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    SPECIAL TOPIC — Celebrating the 70th Anniversary of the Physics of Jilin University

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    Near-infrared photocatalysis based on upconversion nanomaterials
    Xingyuan Guo(郭星原), Zhe Wang(王哲), Shengyan Yin(尹升燕), and Weiping Qin(秦伟平)
    Chin. Phys. B, 2022, 31 (10): 108201.   DOI: 10.1088/1674-1056/ac7556
    Abstract97)   HTML2)    PDF (845KB)(32)      
    As the global energy crisis and environmental pollution problems become increasingly severe, it is important to develop new energy capture and pollution management methods. Among these new technologies, photocatalysis has garnered significant interest because of its significant application prospects in harnessing pollution-free solar energy to degrade organic pollutants. From a fundamental scientific and technical perspective, improved optical frequency is a key research topic that provides a useful framework for studying the optical processes impacted by the local photonic environment. This type of study is especially pertinent because plasmonics emphasizes nonlinearity. Thus, near-infrared (NIR) catalysis has received considerable attention. In this review, we aimed to provide an integrated framework for NIR photocatalysis. We briefly introduce photocatalysis based on upconversion (UC) materials, including the efficiency of UC materials and the bination and energy transfer process between the semiconductor and UC particles as well as photoelectric response photocontrolled-delivery and photodynamic therapy based on NIR-responsive materials.
    Dynamic stabilization of atomic ionization in a high-frequency laser field with different initial angular momenta
    Di-Yu Zhang(张頔玉), Yue Qiao(乔月), Wen-Di Lan(蓝文迪), Jun Wang(王俊), Fu-Ming Guo(郭福明), Yu-Jun Yang(杨玉军), and Da-Jun Ding(丁大军)
    Chin. Phys. B, 2022, 31 (10): 103202.   DOI: 10.1088/1674-1056/ac892a
    Abstract117)   HTML4)    PDF (3298KB)(44)      
    We investigated the ionization of an atom with different orbital angular momenta in a high-frequency laser field by solving the time-dependent Schrödinger equation. The results showed that the ionization stabilization features changed with the relative direction between the angular momentum of the initial state and the vector field of the laser pulse. The ionization mechanism of the atom irradiated by a high frequency was explained by calculating the transition matrix and evolution of the time-dependent wave packet. This study can provide comprehensive understanding to improve atomic nonadiabatic ionization.
    Amplitude and rotation of the ellipticity of harmonicsfrom a linearly polarized laser field
    Ping Li(李萍), Na Gao(高娜), Rui-Xian Yu(蔚瑞贤), Jun Wang(王俊), Su-Yu Li(李苏宇), Fu-Ming Guo(郭福明), and Yu-Jun Yang(杨玉军)
    Chin. Phys. B, 2022, 31 (10): 103303.   DOI: 10.1088/1674-1056/ac8ce8
    Abstract143)   HTML0)    PDF (5152KB)(53)      
    We simulate the dynamic response of H2+ in a linearly polarized laser field by numerically solving the time-dependent Schrödinger equation. The elliptically polarized high-order harmonics generated by H2+ irradiated by the linearly polarized laser field are systematically investigated. The result shows that the amplitude and rotation of the ellipticity of harmonics are affected by the alignment angle and internuclear distance of the molecule. Analyzing the change in forces acted on the ionized electrons and the trajectories of the electrons, the phenomena are found to be due to the change in the direction of the total Coulomb forces from the two nuclei felt by the recollided ionized electrons in the direction perpendicular to the laser polarization direction. Based on the influence law, we can select the harmonics with a specific frequency band under different alignment angles and then synthesize the isolated attosecond pulses with different rotations, which can be continuously converted from right-handed circular polarization, linear polarization, and left-handed circular polarization by changing the alignment angle. This study provides a new possible approach to the real-time detection of molecular states by using attosecond pulses and obtaining more optimized harmonics with molecular properties.
    Femtosecond laser-induced Cu plasma spectra at different laser polarizations and sample temperatures
    Yitong Liu(刘奕彤), Qiuyun Wang(王秋云), Luyun Jiang(蒋陆昀), Anmin Chen(陈安民), Jianhui Han(韩建慧), and Mingxing Jin(金明星)
    Chin. Phys. B, 2022, 31 (10): 105201.   DOI: 10.1088/1674-1056/ac6864
    Abstract103)   HTML3)    PDF (813KB)(36)      
    Laser-induced breakdown spectroscopy (LIBS) is a good technique for detecting and analyzing material elements due to the plasma emission produced by the high-power laser pulse. Currently, a significant topic of LIBS research is improving the emission intensity of LIBS. This study investigated the effect of laser-polarization on femtosecond laser-ablated Cu plasma spectra at different sample temperatures. The measured lines under circularly polarized lasers were higher than those under linearly and elliptically polarized lasers. The enhancement effect was evident at higher Cu temperatures when comparing the plasma spectra that have circular and linear polarizations for different target temperatures. To understand the influence of laser-polarization and sample temperature on signal intensity, we calculated the plasma temperature (PT) and electron density (ED) . The change in PT and ED was consistent with the change in the atomic lines as the laser polarization was being adjusted. When raising the Cu temperature, the PT increased while the ED decreased. Raising the Cu temperature whilst adjusting the laser-polarization is effective for improving the signal of femtosecond LIBS compared to raising the initial sample temperature alone or only changing the laser polarization.
    Pressure-induced phase transition in transition metal trifluorides
    Peng Liu(刘鹏), Meiling Xu(徐美玲), Jian Lv(吕健), Pengyue Gao(高朋越), Chengxi Huang(黄呈熙), Yinwei Li(李印威), Jianyun Wang(王建云), Yanchao Wang(王彦超), and Mi Zhou(周密)
    Chin. Phys. B, 2022, 31 (10): 106104.   DOI: 10.1088/1674-1056/ac5887
    Abstract116)   HTML1)    PDF (804KB)(36)      
    As a fundamental thermodynamic variable, pressure can alter the bonding patterns and drive phase transitions leading to the creation of new high-pressure phases with exotic properties that are inaccessible at ambient pressure. Using the swarm intelligence structural prediction method, the phase transition of TiF3, from R—3c to the Pnma phase, was predicted at high pressure, accompanied by the destruction of TiF6 octahedra and formation of TiF8 square antiprismatic units. The Pnma phase of TiF3, formed using the laser-heated diamond-anvil-cell technique was confirmed via high-pressure x-ray diffraction experiments. Furthermore, the in situ electrical measurements indicate that the newly found Pnma phase has a semiconducting character, which is also consistent with the electronic band structure calculations. Finally, it was shown that this pressure-induced phase transition is a general phenomenon in ScF3, VF3, CrF3, and MnF3, offering valuable insights into the high-pressure phases of transition metal trifluorides.
    Synthesis and superconductivity in yttrium superhydrides under high pressure
    Yingying Wang(王莹莹), Kui Wang(王奎), Yao Sun(孙尧), Liang Ma(马良), Yanchao Wang(王彦超), Bo Zou(邹勃), Guangtao Liu(刘广韬), Mi Zhou(周密), and Hongbo Wang(王洪波)
    Chin. Phys. B, 2022, 31 (10): 106201.   DOI: 10.1088/1674-1056/ac872e
    Abstract119)   HTML0)    PDF (1060KB)(22)      
    Flourishing rare earth superhydrides are a class of recently discovered materials that exhibit near-room-temperature superconductivity at high pressures, ushering in a new era of superconductivity research at high pressures. Yttrium superhydrides drew the most attention among these superhydrides due to their abundance of stoichiometries and excellent superconductivities. Here, we carried out a comprehensive study of yttrium superhydrides in a wide pressure range of 140 GPa—300 GPa. We successfully synthesized a series of superhydrides with the compositions of YH4, YH6, YH7, and YH9, and reported superconducting transition temperatures of 82 K at 167 GPa, 218 K at 165 GPa, 29 K at 162 GPa, and 230 K at 300 GPa, respectively, as evidenced by sharp drops in resistance. The structure and superconductivity of YH4 were taken as a representative example and were also examined using x-ray diffraction measurements and the superconductivity suppression under external magnetic fields, respectively. Clathrate YH10, a candidate for room-temperature superconductor, was not synthesized within the study pressure and temperature ranges of up to 300 GPa and 2000 K. The current study established a detailed foundation for future research into room-temperature superconductors in polynary yttrium-based superhydrides.
    Effect of the codoping of N—H—O on the growth characteristics and defects of diamonds under high temperature and high pressure
    Zhenghao Cai(蔡正浩), Bowei Li(李博维), Liangchao Chen(陈良超), Zhiwen Wang(王志文), Shuai Fang(房帅), Yongkui Wang(王永奎), Hongan Ma(马红安), and Xiaopeng Jia(贾晓鹏)
    Chin. Phys. B, 2022, 31 (10): 108104.   DOI: 10.1088/1674-1056/ac7866
    Abstract129)   HTML0)    PDF (1196KB)(21)      
    Diamond crystals were synthesized with different doping proportions of N—H—O at 5.5 GPa—7.1 GPa and 1370 °C—1450 °C. With the increase in the N—H—O doping ratio, the crystal growth rate decreased, the temperature and pressure conditions required for diamond nucleation became increasingly stringent, and the diamond crystallization process was affected. [111] became the dominant plane of diamonds; surface morphology became block-like; and growth texture, stacking faults, and etch pits increased. The diamond crystals had a two-dimensional growth habit. Increasing the doping concentration also increased the amount of N that entered the diamond crystals as confirmed via Fourier transform infrared spectroscopy. However, crystal quality gradually deteriorated as verified by the red-shifting of Raman peak positions and the widening of the Raman full width at half maximum. With the increase in the doping ratio, the photoluminescence property of the diamond crystals also drastically changed. The intensity of the N vacancy center of the diamond crystals changed, and several Ni-related defect centers, such as the NE1 and NE3 centers, appeared. Diamond synthesis in N—H—O-bearing fluid provides important information for deepening our understanding of the growth characteristics of diamonds in complex systems and the formation mechanism of natural diamonds, which are almost always N-rich and full of various defect centers. Meanwhile, this study proved that the type of defect centers in diamond crystals could be regulated by controlling the N—H—O impurity contents of the synthesis system.
    Design of vertical diamond Schottky barrier diode with junction terminal extension structure by using the n-Ga2O3/p-diamond heterojunction
    Wang Lin(林旺), Ting-Ting Wang(王婷婷), Qi-Liang Wang(王启亮), Xian-Yi Lv(吕宪义), Gen-Zhuang Li(李根壮), Liu-An Li(李柳暗), Jin-Ping Ao(敖金平), and Guang-Tian Zou(邹广田)
    Chin. Phys. B, 2022, 31 (10): 108105.   DOI: 10.1088/1674-1056/ac7e37
    Abstract120)   HTML1)    PDF (1211KB)(23)      
    A novel junction terminal extension structure is proposed for vertical diamond Schottky barrier diodes (SBDs) by using an n-Ga2O3/p-diamond heterojunction. The depletion region of the heterojunction suppresses part of the forward current conduction path, which slightly increases the on-resistance. On the other hand, the reverse breakdown voltage is enhanced obviously because of attenuated electric field crowding. By optimizing the doping concentration, length, and depth of n-Ga2O3, the trade-off between on-resistance and breakdown voltage with a high Baliga figure of merit (FOM) value is realized through Silvaco technology computer-aided design simulation. In addition, the effect of the work functions of the Schottky electrodes is evaluated. The results are beneficial to realizing a high-performance vertical diamond SBD.
    Relationship between the spatial position of the seed and growth mode for single-crystal diamond grown with an enclosed-type holder
    Wen-Liang Xie(谢文良), Xian-Yi Lv(吕宪义), Qi-Liang Wang(王启亮), Liu-An Li(李柳暗), and Guang-Tian Zou(邹广田)
    Chin. Phys. B, 2022, 31 (10): 108106.   DOI: 10.1088/1674-1056/ac7e35
    Abstract142)   HTML0)    PDF (856KB)(35)      
    The relationship between the spatial position of the diamond seed and growth mode is investigated with an enclosed-type holder for single-crystal diamond growth using the microwave plasma chemical vapor deposition epitaxial method. The results demonstrate that there are three main regions by varying the spatial position of the seed. Due to the plasma concentration occurring at the seed edge, a larger depth is beneficial to transfer the plasma to the holder surface and suppress the polycrystalline diamond rim around the seed edge. However, the plasma density at the edge decreases drastically when the depth is too large, resulting in the growth of a vicinal grain plane and the reduction of surface area. By adopting an appropriate spatial location, the size of single-crystal diamond can be increased from 7 mm × 7 mm × 0.35 mm to 8.6 mm × 8.6 mm × 2.8 mm without the polycrystalline diamond rim.