Acoustic non-Hermitian skin effect from twisted winding topology

Zhang, Li; Yang, Yihao; Ge, Yong; Guan, Yijun; Chen, Qiaolu; Yan, Qinghui; Chen, Fujia; Xi, Rui; Ding, Jia; Yuan, Shouqi; Sun, Hong-xiang; Chen, Hongsheng; Zhang, Baile

doi:10.21203/rs.3.rs-449338/v1

Cited by 7 publications

(8 citation statements)

References 29 publications

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“…Non-Hermitian skin effect.-Closely related to the chiral coupling in optics and magnetism as reviewed here is the "short-range asymmetric coupling" in the non-Hermitian skin effect, which refers to the localization of bulk states at a boundary of a dynamic system [395][396][397][398][399][400][401][402][403][404][405][406]. This effect has been observed in systems with relatively short-range interactions [407,408], e.g., in photonic lattice [409], electric circuits [410], and mechanical metamaterials [411].…”

Section: Spin Skin Effectmentioning

confidence: 99%

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Chen¹,

Luo²,

Bauer³

2022

Preprint

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Chirality or handedness is a digital relation between three vectors that distinguishes an object from its mirror image, such as the spread fingers of the right and left hand. The chirality of ground state magnetic textures defined by the vectors of magnetization, its gradient, and an electric field from broken inversion symmetry can be fixed by a strong relativistic spin-orbit interaction. This review focuses on the chirality observed in the excited states of the magnetic order, dielectrics, and conductors that hold transverse spins when they are evanescent. Even without any relativistic effect, the transverse spin of the evanescent waves are locked to the momentum and the surface normal of their propagation plane. This chirality thereby acts as a generalized spin-orbit interaction, which leads to the discovery of various chiral interactions between magnetic, phononic, electronic, photonic, and plasmonic excitations in spintronics that mediate the excitation of quasiparticles into a single direction, leading to phenomena such as chiral spin and phonon pumping, chiral spin Seebeck, spin skin, magnonic trap, magnon Doppler, and spin diode effects. Intriguing analogies with electric counterparts in the nano-optics and plasmonics exist. After a brief review of the concepts of chirality that characterize the ground state chiral magnetic textures and chirally coupled magnets in spintronics, we turn to the chiral phenomena of excited states. We present a unified electrodynamic picture for dynamical chirality in spintronics in terms of generalized spin-orbit interaction and compare it with that in nano-optics and plasmonics. Based on the general theory, we subsequently review the theoretical progress and experimental evidence of chiral interaction, as well as the near-field transfer of the transverse spins, between various excitations in magnetic, photonic, electronic and phononic nanostructures at GHz time scales. We provide a perspective for future research before concluding this article.

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Section: Spin Skin Effectmentioning

confidence: 99%

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Chen¹,

Luo²,

Bauer³

2022

Preprint

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“…1d). The directionality and strength of the power imbalance across the array is dictated by the sign and value of the field parameter g. Recently, this type of lattice has been demonstrated in acoustic systems 10 , mechanical metamaterials 29,30 and electrical circuits 31,32 , and also proposed in elastic media 33 and cold atoms 20 . In optics, such lattices have been only implemented in synthetic dimensions, leading to the observation of light funneling with interface localization 12 , non-Hermitian bands with arbitrary winding numbers 13 , and complex-energy braiding 14 .…”

Section: Introductionmentioning

confidence: 99%

Complex skin modes in non-Hermitian coupled laser arrays

et al. 2022

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From biological ecosystems to spin glasses, connectivity plays a crucial role in determining the function, dynamics, and resiliency of a network. In the realm of non-Hermitian physics, the possibility of complex and asymmetric exchange interactions ($$\left| {\kappa _{ij}} \right| \ne \left| {\kappa _{ji}} \right|$$ κ i j ≠ κ j i ) between a network of oscillators has been theoretically shown to lead to novel behaviors like delocalization, skin effect, and bulk-boundary correspondence. An archetypical lattice exhibiting the aforementioned properties is that proposed by Hatano and Nelson in a series of papers in late 1990s. While the ramifications of these theoretical works in optics have been recently pursued in synthetic dimensions, the Hatano–Nelson model has yet to be realized in real space. What makes the implementation of these lattices challenging is the difficulty in establishing the required asymmetric exchange interactions in optical platforms. In this work, by using active optical oscillators featuring non-Hermiticity and nonlinearity, we introduce an anisotropic exchange between the resonant elements in a lattice, an aspect that enables us to observe the non-Hermitian skin effect, phase locking, and near-field beam steering in a Hatano–Nelson laser array. Our work opens up new regimes of phase-locking in lasers while shedding light on the fundamental physics of non-Hermitian systems.

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“…Origin of these localized skin modes is rooted in nontrivial topological winding of the bulk PBC spectral contour in complexenergy plane with respect to the interior OBC spectral points [8][9][10][11][12] . The interplay of topology, non-Hermiticity, and nonnormality is an active field of research both in theory and experiments [47][48][49][50][51][52][53][54] with far reaching practical consequences.…”

Section: Introductionmentioning

confidence: 99%

Topological directed amplification

Midya

2022

Preprint

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A phenomenon of topological directed amplification of certain initial perturbations is theoretically revealed to emerge in a class of asymptotically stable skin-effect photonic lattices described by nonnormal Toeplitz operators Hg with positive 'numerical ordinate' ω(Hg) > 0. Nonnormal temporal evolution, even in the presence of global dissipation, is shown to exhibit a counterintuitive transient phase of edge-state amplification-a behavior, drastically different from the asymptote, that spectral analysis of Hg fails to directly reveal. A consistent description of the effect is provided by the general tool of 'pseudospectrum', and a quantitative estimation of the maximum power amplification is provided by the Kreiss constant. A recipe to determine an optimal initial condition that will attain maximum amplification power is given by singular value decomposition of the propagator e −iHg t . Finally, it is predicted that the interplay between nonnormality and nonlinearity in a skin-effect laser array can exponentially enhance stable-emission power compared to a normal laser array.

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Acoustic non-Hermitian skin effect from twisted winding topology

Cited by 7 publications

References 29 publications

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Complex skin modes in non-Hermitian coupled laser arrays

Topological directed amplification

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