Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering

March 30, 2016

Figure 1: (a) The measured conductivity σ (a) and (b) TEP S as functions of temperature T and gate voltage Vg in the sample with lowest disorder in this experiment (sample D3). At T=20, 130, and 250 K (horizontal dash cuts), σ(Vg) and S(Vg) (solid curves) are shown in the overlaid graphs where the temperature cuts indicate σ or S=0. The upper inset shows a typical device image where the scale bar corresponds to 2  μm. [Reprinted with permission from APS ©2016.]

A new Physical Review Letter by Prof. Philip Kim and colleagues from Columbia University, Rice University, and National Institute for Material Science, Tsukuba, Japan, reports the enhancement of the thermoelectric power (TEP) in graphene with extremely low disorder. The authors observe that, at high temperature, the TEP is substantially larger than the prediction of the Mott relation, approaching to the hydrodynamic limit due to strong inelastic scattering among the charge carriers. However, closer to room temperature the inelastic carrier–optical-phonon scattering becomes more significant and limits the TEP below the hydrodynamic prediction.

See Fereshte Ghahari, Hong-Yi Xie, Takashi Taniguchi, Kenji Watanabe, Matthew S. Foster, and Philip Kim, "Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering," Phys. Rev. Lett. 116, 136802 | DOI: http://dx.doi.org/10.1103/PhysRevLett.116.136802