Condensed Matter Theory

Abstract:

We construct a wave function, generalizing the well-known Moore-Read Pfaffian, that describes spinless electrons at filling fraction ν=2/5 (or bosons at filling fraction ν=2/3) as the ground state of a very simple three body potential. We find, analogous to the Pfaffian, that when quasiholes are added there is a ground state degeneracy which can be identified as zero modes of the quasiholes. The zero modes are identified as having semionic statistics. We write this wave function as a correlator of the Virasoro minimal model conformal field theory M (5,3). Since this model is nonunitary, we conclude that this wave function is likely a quantum critical state. Nonetheless, we find that the overlaps of this wave function with exact diagonalizations in the lowest and first excited Landau level are very high, suggesting that this wave function may have experimental relevance for some transition that may occur in that regime. © 2007 The American Physical Society.

Abstract:

Certain well known quantum Hall states-including the Laughlin states, the Moore-Read Pfaffian, and the Read-Rezayi Parafermion states-can be defined as the unique lowest degree symmetric analytic function that vanishes as at least p powers as some number (g+1) of particles approach the same point. Analogously, these same quantum Hall states can be generated as the exact highest density zero energy state of simple angular momentum projection operators. Following this theme we determine the highest density zero energy state for many other values of p and g. © 2007 The American Physical Society.

Abstract:

We explore numerically the feasibility of using chemical patterning to control the size and polydispersity of micrometer-scale drops. The simulations suggest that it is possible to sort drops by size or wetting properties by using an array of hydrophilic stripes of different widths. We also demonstrate that monodisperse drops can be generated by exploiting the pinning of a drop on a hydrophilic stripe. Our results follow from using a lattice Boltzmann algorithm to solve the hydrodynamic equations of motion of the drops and demonstrate the applicability of this approach as a design tool for micofluidic devices with chemically patterned surfaces.