Electronic Thermal Transport in h-BN/Graphene/h-BN heterostructures

Using a senstive differential electro-thermal measurement technique, we observe that the Lorenz number for the electornic thermal conductivity of h-BN/graphene/h-BN heterostructures is considerablly lower than the Sommerfeld value in the single-band regime at room temperatrue and below. In the bi-polar regime near the Dirac point, a Lorenz peak well above the Sommerfeld value is observed at room temperatrue, and decreases with decreasing temperature. The deviation from the Wiedemann-Franz law and its temperature dependence provide insight into the unique transport behavior of Dirac Fermions in this system.