Condensed Matter Theory

Abstract:

There is growing experimental and theoretical evidence that very clean two-dimensional electron systems form unidirectional charge density waves (UCDW) or "striped" states at low temperatures and at Landau level filling fractions of the form v = M + x with 4 < M < 10 an integer and 0.4 ≳ x ≳ 0.6. Following previous work, we model the striped state using a Hartree-Fock approach. We construct the low-energy excitations of the system by making smooth deformations of the stripe edges analogous to the construction of edge state excitations of quantum Hall droplets. These low-energy excitations are described as a coupled Luttinger liquid theory, as discussed previously by MacDonald and Fisher [Phys. Rev. B 61, 5724 (2000)]. Here, we extend that work and explicitly derive all of the parameters of this low energy theory using a Hartree-Fock approach. We also make contact with the equivalent low-energy hydrodynamic approach of Fogler and Vinokur [Phys. Rev. Lett. 84, 5828 (2000)] and similarly derive the parameters of this theory. As examples of the use of these results, we explicitly calculate the low-energy excitation spectrum and study tunneling into the striped state.

Abstract:

The dynamics of the deformations of a moving contact line was analyzed using two different dissipation mechanism. The contact lines relax to their equilibrium from a distorted configuration with a characteristic inverse decay time because of their anomalous elasticity. It is found that the velocity of the contact lines depends on the dissipation mechanism of the system.

Abstract:

The dynamics of the deformations of a moving contact line is studied assuming two different dissipation mechanisms. It is shown that the characteristic relaxation time for a deformation of wavelength 2pi/|k| of a contact line moving with velocity v is given as tau(-1)(k)=c(v)|k|. The velocity dependence of c(v) is shown to depend drastically on the dissipation mechanism: we find c(v)=c(v=0)-2v for the case in which the dynamics is governed by microscopic jumps of single molecules at the tip (Blake mechanism), and c(v) approximately c(v=0)-4v when viscous hydrodynamic losses inside the moving liquid wedge dominate (de Gennes mechanism). We thus suggest that the debated dominant dissipation mechanism can be experimentally determined using relaxation measurements similar to the Ondarcuhu-Veyssie experiment [T. Ondarcuhu and M. Veyssie, Nature 352, 418 (1991)].