EXPERIMENTAL STUDIES OF THE PHASE COHERENCE IN THE QUANTUM HALL-EFFECT REGIME

We study transport coefficients of Al0.3Ga0.7As/GaAs heterostructure H all bars with two Schottky cross gates placed separately leaving a 100 mu m-long gate-free region. When the gate-free region is in a quantum Hall effect state at low temperatures, the electron states in the sep arated gated regions strongly interfere with each other, being mediate d by the edge states in the gate-free region. The experimental results indicate that the phase coherence of edge states extends over a dista nce far larger than 200 mu m at 25 mK. (C) 1997 Elsevier Science Ltd.