Novel magnetic-field-induced minigap and transport in coupled double quantum wells

A review is given of recent theoretical and experimental work on in-plane electron transport in strongly coupled double quantum wells (QWs) in the presence of an in-plane magnetic field B{sub {parallel}} {parallel} x. This system displays unusual electronic and transport properties arising from a partial minigap ({approximately} a few meV) formed in the transverse in-plane direction k{sub y} {perpendicular} B{sub {parallel}} in k-space due to the anticrossing of the two QW dispersion curves displaced relative to each other by {Delta}k{sub y} {proportional_to} B{sub {parallel}}. Sweeping B{sub {parallel}} moves the minigap through the Fermi level ({mu}), deforming the Fermi surface from a two-component surface (with one orbit inside the other) to a single-orbit surface, and then back to a two-separated-orbit structure, accordingly as {mu} lies above, inside, and below the gap, respectively. The authors show that the density of states develops a sharp van Hove singularity at the lower gap edge, while transport properties such as the in-plane conductance and the cyclotron mass show sharp B{sub {parallel}}-dependent structures as {mu} passes through the gap edges