Sharp quantum Hall edges: Experimental realizations of edge states without incompressible strips

Experimental results of sharp edge potentials in the quantum Hall (QH) regime of a two-dimensional electron system are presented. First the general QH edge state picture is reviewed, including recent theory which explains the importance of incompressible strips at the sample edge. Then two sharp edge geometries are presented where incompressible strips are predicted to vanish below the scale of the magnetic length: T-junction edge tunneling devices and L-junction bent quantum wells. Tunnel spectroscopy in the T-junction device directly measures the real space position of the edge state orbit centers, verifying an almost ideal sharp edge confinement and providing evidence that incompressible strips vanish in such a potential. Conduction along the junction of the L-sample is presented, revealing unconventional temperature and voltage dependence along a unique type of QH boundary. Hartree calculations explain how this behavior can result from the sharp non-planar confinement potential which is not possible to realize either in planar systems or at soft-confinement boundaries.