Thermopower Measurements on Bilayer Graphene in the Quantum Hall Regime

Thermopower is a direct and sensitive probe of the entropy associated with charge carriers, including fractional quasiparticles, in a system. In particular, thermopower measurements on 2D electron gases, including both GaAs and graphene, have demonstrated quantized thermoelectric conductivity in the quantum hall (QH) regime, as predicted by Girvin and Jonson[1][2]. Attempts have also been made to measure even-denominator fractional QH states in GaAs, where theory predicts that the filling fraction dependence of thermopower can provide evidence for the possible non-Abelian nature of the ground state[3][4]. The weak electron-phonon coupling in graphene provides an advantage over GaAs by reducing the conflating effects of phonon drag to the thermopower measurements. We will discuss progress and challenges in thermopower measurements on high-quality, dual-encapsulated Bernal bilayer graphene in the symmetry-broken integer and fractional QH regimes.

[1] Bayot et al. PRB 52, 12 (1995) [2] Checkelsky, Ong PRB, 80, 081413 (2009) [3] Chickering et al., PRB, 81, 245319 (2010) [4] Yang, Halperin, PRB, 79, 115317 (2009)