By using first principles calculations, we theoretically investigate the electronic structures and the interfacial and optical properties of the two-dimensional tellurene (Te)–gallium arsenide (GaAs) van der Waals heterostructures (vdWHs), i.e., α-Te/GaAs and γ-Te/GaAs, formed using Te and GaAs monolayers. It has been demonstrated that, the semiconductor–semiconductor contacted α-Te/GaAs vdWH exhibits a type-II band alignment with a direct band gap of 0.28 eV while the metal–semiconductor contacted γ-Te/GaAs vdWH has a p-type Schottky contact with a Schottky barrier height (SBH) of 0.36 eV at the interface. The transition from type-II to type-III band alignment is observed firstly in the α-Te/GaAs vdWH when the in-plane biaxial strain is less than −5.2% and larger than 4.4%, meanwhile, the p-type Schottky contact to Ohmic contact transition may be realized in the γ-Te/GaAs vdWH when the in-plane biaxial strain is less than −2.4%. Finally, the maximum optical absorption coefficients of the α- and γ-Te/GaAs vdWHs have been found to be up to 31% and 29%, respectively, and may be modulated effectively by applying in-plane biaxial strain. The obtained results may be of importance in the design of nanoelectronic devices based on the proposed tellurene/GaAs vdWHs.

The thermal transport properties of NiNb₂O₆ as anode material for lithium-ion battery and the effect of strain were studied by machine learning interatomic potential combined with Boltzmann transport equation. The results show that the lattice thermal conductivity of NiNb₂O₆ along the three crystal directions [100], [010], and [001] are 0.947 W⋅m⁻¹⋅K⁻¹, 0.727 W⋅m⁻¹⋅K⁻¹, and 0.465 W⋅m⁻¹⋅K⁻¹, respectively, indicating the anisotropy of the lattice thermal conductivity of NiNb₂O₆. This anisotropy of the lattice thermal conductivity stems from the significant difference of phonon group velocities in different crystal directions of NiNb₂O₆. When the tensile strain is applied along the [001] crystal direction, the lattice thermal conductivity in all three directions decreases. However, when the compressive strain is applied, the lattice thermal conductivity in the [100] and [010] crystal directions is increased, while the lattice thermal conductivity in the [001] crystal direction is abnormally reduced due to the significant inhibition of compressive strain on the group velocity. These indicate that the anisotropy of thermal conductivity of NiNb₂O₆ can be enhanced by the compressive strain, and reduced by the tensile strain.

In this paper, an improved channel estimation scheme based on time-domain orthogonal gray complementary training sequence (Golay TS) is proposed to resist subcarrier mutual beat interference in 16-quadrature amplitude modulation multiband orthogonal-frequency-division-multiplexing ultrawide band over fiber (16QAM MB-OFDM UWBoF) systems. The simulation results showed that the performance of system with the improved Golay TS channel estimation scheme was improved by about 1dB compared with the traditional Golay TS channel estimation scheme, at a bit error rate (BER) of 3.8×10⁻³ after 70km standard single mode fiber (SSMF) transmission. At the same time, the synchronization and channel estimation performance of Golay TS and the selected frequency-domain orthogonal training sequences (TSs) were compared. The simulation results showed that the performance of system with the TSs channel estimation was improved by about 2.7dB compared with the improved Golay TS channel estimation.

A scheme that combines 256/128/64 quadrantal amplitude modulation (QAM) adaptive modulation with constant amplitude zero autocorrelation sequence (CAZAC) precoding in a multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband over fiber (UWBoF) system is proposed in this paper. CAZAC precoding enables a relatively balanced signal-to-noise ratio (SNR) within each band, and the use of adaptive modulation optimizes the upper limit of transmission performance in each subband. Simulation results show that CAZAC precoding combined with 256/128/64QAM and conventional 64QAM reduces the peak-to-average power ratio (PAPR) by 1 dB and 0.5 dB, respectively. The proposed scheme achieves PAPR performance comparable to conventional 64QAM. It confirms that CAZAC precoding performs better in the reduction of PAPR and bit error rate (BER) when combined with the 256/128/64QAM scheme.