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arXiv 1101.4852cond-mat.dis-nn
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自旋无序引发的安德森局域化--及其在Eu_xCa_(1-x)B_6中的应用

Anderson Localization Triggered by Spin Disorder---with an Application to Eu_x Ca_1-x B_6

Daniel Egli, Jürg Fröhlich, Hans-Rudolf Ott

摘要:

研究了一类具有随机塞曼相互作用的单粒子薛定谔算符的安德森局域化现象。这些算子产生如下:静态自旋随机地放置在一个简单的立方晶格的网站上,根据一个网站渗透过程与密度x和相互耦合的铁磁。在这些自旋的导带中的电子的散射由源自间接交换的随机塞曼相互作用项描述。严格地表明,对于低于逾渗阈值的正值x,带边附近的单电子薛定谔算子的谱是致密的纯点,并且相应的本征函数是指数定域的。在弱的外部磁场H中,带边缘附近的局部化持续存在,但随着H的增加,局部化逐渐消失。我们的研究结果使我们预测的现象,巨大的(负)磁电阻和莫特过渡的存在,H和/或x的增加。我们的分析是由有关磁性合金Eu_xCa_(1-x)B_6的实验结果直接激发的。

英文摘要:

The phenomenon of Anderson localization is studied for a class of one-particle Schrödinger operators with random Zeeman interactions. These operators arise as follows: Static spins are placed randomly on the sites of a simple cubic lattice according to a site percolation process with density x and coupled to one another ferromagnetically. Scattering of an electron in a conduction band at these spins is described by a random Zeeman interaction term that originates from indirect exchange. It is shown rigorously that, for positive values of x below the percolation threshold, the spectrum of the one-electron Schrödinger operator near the band edges is dense pure-point, and the corresponding eigenfunctions are exponentially localized. Localization near the band edges persists in a weak external magnetic field, H, but disappears gradually, as H is increased. Our results lead us to predict the phenomenon of colossal (negative) magnetoresistance and the existence of a Mott transition, as H and/or x are increased. Our analysis is motivated directly by experimental results concerning the magnetic alloy Eu_x Ca_1-x B_6.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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