▎ 摘 要
Transport through edge channels is responsible for conduction in quantum Hall (QH) phases. Robust quantized values of charge and thermal conductances dictated by bulk topology appear when equilibration processes become dominant. We report on measurements of electrical and thermal conductances of integer and fractional QH phases, realized in hexagonal boron nitride encapsulated graphite-gated bilayer graphene devices for both electron and hole doped sides with different valley and orbital symmetries. Remarkably, for complex edges at filling factors nu = 5/3 and 8/3, closely related to the paradigmatic hole-conjugate nu = 2/3 phase, we find quantized thermal conductance whose values (3 kappa T-0 and 4 kappa T-0, respectively where kappa T-0 is the thermal conductance quantum) are markedly inconsistent with the values dictated by topology (1 kappa T-0 and 2 kappa T-0, respectively). The measured thermal conductance values remain insensitive to different symmetries, suggesting its universal nature. Our findings are supported by a theoretical analysis, which indicates that, whereas electrical equilibration at the edge is established over a finite length scale, the thermal equilibration length diverges for strong electrostatic interaction. Our results elucidate the subtle nature of crossover from coherent, mesoscopic to topology-dominated transport.