McMillan Stephen R, Harmon Nicholas J, Flatté Michael E
Optical Science and Technology Center, and Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA.
Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA.
Phys Rev Lett. 2020 Dec 18;125(25):257203. doi: 10.1103/PhysRevLett.125.257203.
We predict strong, dynamical effects in the dc magnetoresistance of current flowing from a spin-polarized electrical contact through a magnetic dopant in a nonmagnetic host. Using the stochastic Liouville formalism we calculate clearly defined resonances in the dc magnetoresistance when the applied magnetic field matches the exchange interaction with a nearby spin. At these resonances spin precession in the applied magnetic field is canceled by spin evolution in the exchange field, preserving a dynamic bottleneck for spin transport through the dopant. Similar features emerge when the dopant spin is coupled to nearby nuclei through the hyperfine interaction. These features provide a precise means of measuring exchange or hyperfine couplings between localized spins near a surface using spin-polarized scanning tunneling microscopy, without any ac electric or magnetic fields, even when the exchange or hyperfine energy is orders of magnitude smaller than the thermal energy.
我们预测，从自旋极化电接触流经非磁性主体中的磁性掺杂剂的电流，其直流磁电阻会产生强烈的动力学效应。使用随机刘维尔形式，当外加磁场与附近自旋的交换相互作用相匹配时，我们计算出直流磁电阻中明确的共振。在这些共振处，外加磁场中的自旋进动被交换场中的自旋演化抵消，从而为通过掺杂剂的自旋输运保留了一个动态瓶颈。当掺杂剂自旋通过超精细相互作用与附近原子核耦合时，也会出现类似特征。这些特征提供了一种精确的方法，即使在交换或超精细能量比热能小几个数量级的情况下，也能在没有任何交流电场或磁场的情况下，使用自旋极化扫描隧道显微镜测量表面附近局域自旋之间的交换或超精细耦合。
