Quantization of Heat Flow in Fractional Quantum Hall States

Quantum mechanics sets an upper bound on the amount of charge flow as well as on the amount of heat flow in ballistic one-dimensional channels. The two relevant upper bounds, that combine only fundamental constants, are the quantum of the electrical conductance, G_e=e²/h, and the quantum of the thermal conductance, G_th=π²k_B²T/3h. Remarkably, the latter does not depend on particles charge; particles exchange statistics; and even the interaction strength among the particles.
However, unlike the relative ease in determining accurately the quantization of the electrical conductance, measuring accurately the thermal conductance is more challenging. The universality of the latter quantization was demonstrated for weakly interacting particles; such as, phonons [1], photons [2], and electronic Fermi-liquids [3].
I will describe our recent experiments of heat flow in a strongly interacting system of 2D electrons in the FQHE regime. I will focus on particle-like states (Laughlin’s states, v<½), and on the more complex, hole-conjugate states (½<v<1) [4]. More recently, we extended our studies to fractional states in the first-excited Landau level (2<v<3). In particular, in the v=5/2 state we find a deviation from the quantization of the thermal conductance, suggesting a non-abelian behavior [5].


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