Bulk elastic waves with unidirectional backscattering-immune topological states in a time-dependent superlattice

Swinteck, N.; Matsuo, Sadashige; Runge, Keith; Vasseur, J. O.; Lucas, Pierre; Deymier, Pierre A.

doi:10.1063/1.4928619

Cited by 128 publications

(103 citation statements)

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“…This special type of modulation has been studied in elastic and acoustic materials [9][10][11][12], whose nonreciprocal properties for the propagation of waves have been widely demonstrated. We will apply these ideas to the diffusion equation describing thermal waves in solids, and nonreciprocal thermal transport will be found.…”

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confidence: 99%

Nonreciprocal Thermal Material by Spatiotemporal Modulation

2018

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The thermal properties of a material with a spatiotemporal modulation, in the form of a traveling wave, in both the thermal conductivity and the specific heat capacity are studied. It is found that these materials behave as materials with an internal convectionlike term that provides them with nonreciprocal properties, in the sense that the heat flux has different properties when it propagates in the same direction or in the opposite one to the modulation of the parameters. An effective medium description is presented which accurately describes the modulated material, and numerical simulations support this description and verify the nonreciprocal properties of the material. It is found that these materials are promising candidates for the design of thermal diodes and other advanced devices for the control of the heat flow at all scales. DOI: 10.1103/PhysRevLett.120.125501 The research on materials with nonreciprocal thermal properties has received a great amount of attention in recent years. These materials have different propagation of thermal energy along two opposite directions. With the socalled thermal diode being the most immediate application of these structures [1], other devices and applications are easily envisioned, like thermal transistors and even logic circuits [2]. Nonreciprocal materials have been properly studied theoretically and experimentally at different scales [3][4][5][6], and it has been demonstrated that the realization of a nonreciprocal material requires the use of a combination of nonlinear and asymmetric structures [7]. However, the realization of nonreciprocal materials based on nonlinear elements limits their applicability, since nonlinearity does not occur at all temperatures and scales, so that we find that the rectification properties of the materials are efficient in only a short range of temperatures.In this context, metamaterials, which are artificially structured materials with a priori-designed properties, have overcome one of the major drawbacks of common materials, since their properties depend on the internal artificial structure and not on intrinsic properties of the constituent materials, which in turn allows us to decide at which scale, frequency, or temperature range we want to operate [8].Here, a special type of metamaterial is employed presenting nonreciprocal properties, which consists of a material where the thermal properties are functions of both space and time in a wavelike fashion. This special type of modulation has been studied in elastic and acoustic materials [9][10][11][12], whose nonreciprocal properties for the propagation of waves have been widely demonstrated. We will apply these ideas to the diffusion equation describing thermal waves in solids, and nonreciprocal thermal transport will be found.

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confidence: 99%

Nonreciprocal Thermal Material by Spatiotemporal Modulation

2018

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“…In contrast to the intensive theoretical studies of the topological elastic waves [31][32][33][34] , there is a lack of an experimental demonstration in the continuous structures. One of the main challenges is due to high modal densities of elastic waves in continuous-solid structures, preventing the formation of complete PnBGs with topologically distinct properties.…”

Section: Introductionmentioning

confidence: 99%

Topologically protected elastic waves in one-dimensional phononic crystals of continuous media

Kim¹,

Iwamoto²,

Arakawa³

2017

Appl. Phys. Express

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We report the design of silica-based 1D phononic crystals (PnCs) with topologically distinct complete phononic bandgaps (PnBGs) and the observation of a topologically protected state of elastic waves at their interface. By choosing different structural parameters of unit cells, two PnCs can possess a common PnBG with different topological nature. At the interface between the two PnCs, a topological interface mode with a quality factor of ~5,650 is observed in the PnBG. Spatial confinement of the interface mode is also confirmed by using photoelastic imaging technique. Such topologically protected elastic states are potentially applicable for constructing novel phononic devices. 2 Topological phenomena in quantum Hall, quantum spin Hall systems and topological insulators have been extensively studied in condensed matter physics 1,2 . A hallmark of such phenomena is topologically protected edge states which are robust against defects and imperfection. The presence of the topological edge states is due to topological characters of bulk electronic bands, which is called the bulk-edge correspondence 3,4 . Recently, topological concepts have also been extended to bosonic systems including photonic and phononic structures which support the topologically protected states of light [5][6][7][8][9][10][11][12][13][14][15][16] , acoustic 17-24 and mechanical [25][26][27][28][29][30] waves for various applications. Most of experimental studies in mechanical systems have focused on discrete structures such as coupled pendula 27,28 or granular chains 30 .Although they are useful for describing topological concepts in mechanical systems, continuous solid structures supporting topological elastic waves are highly expected to realize practical high speed phononic applications. In contrast to the intensive theoretical studies of the topological elastic waves [31][32][33][34] , there is a lack of an experimental demonstration in the continuous structures. One of the main challenges is due to high modal densities of elastic waves in continuous-solid structures, preventing the formation of complete PnBGs with topologically distinct properties. Very recently, experimental demonstration of topological elastic waves using continuous structures has been reported 35,36 . However, the structures have only partial phononic bandgap (PnBG) which can cause loss of the topological elastic states by coupling with other propagation modes. Thus, it remains a challenge to realize topological elastic waves in continuous structures with complete PnBGs.To the best of our knowledge, experimental demonstration of topological elastic waves in continuous structures with complete PnBGs is very limited even in one-dimensional (1D) periodic system due to their high modal densities.In this report, we report the experimental realization of topological interface state in solidstructured quasi 1D phononic crystals (PnCs) 37 . In 1D periodic systems, topologically protected edge states are zero-dimensional (0D), localized at the interface between two PnCs...

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“…We first uncover the spinorial characteristics of elastic waves in crystals composed of connected masses and springs. An externally applied spatio-temporal modulation of the spring striffness can also be employed to break the symmetry of the system further [30]. The modulation is shown to be able to tune the spinor part of the elastic wave function and therefore its topology.…”

Section: Intrinsic Topological Phononic Structuresmentioning

confidence: 99%

One-Dimensional Mass-Spring Chains Supporting Elastic Waves with Non-Conventional Topology

Deymier

Runge

2016

Crystals

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There are two classes of phononic structures that can support elastic waves with non-conventional topology, namely intrinsic and extrinsic systems. The non-conventional topology of elastic wave results from breaking time reversal symmetry (T-symmetry) of wave propagation. In extrinsic systems, energy is injected into the phononic structure to break T-symmetry. In intrinsic systems symmetry is broken through the medium microstructure that may lead to internal resonances. Mass-spring composite structures are introduced as metaphors for more complex phononic crystals with non-conventional topology. The elastic wave equation of motion of an intrinsic phononic structure composed of two coupled one-dimensional (1D) harmonic chains can be factored into a Dirac-like equation, leading to antisymmetric modes that have spinor character and therefore non-conventional topology in wave number space. The topology of the elastic waves can be further modified by subjecting phononic structures to externally-induced spatio-temporal modulation of their elastic properties. Such modulations can be actuated through photo-elastic effects, magneto-elastic effects, piezo-electric effects or external mechanical effects. We also uncover an analogy between a combined intrinsic-extrinsic systems composed of a simple one-dimensional harmonic chain coupled to a rigid substrate subjected to a spatio-temporal modulation of the side spring stiffness and the Dirac equation in the presence of an electromagnetic field. The modulation is shown to be able to tune the spinor part of the elastic wave function and therefore its topology. This analogy between classical mechanics and quantum phenomena offers new modalities for developing more complex functions of phononic crystals and acoustic metamaterials.

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Bulk elastic waves with unidirectional backscattering-immune topological states in a time-dependent superlattice

Cited by 128 publications

References 24 publications

Nonreciprocal Thermal Material by Spatiotemporal Modulation

Nonreciprocal Thermal Material by Spatiotemporal Modulation

Topologically protected elastic waves in one-dimensional phononic crystals of continuous media

One-Dimensional Mass-Spring Chains Supporting Elastic Waves with Non-Conventional Topology

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