Observation of e²/h conductance steps in a side-gate point contact on In_0.75Ga_0.25As/In_0.75Al _0.25As heterostructure

In 1996, it was suggested by K. J. Thomas et al. (Phys. Rev. Lett. 77,135 (1996)) that 0.7(2e²/h) conductance structure in Quasi-1 DEG (Q1DEG) at GaAs/AlGaAs heterostructure might be related to spin polarization at zero magnetic field. We have recently studied spontaneous spin-splitting in the 2DEGs formed at normal metamorphic In_0.75Ga_0.25As/n _0.75Al_0.25As heterojunctions grown on GaAs substrates and obtained the value of ≲10 meV as the zero-field splitting at Fermi level (Y. Sato et al., J. Appl. Phys. 89, 8017 (2001)). In this work, we attempted to observe spin-related phenomena in this heterojunction Q1DEGs at zero magnetic field. We observed e²/h conductance steps in low electron concentration side-gate point contact.