Observations of Tamm modes in acoustic topological insulators

Liao, Danwei; Yue, Zichong; Zhang, Zhiwang; Wang, Hai-Xiao; Cheng, Ying; Liu, Xiaojun

doi:10.1063/5.0093995

Cited by 5 publications

(2 citation statements)

References 40 publications

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“…There might be a relative phase shift happening between the two branches of benzene when electrons propagate from left to right electrodes through it [34]. The combination of electronic wave functions along various pathways can lead to either constructive or destructive interference, resulting in changes to the transmission probability [35]. Figure 1a shows the benzene single molecule chemical structure junction attached to gold electrodes through pyridine anchors.…”

Section: Resultsmentioning

confidence: 99%

Quantum interference comparison between benzene, naphthalene, and azulene single molecular junction

Baker,

Al-Jobory

2024

Preprint

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The ability to build devices from single-molecular junctions depends on the fabrication of molecular structures. Here we report significant changes in the transmission coefficient for different connectivities for polycyclic aromatichydrocarbons (PAHs). In this study, we are using density functional theory DFT compared with the single orbital tight binding TB to investigate the transmission coefficient for three different molecules which are benzene, naphthalene and azulene with different point connections with electrodes. In the case of benzene the para connection, are leads to constructive quantum interference CQI, and the meta link is distractive quantum interference DQI. Next naphthalene and azulene have the same number of atoms, with five different connections, the result shows the even-even or odd-odd connection are DQI while the even-odd is CQI. This result is supported by the wave function molecular orbital plot. Finally, the TB calculations are in good agreement with DFT.

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Section: Resultsmentioning

confidence: 99%

Quantum interference comparison between benzene, naphthalene, and azulene single molecular junction

Baker,

Al-Jobory

2024

Preprint

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“…In 1D periodic systems, the topology of the bands is characterized by the concept of Zak phase, a special kind of Berry phase [24][25][26][27][28]. Recently, topological interface states and Zak phase have been extended to various branches of physics such as photonics [26,[29][30][31][32][33][34], plasmonics [22,35], acoustics and mechanical systems [36][37][38][39] and metamaterials [40,41]. The topological invariant has been successfully applied to predict the existence of interface states from the Zak phases of bulk bands.…”

Section: Introductionmentioning

confidence: 99%

Tunable Topological Acoustic Tamm States in Comblike Structures Based on Band Inversion around Flat Bands

et al. 2022

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We investigate the existence of acoustic Tamm states at the interface between two one-dimensional (1D) comblike phononic crystals (PnCs) based on slender tubes and discuss their topological or trivial character. The PnCs consist of stubs grafted periodically along a waveguide and the two crystals differ by their geometrical parameters (period and length of the stubs). We use several approaches to discuss the existence of Tamm states and their topology when connecting two half-crystals. First, we derive a necessary and sufficient condition on the existence of interface states based on the analysis of the bulk band structure and the symmetry of the band edge states. This approach is equivalent to an analysis of the Zak phases of the bulk bands in the two crystals. Indeed, a topological interface state should necessarily exist in any common bandgap of the two PnCs for which the lower (upper) band edges have opposite symmetries. A novelty of our structure consists in the fact that the symmetry inversion results from a band closure (flat band) rather than from a gap closure, in contrast to previous works. Then, such interface states are revealed through different physical quantities, namely: (i) the local density of states (LDOS), which exhibits a high localization around the interface; (ii) sharp peaks in the transmission spectra in the common bandgap when two finite crystals are connected together; (iii) the phases of the reflection coefficients at the boundary of each PnC with a waveguide, which have a direct relationship with the Zak phases. In addition, we show that the interface states can transform to bound states in the continuum (BICs). These BICs are induced by the cavity separating both PnCs and they remain robust to any geometrical disorder induced by the stubs and segments around this cavity. Finally, we show the impossibility of interface states between two connected PnCs with different stub lengths and similar periods. The sensitivity of these states to interface perturbations can find many practical applications in PnC sensors.

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Acoustic real second-order nodal-loop semimetal and non-Hermitian modulation

Yue,

Zhang,

Cheng

et al. 2023

Applied Physics Letters

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The unique features of spinless time-reversal symmetry and tunable ℤ2 gauge fields in artificial systems facilitate the emergence of topological properties in the landscape, such as the recently explored Möbius-twisted phase and real second-order nodal-loop semimetals. However, these properties have predominantly been proposed only in theoretical frameworks. In this study, we present a cunningly designed blueprint for realizing an acoustic real second-order nodal-loop semimetal through the incorporation of projective translation symmetry into a three-dimensional stacked acoustic graphitic lattice. Additionally, we introduce non-Hermitian modulation to the topologically protected propagation of degenerate drumhead surface and hinge states, which depend on the specific on-site gain and loss textures. It should be emphasized that this demonstration can be extended to other classical wave systems, thereby potentially opening up opportunities for the design of functional topological devices.

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Observations of Tamm modes in acoustic topological insulators

Cited by 5 publications

References 40 publications

Quantum interference comparison between benzene, naphthalene, and azulene single molecular junction

Quantum interference comparison between benzene, naphthalene, and azulene single molecular junction

Tunable Topological Acoustic Tamm States in Comblike Structures Based on Band Inversion around Flat Bands

Acoustic real second-order nodal-loop semimetal and non-Hermitian modulation

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