Skyrmions in Higher Landau Levels

We calculate the energies of quasiparticles with large numbers of reversed spins (``skyrmions'') for odd integer filling factors 2k+1, k is greater than or equals 1. We find, in contrast with the known result for filling factor equals 1 (k = 0), that these quasiparticles always have higher energy than the fully polarized ones and hence are not the low energy charged excitations, even at small Zeeman energies. It follows that skyrmions are the relevant quasiparticles only at filling factors 1, 1/3 and 1/5.Comment: 10 pages, RevTe

Hund's Rule for Composite Fermions

We consider the ``fractional quantum Hall atom" in the vanishing Zeeman energy limit, and investigate the validity of Hund's maximum-spin rule for interacting electrons in various Landau levels. While it is not valid for {\em electrons} in the lowest Landau level, there are regions of filling factors where it predicts the ground state spin correctly {\em provided it is applied to composite fermions}. The composite fermion theory also reveals a ``self-similar" structure in the filling factor range $4/3>\nu>2/3$.Comment: 10 pages, revte

The Nature of the Hall Insulator

We have conducted an experimental study of the linear transport properties of the magnetic-field induced insulating phase which terminates the quantum Hall (QH) series in two dimensional electron systems. We found that a direct and simple relation exists between measurements of the longitudinal resistivity, $\rho_{xx}$, in this insulating phase and in the neighboring QH phase. In addition, we find that the Hall resistivity, $\rho_{xy}$, can be quantized in the insulating phase. Our results indicate that a close relation exists between the conduction mechanism in the insulator and in the QH liquid.Comment: RevTeX, 4 pages, 4 figure

A New Transport Regime in the Quantum Hall Effect

This paper describes an experimental identification and characterization of a new low temperature transport regime near the quantum Hall-to-insulator transition. In this regime, a wide range of transport data are compactly described by a simple phenomenological form which, on the one hand, is inconsistent with either quantum Hall or insulating behavior and, on the other hand, is also clearly at odds with a quantum-critical, or scaling, description. We are unable to determine whether this new regime represents a clearly defined state or is a consequence of finite temperature and sample-size measurements.Comment: Revtex, 3 pages, 2 figure

Higher spins dynamics in the closed string theory

The general $\sigma$-model-type string action including both massless and massive higher spins background fields is suggested. Field equations for background fields are followed from the requirement of quantum Weyl invariance. It is shown that renormalization of the theory can be produced level by level. The detailed consideration of background fields structure and corresponding fields equations is given for the first massive level of the closed bosonic string.Comment: 11 pages, report TSU/QFTD-36/9

Fractional Spin for Quantum Hall Effect Quasiparticles

We investigate the issue of whether quasiparticles in the fractional quantum Hall effect possess a fractional intrinsic spin. The presence of such a spin $S$ is suggested by the spin-statistics relation $S=\theta/2\pi$, with $\theta$ being the statistical angle, and, on a sphere, is required for consistent quantization of one or more quasiparticles. By performing Berry-phase calculations for quasiparticles on a sphere we find that there are two terms, of different origin, that couple to the curvature and can be interpreted as parts of the quasiparticle spin. One, due to self-interaction, has the same value for both the quasihole and quasielectron, and fulfills the spin-statistics relation. The other is a kinematical effect and has opposite signs for the quasihole and quasielectron. The total spin thus agrees with a generalized spin-statistics theorem $(S_{qh} + S_{qe})/2 = \theta/2\pi$. On the plane, we do not find any corresponding terms.Comment: 15 pages, RevTeX-3.

Quantum Hall Bilayers and the Chiral Sine-Gordon Equation

The edge state theory of a class of symmetric double-layer quantum Hall systems with interlayer electron tunneling reduces to the sum of a free field theory and a field theory of a chiral Bose field with a self-interaction of the sine-Gordon form. We argue that the perturbative renormalization group flow of this chiral sine-Gordon theory is distinct from the standard (non-chiral) sine-Gordon theory, contrary to a previous assertion by Renn, and that the theory is manifestly sensible only at a discrete set of values of the inverse period of the cosine interaction (beta). We obtain exact solutions for the spectra and correlation functions of the chiral sine-Gordon theory at the two values of beta at which the electron tunneling in bilayers is not irrelevant. Of these, the marginal case (beta^2=4) is of greatest interest: the spectrum of the interacting theory is that of two Majorana fermions with different, dynamically generated, velocities. For the experimentally observed bilayer 331 state at filling factor 1/2, this implies the trifurcation of electrons added to the edge. We also present a method for fermionizing the theory at the discrete points (integer beta^2) by the introduction of auxiliary degrees of freedom that could prove useful in other problems involving quantum Hall multilayers.Comment: revtex, epsf; 39 p., 4 figs; corrections to three equations; two-up postscript at http://www.sns.ias.edu/~leonid/csg-2up.p

Electromagnetic field angular momentum in condensed matter systems

Various electromagnetic systems can carry an angular momentum in their {\bf E} and {\bf B} fields. The electromagnetic field angular momentum (EMAM) of these systems can combine with the spin angular momentum to give composite fermions or composite bosons. In this paper we examine the possiblity that an EMAM could provide an explanation of the fractional quantum Hall effect (FQHE) which is complimentary to the Chern-Simons explanation. We also examine a toy model of a non-BCS superconductor (e.g. high $T_c$ superconductors) in terms of an EMAM. The models presented give a common, simple picture of these two systems in terms of an EMAM. The presence of an EMAM in these systems might be tested through the observation of the decay modes of a charged, spin zero unstable particle inside one of these systems.Comment: 17 pages, no figures, to be published in Phys. Rev.

Interlayer Exchange Interactions, SU(4) Soft Waves and Skyrmions in Bilayer Quantum Hall Ferromagnets

The Coulomb exchange interaction is the driving force for quantum coherence in quantum Hall systems. We construct a microscopic Landau-site Hamiltonian for the exchange interaction in bilayer quantum Hall ferromagnets, which is characterized by the SU(4) isospin structure. By taking a continuous limit, the Hamiltonian gives rise to the SU(4) nonlinear sigma model in the von-Neumann-lattice formulation. The ground-state energy is evaluated at filling factors $\nu =1,2,3,4$. It is shown at $\nu =1$ that there are 3 independent soft waves, where only one soft wave is responsible for the coherent tunneling of electrons between the two layers. It is also shown at $\nu =1$ that there are 3 independent skyrmion states apart from the translational degree of freedom. They are CP$^{3}$ skyrmions enjoying the spin-charge entanglement confined within the \LLL.Comment: 12 pages, 2 figure

Anisotropic Transport of Quantum Hall Meron-Pair Excitations

Double-layer quantum Hall systems at total filling factor $\nu_T=1$ can exhibit a commensurate-incommensurate phase transition driven by a magnetic field $B_{\parallel}$ oriented parallel to the layers. Within the commensurate phase, the lowest charge excitations are believed to be linearly-confined Meron pairs, which are energetically favored to align with $B_{\parallel}$. In order to investigate this interesting object, we propose a gated double-layer Hall bar experiment in which $B_{\parallel}$ can be rotated with respect to the direction of a constriction. We demonstrate the strong angle-dependent transport due to the anisotropic nature of linearly-confined Meron pairs and discuss how it would be manifested in experiment.Comment: 4 pages, RevTex, 3 postscript figure