2017/11/16 by David F. Mross, Yuval Oreg, Ady Stern +2
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.121.026801
published as Phys. Rev. Lett. 121, 026801 (2018) · 8 pages, 8 figures
arxiv created 2017/11/16 · arxiv updated 2018/07/18
Electrons that are confined to a single Landau level in a two dimensional electron gas realize the effects of strong electron-electron repulsion in its purest form. The kinetic energy of individual electrons is completely quenched and all physical properties are dictated solely by many-body effects. A remarkable consequence is the emergence of new quasiparticles with fractional charge and exotic quantum statistics of which the most exciting ones are non-Abelian quasiparticles. A non-integer quantized thermal Hall conductance κxy (in units of temperature times the universal constant π2 kB2 /3 h; h is the Planck constant and kB the Boltzmann constant) necessitates the existence of such quasiparticles. It has been predicted, and verified numerically, that such states are realized in the clean half-filled first Landau level of electrons with Coulomb repulsion, with κxy being either 3/2 or 7/2. Excitingly, a recent experiment has indeed observed a half-integer value, which was measured, however, to be κxy=5/2. We resolve this contradiction within a picture where smooth disorder results in the formation of mesoscopic puddles with locally κxy=3/2 or 7/2. Interactions between these puddles generate a coherent macroscopic state, which is reflected in an extended plateau with quantized κxy=5/2. The topological properties of quasiparticles at large distances are determined by the macroscopic phase, and not by the microscopic puddle where they reside. In principle, the same mechanism might also allow non-Abelian quasiparticles to emerge from a system comprised of microscopic Abelian puddles.