Coherent cyclotron motion beyond Kohn's theorem
Coherent cyclotron motion beyond Kohn's theorem
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DOI：
10.1038/nphys3559
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发表时间：
2016-02-01
期刊：
影响因子：
19.6
通讯作者：
Kira, M.
中科院分区：
文献类型：
--
作者：
Maag, T.;Bayer, A.;Kira, M.
在固体中，带电粒子的高密度使得多体相互作用成为控制光学和电子学的普遍原理（1-12）。然而，Walter Kohn在1961年发现朗道量子化电子的回旋共振与电子之间看似不可避免的库仑相互作用无关（2）。虽然这个令人惊讶的定理已经在复杂的量子现象（13-15）中得到了利用，例如超强光-物质耦合（16），超辐射（17）和相干控制（18），但完全没有非线性排除了许多有趣的可能性，例如量子逻辑协议（19）。在这里，我们使用强烈的太赫兹脉冲驱动的回旋响应的二维电子气超出科恩定理的保护范围。非谐朗道阶梯攀登和不同的太赫兹四和六波混频签名发生，我们的理论联系到电子和带正电的离子背景之间的动态库仑效应。科恩定理的这一新的背景揭示了以前无法达到的朗道电子的内部自由度，为电子的超快量子控制开辟了新的领域。
In solids, the high density of charged particles makes many-body interactions a pervasive principle governing optics and electronics(1-12). However, Walter Kohn found in 1961 that the cyclotron resonance of Landau-quantized electrons is independent of the seemingly inescapable Coulomb interaction between electrons(2). Although this surprising theorem has been exploited in sophisticated quantum phenomena(13-15), such as ultrastrong light-matter coupling(16), superradiance(17) and coherent control(18), the complete absence of nonlinearities excludes many intriguing possibilities, such as quantum-logic protocols(19). Here, we use intense terahertz pulses to drive the cyclotron response of a two-dimensional electron gas beyond the protective limits of Kohn's theorem. Anharmonic Landau ladder climbing and distinct terahertz four-and six-wave mixing signatures occur, which our theory links to dynamic Coulomb effects between electrons and the positively charged ion background. This new context for Kohn's theorem unveils previously inaccessible internal degrees of freedom of Landau electrons, opening up new realms of ultrafast quantum control for electrons.