Effects of accidental microconstriction on the quantized conductance in long wires.pdfVIP

2 0 0 Effects of accidental microconstriction on the quantized 2 conductance in long wires n u A.A. Starikov†‡, I.I.Yakimenko†, K.-F. Berggren†, A.C. Graham§, J K.J. Thomas§, M. Pepper§, and M.Y. Simmons§ 1 † Department of Physics and Measurement Technology, Link¨oping University, S-581 83 Link¨oping, Sweden ] l ‡ Kirensky Institute of Physics, 660036, Krasnoyarsk, Russia l §Cavendish Laboratory, Madingley Road, a h Cambridge CB3 00HE, United Kingdom - s e Abstract. We have investigated the conductance of long quantum wires formed in GaAs/Al Ga As heterostructures. Using realistic fluctuation potentials from donor m x 1−x . layers we have simulated numerically the conductance of four different kinds of wires. t a While ideal wires show perfect quantization, potential fluctuations from random donors m may give rise to strong conductance oscillations and degradation of the quantization plateaux. Statistically there is always the possibility of having large fluctuations in a - d sample that may effectively act as a microconstriction. We therefore introduce microcon- n strictions in the wires by occasional clustering of donors. These microconstrictions are o found to restore the quantized plateaux. A sim