Behavior of Composite Fermions and the Stripe Phase Subjected to Short-Period Periodic Potential or Magnetic Field Modulation

点击翻译按钮获取中文摘要

We have experimentally investigated the properties of short period (〜100 nm) unidirectional lateral superlattices in a magnetic field at low temperatures. Unidirectional lateral superlattice samples equipped with a back gate to control the electron density n_e have been fabricated. With these samples, we observed anisotropic magnetoresistance at high Landau levels, which was attributable to the response of the theoretically-predicted stripe phase (a charge density wave state) to the external modulation. We also found an unusual hysteretic behavior accompanying the variation of n_e.Transport properties of electrons at low magnetic fields have been explored in detail, which can be mapped to the properties of composite Fermions at low effective magnetic fields. We have found that the origin of the well-known positive magnetoresistance is mainly attributable to the drift velocity resulting from incompleted cyclotron orbits, and that the contribution of the channeled orbit is small, in contrast to what have been believed for some fifteen years.We have uncovered a new class of small-amplitude magnetoresistance oscillation superposed on the positive magnetoresistance. The new oscillation has been attributed, from its dependence on the period of the modulation and on n_e, to the geometric resonance between the modulation period and the width of the "open orbit" resulting from the Bragg reflection by the superlattice.We have studied the dependence of the modulation amplitude on n_e quantitatively, and have elucidated the effect of finite thickness of the two-dimensional electron gas on the amplitude.