MULTIPLE SUBBAND CROSSING IN A ONE-DIMENSIONAL HOLE GAS WITH ENHANCEDG-FACTORS

We have measured the transport properties of one-dimensional ballistic constrictions defined in a two-dimensional hole gas. The conductance quantization of the constrictions switches between even and odd multip les of e(2)/h as a function of a parallel magnetic field, as spin-spli tting causes the subbands of the 1D channel to cross repeatedly. The i n-plane g-factors of the 1D subbands are measured from the low field d ata. We find them to increase as the number of occupied 1D subbands de creases and attribute this enhancement of the g-factor to Coulomb inte ractions. The quantization at high fields shows that the subbands have crossed four times; in this regime the system is highly magnetized an d exchange effects should be of particular importance. (C) 1998 Elsevi er Science B.V. All rights reserved.