Transverse thermoelectric conductivity of bilayer graphene in the quantum Hall regime

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