arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1408.1972cond-mat.mes-hallphysics.opticsquant-ph
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自由电子朗道态的动力学成像

Imaging the dynamics of free-electron Landau states

P. Schattschneider, Th. Schachinger, M. Stöger-Pollach, S. Löffler, A. Steiger-Thirsfeld, K. Y. Bliokh, F. Nori

摘要:

磁场中电子的朗道能级和态是凝聚态物理中量子霍尔效应和相关效应的基本量子实体。然而,朗道波函数的实空间性质和观测仍然难以捉摸。在这里,我们报告的第一个真实空间观测的朗道态和内部旋转动力学的自由电子。在准均匀磁场中,使用纳米尺寸的电子涡旋束产生具有不同量子数的态,电子涡旋束的半径被选择为与朗道态的腰部相匹配。沿传输方向扫描光束,我们重建了角频率~100 GHz的朗道波函数的旋转动力学。我们观察到具有不同方位角量子数的朗道模属于三类,其特征在于分别以零、拉莫尔和回旋频率旋转。这与经典电子的均匀回旋旋转形成鲜明对比,并且与最近的理论预测完全一致。

英文摘要:

Landau levels and states of electrons in a magnetic field are fundamental quantum entities underlying the quantum-Hall and related effects in condensed matter physics. However, the real-space properties and observation of Landau wave functions remain elusive. Here we report the first real-space observation of Landau states and the internal rotational dynamics of free electrons. States with different quantum numbers are produced using nanometer-size electron vortex beams, with a radius chosen to match the waist of the Landau states, in a quasi-uniform magnetic field. Scanning the beams along the propagation direction, we reconstruct the rotational dynamics of the Landau wave functions with angular frequency ~100 GHz. We observe that Landau modes with different azimuthal quantum numbers belong to three classes, which are characterized by rotations with zero, Larmor, and cyclotron frequencies, respectively. This is in sharp contrast to the uniform cyclotron rotation of classical electrons, and in perfect agreement with recent theoretical predictions.

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