Showing papers by "Eugene Demler published in 1999"

Spin Bose-glass phase in bilayer quantum Hall systems at nu=2

Abstract: We develop an effective spin theory to describe magnetic properties of the $ u=2$ Quantum Hall bilayer systems. In the absence of disorder this theory gives quantitative agreement with the results of microscopic Hartree-Fock calculations, and for finite disorder it predicts the existence of a novel spin Bose glass phase. The Bose glass is characterized by the presence of domains of canted antiferromagnetic phase with zero average antiferromagnetic order and short range mean antiferromagnetic correlations. It has infinite antiferromagnetic transverse susceptibility, finite longitudinal spin susceptibility and specific heat linear in temperature. Transition from the canted antiferromagnet phase to the spin Bose glass phase is characterized by a universal value of the longitudinal spin conductance.

Electromodulation of the Bilayered ν = 2 Quantum Hall Phase Diagram

Abstract: We make a number of precise experimental predictions for observing the various magnetic phases, and the quantum phase transitions between them, in the $\ensuremath{ u}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ bilayered quantum Hall system. In particular, we analyze the effect of an external bias voltage on the quantum phase diagram, finding that a finite bias should readily enable the experimental observation of the recently predicted novel canted antiferromagnetic phase in transport and spin polarization measurements.

Topological doping and the stability of stripe phases

Abstract: We analyze the properties of a general Ginzburg-Landau free energy with competing order parameters, long-range interactions, and global constraints (eg, a fixed value of a total {open_quotes}charge{close_quotes}) to address the physics of stripe phases in underdoped high-T{sub c} and related materials For a local free energy limited to quadratic terms of the gradient expansion, only uniform or phase-separated configurations are thermodynamically stable {open_quotes}Stripe{close_quotes} or other nonuniform phases can be stabilized by long-range forces, but can only have nontopological (in-phase) domain walls where the components of the antiferromagnetic order parameter never change sign, and the periods of charge and spin-density waves coincide The {ital antiphase} domain walls observed experimentally require physics on an intermediate length scale, and they are absent from a model that involves only long-distance physics Dense stripe phases can be stable even in the absence of long-range forces, but domain walls always attract at large distances; ie, there is a ubiquitous tendency to phase separation at small doping The implications for the phase diagram of underdoped cuprates are discussed {copyright} {ital 1999} {ital The American Physical Society}