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arXiv 2106.12640cond-mat.dis-nnphysics.optics
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非厄米无序系统中的波激发和动力学

Wave Excitation and Dynamics in Non-Hermitian Disordered Systems

Yiming Huang, Yuhao Kang, Azriel Z. Genack

摘要:

在散射矩阵为幺正的无损耗开放系统中,波传播的动态和稳态方面是紧密相连的。于是,在介质中激发的能量、维格纳时间延迟和态密度之间存在等价性。但是,这些等价在物质损失或收益出现时就消失了。本文采用微波测量、数值模拟和理论分析的方法,揭示了内场、透射率、透射时间、停留时间、总激发能和态密度随损耗和增益的变化关系,以及它们对维数和谱重叠的依赖性。激发的总能量等于停留时间。在1D中,平均传输时间与损耗、增益和散射强度无关。然而,在更高的维度中,平均传输时间随着损耗、散射强度和信道数而下降,并且随着增益而增加。它是与传输矩阵的零点以及极点相关联的洛伦兹函数的总和。这赋予了传输零点强大的拓扑特性:在酉介质中,零点要么单独出现在实轴上,要么作为复频率平面上的共轭对。在弱吸收介质中,最低传输本征通道的传输时间的频谱是由于传输零点加上由于远离谐振极点的背景而引起的洛伦兹线的和。复平面中的传输零点的平均密度是从具有吸收的平均传输时间的下降中找到的,因为零点被扫入复频率平面的下半部分。我们发现,在复杂的频率平面的极点和零点的配置提供了一个框架,了解和控制波在非厄米系统的传播。

英文摘要:

Dynamic and steady state aspects of wave propagation are deeply connected in lossless open systems in which the scattering matrix is unitary. There is then an equivalence among the energy excited within the medium, the Wigner time delay, and the density of states. But these equivalences fall away in the presence of material loss or gain. In this paper, we use microwave measurements, numerical simulations, and theoretical analysis to discover the changing relationships among the internal field, transmission, transmission time, dwell time, total excited energy, and the density of states in with loss and gain, and their dependence upon dimensionality and spectral overlap. The total energy excited is equal to the dwell time. In 1D, the average transmission time is independent of loss, gain, and scattering strength. In higher dimensions, however, the average transmission time falls with loss, scattering strength and channel number, and increases with gain. It is the sum over Lorentzian functions associated with the zeros as well as the poles of the transmission matrix. This endows transmission zeros with robust topological characteristics: in unitary media, zeros occur either singly on the real axis or as conjugate pairs in the complex frequency plane. In weakly absorbing media, the spectrum of the transmission time of the lowest transmission eigenchannel is the sum of Lorentzians due to transmission zeros plus a background due to far-off-resonance poles. The average density of transmission zeros in the complex plane is found from the fall of the average transmission time with absorption as zeros are swept into the lower half of the complex frequency plane. We show that the disposition of poles and zeros in the complex frequency plane provides a framework for understanding and controlling wave propagation in non-Hermitian systems.

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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