Transport and level anticrossing in strongly coupled double quantum wells with in-plane magnetic fields

Interesting in-plane low-temperature transport properties are proposed in doped thin double quantum wells in an in-plane magnetic field (B). The density of states diverges at a saddle point (SP). The SP is formed at the lower edge of the partial energy gap at a sufficiently high B due to an anticrossing of the two displaced energy-dispersion parabolas. At high carrier densities, the conductance (G) shows a maximum when the upper branch is emptied and a minimum at a higher B=${\mathit{B}}_{\min }$ when the Fermi level lies at the SP. These features are confirmed by recent data. At low densities (i.e., with only the lower branch populated), only a G minimum is predicted to occur. The electron-diffusion thermopower diverges both above and below ${\mathit{B}}_{\min }$ with opposite signs. The correlation between the recently observed tunneling G and the in-plane G is discussed.