Back-gated point contact

In this study, we fabricated split gates on a back-gated undoped heterostru cture to perform transport measurements on a quantum point contact (QPC). U sing this back-gated QPC system, we obtained clear quantized conductance pl ateaus over a wide range of electron densities (1.2 x 10(15) m(-2) to 3.3 x 10(15) m(-2)) without being affected by imperfections. We also observed a clear 0.7 G(0) (G(0) = 2e(2)/h) anomaly. The shape of the anomaly varies wi th electron density. Furthermore, the conductance value at which this anoma ly appears is not precisely 0.7 Go but changes with electron density.