Coupling of Higgs and Leggett modes in non-equilibrium superconductors.
Coupling of Higgs and Leggett modes in non-equilibrium superconductors.
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DOI：
10.1038/ncomms11921
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发表时间：
2016-06-21
影响因子：
16.6
通讯作者：
Schnyder AP
中科院分区：
文献类型：
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作者：
Krull H;Bittner N;Uhrig GS;Manske D;Schnyder AP
在平衡系统中，振幅和相位集体模式是解耦的，因为它们是相互正交的激励。通过线性响应测量直接检测这些希格斯和莱格特集体模式是不可能的，因为它们不直接耦合到电磁场。在这项工作中，使用精确的数值模拟，我们表明的情况下，两个间隙超导体，光泵浦探测实验激发希格斯和莱格特模式的平衡。我们发现，这种非绝热激发过程中引入了强烈的集体模式之间的相互作用，这是不存在的平衡。此外，我们提出了一种类型的泵浦探测实验，它允许探测和相干控制的希格斯和莱格特模式，从而直接的序参量。这些发现超出了双带超导体的范围，适用于量子材料中的一般集体模式。 在平衡系统中，振幅和相位的集体模式是解耦的，限制了对相关材料中竞争顺序的理解。在这里，Krull等人报告说，非绝热泵浦脉冲可以在Leggett和Higgs模式之间引起复杂的耦合，提供了一种在非平衡条件下耦合集体模式的方法。
In equilibrium systems amplitude and phase collective modes are decoupled, as they are mutually orthogonal excitations. The direct detection of these Higgs and Leggett collective modes by linear-response measurements is not possible, because they do not couple directly to the electromagnetic field. In this work, using numerical exact simulations we show for the case of two-gap superconductors, that optical pump–probe experiments excite both Higgs and Leggett modes out of equilibrium. We find that this non-adiabatic excitation process introduces a strong interaction between the collective modes, which is absent in equilibrium. Moreover, we propose a type of pump–probe experiment, which allows to probe and coherently control the Higgs and Leggett modes, and thus the order parameter directly. These findings go beyond two-band superconductors and apply to general collective modes in quantum materials. Collective modes of amplitude and phase are decoupled in equilibrium systems, limiting the understanding of competing orders in correlated material. Here, Krull et al. report that a non-adiabatic pump pulse can induce an intricate coupling between Leggett and Higgs modes, providing a way to couple collective modes in non-equilibrium condition.