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Carbon has various allotropes showing rich physical properties. Here, we take net C and net W as the research objects. They are all composed of carbonic squares C4, hexagons C6, and octagons C8, but with different compositions. Using the combination of density functional theory calculations and non-equilibrium Green’s function method, we study the significant changes in electronic structures and transport behaviors in response to external strain. For net C, tunable negative differential resistance (NDR) is observed. The NDR bias region can be moved and widened, while its peak-to-valley ratio can be increased from the original 1.14 to largest 2.67. The electrical conductivity of net W exhibits a very good linear relationship within a large strain range from −4% to +4%, and it can be increased to 219.9%. By analyzing their band structures, the effective regulations of strain on both the NDR and linear conductivity are explained. These results show not only the differences from deformation for various carbon rings under strain but also a certain guiding significance for applications in electronic devices.

The acoustic analogy of topological insulators is a hot field of materials research. On one-dimensional acoustic systems, many researchers have lately paid their attention to the applications of the Su-Schrieffer-Heeger (SSH) model, which can support topologically nontrivial phases. In this paper, we design a supercell composed of two identical hollow cylinders with a side split immersed in the air background. The supercell is arranged in a line to form a SSH model, which has three bandgaps including two zone-folding-induced gaps and a local resonant gap in the subwavelength region. By analyzing the eigenstates and calculating the Zak phases, we find that a topological phase transition takes place only in the zone-folding-induced gaps when we rotate the split-cylinders. Thus, a finite-size array, made of two sublattices with distinct topological properties, inevitably produces topological interface states on their interface. In addition, we demonstrate that the topological interface states can be adjusted in a wide frequency range by rotating the cylinders that control the coupling strength between two split-cylinders in one supercell. These tunable topological interface states may have potential application prospects in wave filtering, wave detecting, and so on.

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