Transverse Thermoelectric Conductivity of Bilayer Graphene in Quantum Hall Regime

We performed electric and thermoelectric transport measurements of bilayer graphene in a magnetic field up to 15 Tesla. The transverse thermoelectric conductivity ${\alpha }_{\mathrm{x}\mathrm{y}}$, determined from four transport coefficients, attains a peak value of ${\alpha }_{\mathrm{x}\mathrm{y},\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}$ whenever chemical potential lies in the center of a Landau level. The temperature dependence of $\rm\alpha_{xy, peak}$isdictatedbythedisorderwidth$\rm W_L$\mathrm{.}For$\rm k_BT/W_L\leq$0.2,$\rm\alpha_{xy, peak}$isnominallylinearintemperature,whichgives$\rm\alpha_{xy,peak}/T=0.19 \pm 0.03 n A/K^2$ independent of the magnetic field, temperature and Landau Level index. At ${\mathrm{k}}_{\mathrm{B}}\mathrm{T}\mathrm{/}{\mathrm{W}}_{\mathrm{L}}\ge$0.5, ${\alpha }_{\mathrm{x}\mathrm{y},\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{k}}$ saturates to a value close to the predicted universal value of $4\times (\mathrm{l}\mathrm{n}2){\mathrm{k}}_{\mathrm{B}}\mathrm{e}\mathrm{/}\mathrm{h}$ according to the theory of Girvin and Jonson. We remark that an anomaly is found in ${\alpha }_{\mathrm{x}\mathrm{y}}$ near the charge neutral point, similar to that in single-layer graphene