Magneto Transport and Quantum Effects in Electron Systems

本课题主要研究成果如下：(1)有机导体中的角相关磁阻振荡（ADMRO）效应。在有机导体（BEDT-TTG）_2KHg(SCN)_4和（BEDT-TTG）_2NH_4Hg(SCN)_4中观察到角相关振荡磁电阻。我们通过高磁场下样品的两轴旋转对角依赖性进行了精确测量，以澄清后者系统中的ADMRO是由调制的圆柱形费米面产生的标准ADMRO，而后者则归因于一对开放的费米片。我们还进行了模型计算，定量地再现了后者系统的ADMRO轨迹。(2)合成层状金属—sbcl_5插层石墨中的ADMRO效应我们也观察到了插层石墨中的ADMRO效应。ADMRO和Shubnikov-de Haas效应的分析是重建费米表面的有力手段，众所周知，由于区域折叠效应和磁击穿效应，费米表面在该系统中是复杂的。(3) GaAs/AlGaAs超晶格定制费米表面的ADMRO效应。我们在GaAs/AlGaAs超晶格中设计并制作了圆柱形费米表面，并证明了ADMRO在面外电阻率中发生得最为明显。(4)调制磁场中的磁输运。从理论上分析了一维调制磁场对二维电子气的影响。我们用铁磁性物质制成栅极，进行了实验尝试。

The following are the main research accomplishments of this project :(1)Angular dependent magnetoresistance oscillation(ADMRO) effect in organic conductors.Angular dependent oscillatory magnetoresistance has been observed in organic conductors, (BEDT-TTG)_2KHg(SCN)_4 and (BEDT-TTG)_2NH_4Hg(SCN)_4. We have performed precise measurements of the angular dependence by two-axis rotation of samples in high magnetic fields to clarify that the ADMRO in the latter system is a standard one arising form a modulated cylindrical Fermi surface, while that in the latter is attributed to a pair of open Fermi sheet. We have also made a model calculation which reproduced the ADMRO traces of the latter system quantitatively.(2)ADMRO effect in synthetic layred metal --- SbCl_5-intercalated graphiteWe have also observed the ADMRO in intercalated graphite. Analysis of both the ADMRO and the Shubnikov-de Haas effect powerful means of reconstruction of the Fermi surface, which is known to be complex in this system due to zone folding effect and magnetic breakdown effect.(3)ADMRO effect in tailored Fermi surface of GaAs/AlGaAs superlattice.We have designed and fabricated cylindrical Fermi surface in GaAs/AlGaAs superlattice and demonstrated that the ADMRO occurs most distinctly in the out-of-plane resistivity.(4)Magnetotransport in modulated magnetic field.We have theoretically analyzed the effect of one-dimensionally modulated magnetic field on two-dimensional electron gas. We have made an experimental attempt by use of a grid gate made of ferromagnetic substances.