Abstract: The quantum Hall state at filling fraction ν=5/2 has attracted much attention in the past few decades, partly because it is a promising host of non-Abelian topological orders. Numerical studies modeling the quantum hall effect at filling fraction 5/2 predict either the Pfaffian or its particle hole conjugate, the anti-Pfaffian state. However, recent experiments, very surprisingly, appear to favor a quantized thermal hall conductivity with quantum number K = 5/2 , rather than the value K = 7/2 or K = 3/2 expected for the Pfaffian or anti-Pfaffian state, respectively.

In this talk I will discuss a mechanism for disorder to induce a set of new phases in the ν=5/2 quantum Hall system. These include a “thermal metal” phase with quantized electric Hall response, and a new topological order called PH-Pfaffian, which has a quantized thermal Hall conductivity K=5/2, in agreement with the recent measurement.