Transverse Thermoelectric Conductivity of Bilayer Graphene in Quantum Hall Regime

Abstract

We performed electric and thermoelectric transport measurements of bilayer graphene in a magnetic field up to 15 Tesla. The transverse thermoelectric conductivity ${\alpha }_{\mathrm{xy}}$, determined from four transport coefficients, attains a peak value of ${\alpha }_{\mathrm{xy},\mathrm{peak}}$ whenever chemical potential lies in the center of a Landau level. The temperature dependence of ${\alpha }_{\mathrm{xy},\mathrm{peak}}$ is dictated by the disorder width ${\mathrm{W}}_{\mathrm{L}}$. For ${\mathrm{k}}_{\mathrm{B}}T/{\mathrm{W}}_{\mathrm{L}}\le$0.2, ${\alpha }_{\mathrm{xy},\mathrm{peak}}$ is nominally linear in temperature, which gives ${\alpha }_{\mathrm{xy},\mathrm{peak}}/T=0.19\pm 0.03nA/{\mathrm{K}}^2$ independent of the magnetic field, temperature and Landau Level index. At ${\mathrm{k}}_{\mathrm{B}}T/{\mathrm{W}}_{\mathrm{L}}\ge$0.5, ${\alpha }_{\mathrm{xy},\mathrm{peak}}$ saturates to a value close to the predicted universal value of $4\times (ln2){\mathrm{k}}_{\mathrm{B}}e/h$ according to the theory of Girvin and Jonson. We remark that an anomaly is found in ${\alpha }_{\mathrm{xy}}$ near the charge neutral point, similar to that in single-layer graphene

12 pages, 4 figures, version 2