PHASE COHERENCE OF EDGE STATES OVER MACROSCOPIC LENGTH SCALES

Phase coherence of edge states in the integer quantum-Hall states is s tudied through the observation of interference effects occurring betwe en two macroscopically separated gated regions of a two-dimensional el ectron gas (2DEG) system. When a 2DEG density in the two-gated regions varies simultaneously while the 2DEG regions without the gates are ma intained in an integer quantum-Hall state, the transition width betwee n successive integer quantum-Hall states significantly narrows as comp ared to the case when only one of the two gates is biased. This sugges ts coherent interference between the electron states in the separated two gated regions. By externally introducing partial phase-breaking in to the electron system by weakly coupling the system to the Ohmic cont act, the size of the phase coherence length of edge states is estimate d to be 5.4 mm at a temperature of 20 mK and a magnetic field of 3.3 T . (C) 1998 Elsevier Science B.V. All rights reserved.