Conductance quantization and the 0.7x2e2/h conductance anomaly in   one-dimensional hole systems
  We have studied ballistic transport in a 1D channel formed using surface gate techniques on a back-gated, high-mobility, bilayer 2D hole system. At millikelvin temperatures, robust conductance quantization is observed in the quantum wire formed in the top layer of the bilayer system, without the gate instabilities that have hampered previous studies of 1D hole systems. Using source drain bias spectroscopy, we have measured the 1D subband spacings, which are 5-10 times smaller than in comparable GaAs electron systems, but 2-3 times larger than in previous studies of 1D holes. We also report the first observation of the anomalous conductance plateau at G = 0.7 x 2e2/h in a 1D hole system. 
R. Danneau, W.R. Clarke, O. Klochan, A.P. Micolich, A.R. Hamilton and   M.Y. Simmons, M. Pepper and D.A. Ritchie