The quantum of thermal conductance of ballistic (collisionless) one-dimensional channels is a unique fundamental constant1. Although the quantization of the electrical conductance of one-dimensional ballistic conductors has long been experimentally established2, demonstrating the quantization of thermal conductance has been challenging as it necessitated an accurate measurement of very small temperature increase. It has been accomplished for weakly interacting systems of phonons3,4, photons5 and electronic Fermi liquids6,7,8; however, it should theoretically also hold in strongly interacting systems, such as those in which the fractional quantum Hall effect is observed. This effect describes the fractionalization of electrons into anyons and chargeless quasiparticles, which in some cases can be Majorana fermions2. Because the bulk is incompressible in the fractional quantum Hall regime, it is not expected to contribute substantially to the thermal conductance, which is instead determined by chiral, one-dimensional edge modes. The thermal conductance thus reflects the topological properties of the fractional quantum Hall electronic system, to which measurements of the electrical conductance give no access9,10,11,12. Here we report measurements of thermal conductance in particle-like (Laughlin–Jain series) states and the more complex (and less studied) hole-like states in a high-mobility two-dimensional electron gas in GaAs–AlGaAs heterostructures. Hole-like states, which have fractional Landau-level fillings of 1/2 to 1, support downstream charged modes as well as upstream neutral modes13, and are expected to have a thermal conductance that is determined by the net chirality of all of their downstream and upstream edge modes. Our results establish the universality of the quantization of thermal conductance for fractionally charged and neutral modes. Measurements of anyonic heat flow provide access to information that is not easily accessible from measurements of conductance.
We acknowledge the help and advice of R. Sabo, I. Gurman, N. OfeK, H.-K. Choi and D. Mahalu. M.H. acknowledges the European Research Council under the European Community’s Seventh Framework Programme, grant agreement number 339070, the partial support of the Minerva Foundation, grant number 711752, and, together with V.U., the German Israeli Foundation (GIF), grant number I-1241-303.10/2014, and the Israeli Science Foundation (ISF). A.S. and Y.O. acknowledge the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013)/ERC, grant agreement number 339070, and the Israeli Science Foundation, ISF agreement number 13335/16. Y.O. acknowledges CRC 183 of the DFG. D.E.F. acknowledges support by the NSF under grant number DMR-1205715.