Detection of fractional quantum Hall states by entropy-sensitive measurements

The thermopower of a clean two-dimensional electron system is directly proportional to the entropy per charge carrier and can probe strongly interacting quantum phases such as fractional quantum Hall liquids. In particular, thermopower is a valuable parameter to probe the quasiparticle statistics that give rise to excess entropy in certain even-denominator fractional quantum Hall states. Here we demonstrate that the magneto-thermopower detection of fractional quantum Hall states is more sensitive than resistivity measurements. We do this in the context of Bernal-stacked bilayer graphene and highlight several even-denominator states at a relatively low magnetic field. These capabilities of thermopower measurements support the interest in fractional quantum Hall states for finding quasiparticles with non-Abelian statistics and elevate bilayer graphene as a promising platform for achieving this. Fractional quantum Hall states can be fragile, meaning that they are difficult to probe using electrical transport measurements. Now, thermal transport is shown to be a more sensitive technique for investigating these states.