Two-dimensional tetragonal ZnB: A nodalline semimetal with good transport propertiesZhao, Yong-Chun; Zhu, Ming-Xin; Li, Sheng-Shi; Li, Ping
doi: 10.1088/1674-1056/ac8f33pmid: N/A
Nodal-line semimetals have become a research hot-spot due to their novel properties and great potential application in spin electronics. It is more challenging to find 2D nodal-line semimetals that can resist the spin–orbit coupling (SOC) effect. Here, we predict that 2D tetragonal ZnB is a nodal-line semimetal with great transport properties. There are two crossing bands centered on the S point at the Fermi surface without SOC, which are mainly composed of the pxyorbitals of Zn and B atoms and the pzorbitals of the B atom. Therefore, the system presents a nodal line centered on the S point in its Brillouin zone (BZ). And the nodal line is protected by the horizontal mirror symmetry Mz. We further examine the robustness of a nodal line under biaxial strain by applying up to −4% in-plane compressive strain and 5% tensile strain on the ZnB monolayer, respectively. The transmission along the a direction is significantly stronger than that along the b direction in the conductive channel. The current in the a direction is as high as 26.63 μA at 0.8 V, and that in the b direction reaches 8.68 μA at 0.8 V. It is interesting that the transport characteristics of ZnB show the negative differential resistance (NDR) effect after 0.8 V along the a (b) direction. The results provide an ideal platform for research of fundamental physics of 2D nodal-line fermions and nanoscale spintronics, as well as the design of new quantum devices.
Oxidation behavior of Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2C-Mx C (M = Ti, Zr, Hf, Nb, Ta) composite ceramic at high temperatureXu, Shuai; Wang, Tao; Wang, Xingang; Wu, Lu; Fang, Zhongqiang; Ge, Fangfang; Meng, Xuan; Liao, Qing; Wei, Jinchun; Li, Bingsheng
doi: 10.1088/1674-1056/ac9a38pmid: N/A
Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2C–MxC composite ceramic was prepared by hot press sintering, with the Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2C high-entropy carbide as the main phase. Secondary phase MxC (M = Ti, Zr, Hf, Nb, Ta) was found to be distributed relatively uniform in the composite ceramic. The oxidation behavior of the ceramic was examined after exposure to 923 K and 1173 K. Morphology of the surface and cross sections of all oxidation samples were observed. The characteristics of the oxidation behavior of the high-entropy carbide and the secondary phase MxC were compared and analyzed. The secondary phases (such as Ti-rich carbide or Hf-rich carbide) in the material were seriously oxidized at 923 K and 1173 K, which reflects the superior oxidation performance of the high-entropy carbide. The nano high-entropy oxides with Ti, Zr, Hf, Nb, Ta, and O elements were discovered by oxidation of the composite ceramic. This research will help deepen the understanding of the oxidation mechanism of high-entropy carbide and composite ceramic.
Magnetic ordering induced magnetodielectric effect in Ho2Cu2O5 and Yb2Cu2O5Jin, Hao; Huang, Shuai; Wan, Kai-Qi; Zhu, Chang-Ming; Wang, Hai-Ou; Su, Kun-Peng; Huo, De-Xuan
doi: 10.1088/1674-1056/ac904apmid: N/A
Materials with strongly coupled magnetic and electronic degrees of freedom provide new possibilities for practical applications. In this paper, we have investigated the structure, magnetic property, and magnetodielectric (MD) effect in Ho2Cu2O5 and Yb2Cu2O5 polycrystalline samples, which possess a non-centrosymmetric polar structure with space group Pna21. In Ho2Cu2O5, Ho3+ and Cu2+ sublattices order simultaneously, exhibiting a typical paramagnetic to antiferromagnetic transition at 13.1 K. While for Yb2Cu2O5, two magnetic transitions which originate from the orderings of Yb3+ (7.8 K) and Cu2+ (13.5 K) sublattices are observed. A magnetic field induced metamagnetic transition is obtained in these two cuprates below Néel temperature (TN). By means of dielectric measurement, distinct MD effect is demonstrated by the dielectric anomaly at TN. Meanwhile, the MD effect is found to be directly related to the metamagnetic transition. Due to the specific spin configuration and different spin evolution in the magnetic field, a positive MD effect is formed in Ho2Cu2O5, and a negative one is observed in Yb2Cu2O5. The spontaneous dielectric anomaly at TN is regarded as arising from the shifts in optical phonon frequencies, and the magnetoelectric coupling is used to interpret the magnetic field induced MD effect. Moreover, an H–T phase diagram is constructed for Ho2Cu2O5 and Yb2Cu2O5 based on the results of isothermal magnetic and dielectric hysteresis loops.
Generation of quasi-chirp-free isolated attosecond pulses from atoms under the action of orthogonal two-color combined pulse of fundamental frequency and higher intensity second harmonic fieldsYu, Rui-Xian; Qiao, Yue; Li, Ping; Wang, Jun; Chen, Ji-Gen; Feng, Wei; Guo, Fu-Ming; Yang, Yu-Jun
doi: 10.1088/1674-1056/acc80apmid: N/A
The intrinsic chirp of high-order harmonic generation is an important factor limiting the production of ultrashort attosecond pulses. Based on numerically solving the time-dependent Schrödinger equation, the generation process of high-order harmonic from the He atom under the action of orthogonal two-color combined pulse of fundamental frequency and higher intensity second harmonic fields is studied. In this paper, we propose to achieve quasi-chirp-free isolated attosecond pulses by superimposing a higher second-harmonic field on the orthogonal direction of the fundamental frequency field. It is found that the high-energy part of its harmonic emission exhibits small chirp characteristics, which can be used to synthesize isolated attosecond pulses. Through the analysis of the wave packets evolution and the classical motion trajectories of the electron, it is demonstrated that the quasi-chirp-free harmonic can be attributed to the simultaneous return of electrons ionized at different times to the parent particle. The influence of the relative phase of the two pulses on the harmonics is further analyzed, and it is observed that this phenomenon is sensitive to the relative phase, but it can still generate isolated attosecond pulses within a certain phase.
High harmonic generation in crystal SiO2 by sub-10-fs laser pulsesWang, Shuai; Guo, Jiawei; He, Xinkui; Liang, Yueying; Xie, Baichuan; Zhong, Shiyang; Teng, Hao; Wei, Zhiyi
doi: 10.1088/1674-1056/acc452pmid: N/A
The high harmonic generation (HHG) by few-cycle laser pulses is essential for research in strong-field solid-state physics. Through comparison of high harmonic spectra of solids generated by laser pulses with varying durations, we discovered that lasers with good dispersion compensation are capable of producing a broad spectrum of high harmonics. As the pulse duration is further compressed, several interference peaks appear in the broad spectrum. Moreover, we conducted simulations using the semiconductor Bloch equation, considering the effect of Berry curvature, to better understand this process. Our work provides a valuable approach for studying HHG by few-cycle laser pulses in solid materials, expanding the application of HHG in attosecond physics.
Influence of acceleration on relativistic nonlinear Thomson scattering in tightly focused linearly polarized laser pulsesChang, Yifan; Wang, Yubo; Wang, Chang; Shen, Yuting; Tian, Youwei
doi: 10.1088/1674-1056/ac89e6pmid: N/A
The influence of acceleration of electrons on relativistic nonlinear Thomson scattering in tightly focused linearly polarized laser pulses is investigated for the first time. In the framework of classical electrodynamics, it is deduced and found that the more severe the change in the electron transverse acceleration, the stronger the asymmetry of the radiation angle distribution, and the greater the transverse acceleration, the greater the radiation energy. Tightly focused, ultrashort, and high-intensity lasers lead to violent electron acceleration processes, resulting in a bifurcated radiation structure with asymmetry and higher energy. Additionally, a change in the initial phase of the laser brings about periodic change of the acceleration, which in turn makes the radiation change periodically with the initial phase. In other cases, the radiation is in a symmetrical double-peak structure. These phenomena will help us to modulate radiation with more energy collimation.
Single-event-transient effect in nanotube tunnel field-effect transistor with bias-induced electron–hole bilayerWang, Xue-Ke; Sun, Ya-Bin; Liu, Zi-Yu; Liu, Yun; Li, Xiao-Jin; Shi, Yan-Ling
doi: 10.1088/1674-1056/ac9180pmid: N/A
The single event transient (SET) effect in nanotube tunneling field-effect transistor with bias-induced electron–hole bilayer (EHBNT-TFET) is investigated by 3-D TCAD simulation for the first time. The effects of linear energy transfer (LET), characteristic radius, strike angle, electrode bias and hit location on SET response are evaluated in detail. The simulation results show that the peak value of transient drain current is up to 0.08 mA for heavy ion irradiation with characteristic radius of 50 nm and LET of 10 MeV⋅cm2/mg, which is much higher than the on-state current of EHBNT-TFET. The SET response of EHBNT-TFET presents an obvious dependence on LET, strike angle, drain bias and hit location. As LET increases from 2 MeV⋅cm2/mg to 10 MeV⋅cm2/mg, the peak drain current increases monotonically from 0.015 mA to 0.08 mA. The strike angle has an greater impact on peak drain current especially for the smaller characteristic radius. The peak drain current and collected charge increase by 0.014 mA and 0.06 fC, respectively, as the drain bias increases from 0.1 V to 0.9 V. Whether from the horizontal or the vertical direction, the most sensitive hit location is related to wt. The underlying physical mechanism is explored and discussed.