-lattice relaxation time, $^{63}T_1$, in the superconducting state.

cond-mat↗
arXiv1994

Impurities and Conductivity in a D-wave Superconductor

Impurity scattering in the unitary limit produces low energy quasiparticles with anisotropic spectrum in a two-dimensional $d$-wave superconductor. We describe a new {\em quasi-one-dimensional } limit of the quasiparticle scattering, which might occur in a superconductor with short coherence length and with {\em finite} impurity potential range. The dc conductivity in a $d$-wave superconductor is predicted to be proportional to the normal state scattering rate and is impurity-{\em dependent}. We show that {\em quasi-one-dimensional } regime might occur in high-$T_c$ superconductors with Zn impurities at low temp\ eratures $T\lesssim 10$~K

cond-mat↗
arXiv1994

Composite operators for BCS Superconductor

The new form of the composite operator generalizing the Cooper pairs for a BCS superconductor is introduced. The approach is similar to the derivation of the composite operator of the odd - frequency superconductors. The examples of the $d_{x^2-y^2}-,~d_{xy}-$ and $p-$ wave composite operators for a 2D $t-J$ model are given.

cond-mat↗
arXiv1993

Impurities and Quasi-One Dimensional Transport in a D-wave Superconductor

Impurity scattering in the unitary limit produces low energy quasiparticles with anisotropic spectrum in a two-dimensional $d$-wave superconductor. We describe a new {\em quasi-one-dimensional } limit of the quasiparticle scattering, which might occur in a superconductor with short coherence length and with {\em finite} impurity potential range. The dc conductivity in a $d$-wave superconductor is predicted to be proportional to the normal state scattering rate and is impurity-{\em dependent}. We show that the {\em quasi-one-dimensional } regime occurs in high-$T_c$ superconductors at low temperatures $T\lesssim 10$~K. We argue that the impurities produce weak localization, in the {\em orthogonal } universality class, of the quasiparticles in a $d$-wave superconductor.

cond-mat↗
arXiv1993

Properties of Odd Gap Superconductors

A new class of superconductors with the gap function {\it odd} under time reversal is considered. Some of the physical properties of these superconductors such as the Meissner effect, composite condensate, gapless spectrum and transition from the {\it odd} gap superconductor to the BCS state at lower temperatures are discussed.

cond-mat↗
arXiv1993

On superconducting instability in non-Fermi liquid: scaling approach

The superconducting instability in a non-Fermi liquid in $ d>1$ is considered. For a particular form of the single particle spectral function with homogeneous scaling $A(Λk, Λω) = Λ^α A(k, ω)$ it is shown that the pair susceptibility is also a scaling function of temperature with power defined by $α$. We find three different regimes depending on the scaling constant. The BCS result is recovered for $α= -1$ and it corresponds to a marginal scaling of the coupling constant. For $α> -1$ the superconducting transition happens above some critical coupling. In the opposite case of $α< -1$ for any fixed coupling the system undergoes a transition at low temperatures. Possible implications for theories of high-$T_c$ with a superconducting transition driven by the interlayer Josephson tunneling are discussed. 1 ps file for fig is attached at the bottom of the tex file.

cond-mat↗
arXiv1993

Even and odd-frequency pairing correlations in 1-D t-J-h model: a comparative study

An equal time version of odd-frequency pairing for a generalized $t-J$ model is introduced. It is shown that the composite operators describing binding of Cooper pairs with magnetization fluctuations naturally appear in this approach. The pairing correlations in both BCS and odd-frequency channels are investigated exactly in 1D systems with up to 16 sites. Our results indicate that at some range of parameters odd-frequency correlations become comparable, however smaller than BCS pairing correlations. It is speculated that the spin and density fluctuations in the frustrated model lead to the enhancement of the odd gap susceptibilities. 4 postscript figure files are attached at the bottom of the tex file.

cond-mat↗
arXiv1992

Quaternion Generalization of the Laughlin State and the Three Dimensional Fractional QHE

The 3D state of strongly correlated electrons is proposed, which in the external magnetic field $\vec B$ exhibits the fractional quantum Hall effect, with the zero temperature conductivity tensor $σ_{ij} = (e^2/h)(1/m) \sum_k ε_{ijk} B^k/\mid \vec B\mid $. The analog of Landau and Laughlin states in 3D are given using quaternion coordinates as generalization of complex coordinates. We discuss the notion of the fractional statistics in 3D introduced recently by Haldane.

cond-mat↗