High sensitivity thermodynamic measurements of fractional quantum Hall states in graphene

Thermodynamic quantities such as chemical potential and entropy provide information about many-body ground states that cannot be directly revealed by conventional transport measurements. In this talk, I will present a technique for high sensitivity measurement of the chemical potential in ultra-clean graphene heterostructures, based on a multilayer heterostructure with an embeded graphene layer that functions as an electrometer. An integrated on-chip heater further allows rapid modulation of the temperature, from which we extract the entropy per particle, △S/△N = -△μ/△T. We apply this technique to a high mobility monolayer graphene 2D electron gas at high magnetic fields, measuring the chemical potential and entropy of fractional quantum Hall states in N = 0 and N = 1 Landau levels (LLs) and electron solid states in the N = 2 and N=3 Landau levels. We compare our experimental sensitivity with that required to detect the ground state entropy associated with non-Abelian anyons, as are thought to appear at several filling factors in bilayer graphene.