Thursday's seminar

[Cond.Matt. & Stat.Mech.Section]

Seminar  on     Disorder and strong electron correlations

 

Thursday, 10 February   -  11:30 a.m.

 

Luigi Stasi Seminar Room,  Leonardo Building - first floor 

 

Gunnar MOELLER     ( Cavendish Laboratory, Cambridge )



"Quasiparticles and   the topological order of the \nu=5/2 state"

Abstract

 

We present evidence supporting the weakly paired Moore-Read phase in the half-filled second Landau level, focusing on some of the *qualitative* features of its excitations.  Based on numerical studies, we study both skyrmions and neutral excitations.  Skyrmions are found to be present at low enough fields, and are promoted by disorder [1]. We show that systems with odd particle number at the flux N_\phi=2N-3 can be interpreted as a neutral fermion mode of one unpaired fermion, which is gapped. The energetics of neutral fermions interacting with pairs of quasiparticles is found to be in agreement with predictions for non-abelian statistics of the Ising type with degenerate fusion channels 1 and \psi [2].  In particular, we discuss signatures of the \nu=5/2 Hall liquid in photoluminescence (PL) experiments [3]:  The neutral fermion mode is found to have two distinct minima, resulting in a double-peak structure in the PL spectrum [2].  On the other hand, a valence hole in proximity to the 2DEG induces a disorder potential that locally favours skyrmions.  Thus PL signals as a probe for spin polarization in the groundstate should be interpreted conservatively.

 

[1] A. Wójs, G. Möller, S. H. Simon, and N. R. Cooper, Phys. Rev. Lett. 104, 086801 (2010).

[2] G. Möller, A. Wójs, N. R. Cooper, arXiv:1009.4956.

[3] Stern et al., Phys. Rev. Lett. 105, 096801 (2010).