  We demonstrate a direct approach to investigate heat transport in the
fractional quantum Hall regime. At filling factor of 4/3, we inject power at
quantum point contacts and detect the related heating from the activated
current through a quantum dot. The experiment reveals a chargeless heat
transport from a significant heating that occurs upstream of the power
injection point, in the absence of a concomitant electrical current. By tuning
in-situ the edge path, we show that the chargeless heat transport does not
follow the reverse direction of the electrical current path along the edge.
This unexpected heat conduction demonstrates a novel aspect, yet to be
elucidated, of the physics in fractional quantum Hall systems.
