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| 1 | Temperature-induced Lifshitz transition in topological insulator candidate HfTe_5显示文摘The ongoing discoveries and studies of novel topological quantum materials have become an emergent and important field of condensed matter physics.Recently,HfTe_5 ignited renewed interest as a candidate of a novel topological material.The single-layer HfTe_5 is predicted to be a two-dimensional large band gap topological insulator and can be stacked into a bulk that may host a temperature-driven topological phase transition.Historically,HfTe_5 attracted considerable interest for its anomalous transport properties characterized by a peculiar resistivity peak accompanied by a sign reversal carrier type.The origin of the transport anomaly remains under a hot debate.Here we report the first high-resolution laser-based angle-resolved photoemission measurements on the temperature-dependent electronic structure in HfTe_5.Our results indicated that a temperature-induced Lifshitz transition occurs in HfTe_5,which provides a natural understanding on the origin of the transport anomaly in HfTe_5.In addition,our observations suggest that HfTe_5 is a weak topological insulator that is located at the phase boundary between weak and strong topological insulators at very low temperature. | Yan Zhang Chenlu Wang Guodong Liu Aiji Liang Lingxiao Zhao Jianwei Huang Qiang Gao Bing Shen Jing Liu Cheng Hu Wenjuan Zhao Genfu Chen Xiaowen Jia Li Yu Lin Zhao Shaolong He Fengfeng Zhang Shenjin Zhang Feng Yang Zhimin Wang Qinjun Peng Zuyan Xu Chuangtian Chen Xingjiang Zhou | 2017 | Science Bulletin2017，62，13： | 4 |
| 2 | Design and optimization of DBR in 980 nm bottom-emitting VCSEL显示文摘According to the theory of DBR,with the P-type DBR as an example,the electrical characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width and doping density of graded region are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs,which consists of 30 pairs P-type DBR and 28 pairs N-type DBR,are then fabricated. In P-type DBR,the width of graded region is 0.02 μm and the uniformity doping concentration is 2.5×1018cm-3. Its reflectivity is 99.9%. In N-type DBR,the width of graded region is also 0.02 μm and the uniformity doping concen-tration is 2×1018cm-3. Its reflectivity is 99.3%. The I-V curve shows that the series resistance of the device is about 0.05 Ω. According to the theory of DBR,with the P-type DBR as an example,the electri-cal characteristics and optical reflection of the DBR are analyzed by studying the energy band structure with various graded region widths and doping densities. The width and doping density of graded re-gion are decided through a comparative study. The P-type DBR of 980 nm VCSELs is designed,with Al0.9Ga0.1As and Al0.1Ga0.9As selected as the high and low refractive index material for the DBR. The 980 nm bottom VCSELs,which consist of 30 pairs P-type DBR and 28 pairs N-type DBR,are then fabri-cated. In P-type DBR,the width of graded region is 0.02 μm and the uniformity doping concentration is 2.5×1018cm-3. Its reflectivity is 99.9%. In N-type DBR,the width of graded region is also 0.02 μm and the uniformity doping concentration is 2×1018cm-3. Its reflectivity is 99.3%. The I-V curve shows that the series resistance of the device is about 0.05 Ω. | LI Te NING YongQiang HAO ErJuan CUI JinJiang ZHANG Yan LIU GuangYu QIN Li LIU Yun WANG LiJun CUI DaFu XU ZuYan | 2009 | Science in China(Series F)2009，52，7： | 4 |
| 3 | Electronic structure of exfoliated millimeter-sized monolayer WSe2 on silicon wafer显示文摘The mono layer WSe2 is in teresting and important for future application in nanoelectronics,spintronics and valleytronics devices,because it has the largest spin splitting and Ion gest valley coherence time among all the known monolayer transition-metal dichalcogenides(TMDs).Toobtain the large-area monolayer TMDs'crystal is the first step to manu facture scalable and high-performance electronic devices.In this letter,we have successfully fabricated millimeter-sized mono layer WSe2 single crystals with very high quality,based on our improved mecha nicalexfoliation method.With such superior samples,using standard high resolution angle-resolved photoemission spectroscopy,we didcomprehe nsive electronic band structure measurements on our mono layer WSe2.The overall band features point it to be a 1.2 eV direct bandgap semico nductor.Its spin splitting of the valence band at K point is found as 460 meV,which is 30 meV less than the corresponding band splitting in its bulk counterpart.The effective hole masses of valence bands are determined as 2.344 me atГ,and 0.529 me as well as 0.532 meat K for the upper and lower branch of splitting ban ds,respectively.And screening effect from substrate is shown to substa ntially impact onthe electronic properties.Our results provide importa nt insights into band structure engineering in mono layer TMDs.Our mono layer WSe2 crystals may constitute a valuable device platform. | Wenjuan Zhao Yuan Huang Cheng Shen Cong Li Yongqing Cai Yu Xu Hongtao Rong Qiang Gao Yang Wang Lin Zhao Lihong Bao Qingyan Wang Guangyu Zhang Hongjun Gao Zuyan Xu Xingjiang Zhou Guodong Liu | 2019 | Nano Research2019，12，12： | 2 |
| 4 | Study of the Retracing Behavior of the Phase-Matching Angle in Second Harmonic Generation显示文摘The retracing behavior of the phase-matching angle(RBPA)in many nonlinear optical crystals for second harmonic generation(SHG)has been demonstrated by calculation.The generality of this phenomenon is successfully explained by a theoretical analysis based on classical optics.The wavelengths of the fundamental waves and phasematching angles for describing the RBPA of eight kinds of crystals are presented.Furthermore,we point out that RBPA exists generally in both uniaxial and biaxial crystals for both type Ⅰ and type Ⅱ SHG. | LIU Xiang DENG Daoqun WU Ling-an XU Zuyan CHEN Chuangtian WU Baichang | 1994 | Chinese Physics Letters1994，11，5： | 1 |
| 5 | Emergence of superconductivity from fully incoherent normal state in an iron-based superconductor (Ba_(0.6)K_(0.4))Fe_2As_2显示文摘In unconventional superconductors, it is generally believed that understanding the physical properties of the normal state is a pre-requisite for understanding the superconductivity mechanism. In conventional superconductors like niobium or lead, the normal state is a Fermi liquid with a well-defined Fermi surface and well-defined quasipartcles along the Fermi surface. Superconductivity is realized in this case by the Fermi surface instability in the superconducting state and the formation and condensation of the electron pairs(Cooper pairing). The high temperature cuprate superconductors, on the other hand, represent another extreme case that superconductivity can be realized in the underdoped region where there is neither well-defined Fermi surface due to the pseudogap formation nor quasiparticles near the antinodal regions in the normal state. Here we report a novel scenario that superconductivity is realized in a system with well-defined Fermi surface but without quasiparticles along the Fermi surface in the normal state.High resolution laser-based angle-resolved photoemission measurements have been performed on an optimally-doped iron-based superconductor(Ba_(0.6)K_(0.4))Fe_2As_2. We find that, while sharp superconducting coherence peaks emerge in the superconducting state on the hole-like Fermi surface sheets, no quasiparticle peak is present in the normal state. Its electronic behaviours deviate strongly from a Fermi liquid system. The superconducting gap of such a system exhibits an unusual temperature dependence that it is nearly a constant in the superconducting state and abruptly closes at Tc. These observations have provided a new platform to study unconventional superconductivity in a non-Fermi liquid system. | Jianwei Huang Lin Zhao Cong Li Qiang Gao Jing Liu Yong Hu Yu Xu Yongqing Cai Dingsong Wu Ying Ding Cheng Hu Huaxue Zhou Xiaoli Dong Guodong Liu Qingyan Wang Shenjin Zhang Zhimin Wang Fengfeng Zhang Feng Yang Qinjun Peng Zuyan Xu Chuangtian Chen Xingjiang Zhou | 2019 | Science Bulletin2019，64，1： | 1 |
| 6 | Efficient 266 nm ultraviolet beam generation in K2Al2B2O7 crystal显示文摘 | Lu Junhun Wang Gulling Xu Zuyan | 2002 | Chin Phys Lett2002，19，5： | 1 |
| 7 | NdxLa2-xCaB10O19 : Synthesis and Character- ization显示文摘 | Peizhen Fu Junxin Wang Haiquan Guo Hengli Zhang Zuyan Xu Fan Guo Yicheng Wu | 2000 | Progress in Crystal Growth and Characterization of Materi- als2000，，： | 1 |
| 8 | The effect of oxygen on the epitaxial growth of diamond显示文摘We studied the effect of oxygen on the growth quality of diamond epitaxial layers. After oxygen is added during the growth of the diamond epitaxial layer, as the thickness of the epitaxial layer increases, the full width at half maximum of the rocking curve of the(004) plane of diamond epitaxial layer increases continuously, and, in addition, the intensities of both the Raman peaks and the free exciton emission peaks of the diamond epitaxial layer decrease continuously. These experimental results demonstrate that as the thickness of the diamond epitaxial layer increases, the quality of the diamond epitaxial layer degrades. The strong etching effect of the OH radical groups in the plasma on the diamond epilayers leads to the degradation of their crystallinity. | Meng Gong Yanan Chen Wancheng Yu Peng Jin Zhanguo Wang Zhimin Wang Shenjin Zhang Feng Yang Fengfeng Zhang Qinjun Peng Zuyan Xu | 2018 | Journal of Semiconductors2018，39，12： | 1 |
| 9 | The Vacuum Ultraviolet Phase-matching Characteristics of Nonlinear Op- tical KBe2BO3F2 Crystal 显示文摘 | CHEN Chuangtian XU Zuyan DENG Daoqun | 1996 | Appl Phys Lett1996，68，21： | 1 |
| 10 | In situ carrier tuning in high temperature superconductor Bi2Sr2CaCu2O(8+δ)by potassium deposition显示文摘We report a successful tuning of the hole doping level over a wide range in high temperature superconductor Bi_2Sr_2CaCu_2O_(8+δ)(Bi2212) through successive in situ potassium(K) deposition. By taking high resolution angleresolved photoemission measurements on the Fermi surface and band structure of an overdoped Bi2212(T_c= 76 K) at different stages of K deposition, we found that the area of the hole-like Fermi surface around the Brillouin zone corner(p,p) shrinks with increasing K deposition. This indicates a continuous hole concentration change from initial 0.26 to eventual 0.09 after extensive K deposition, a net doping level change of 0.17 that makes it possible to bring Bi2212 from being originally overdoped, to optimally-doped, and eventually becoming heavily underdoped. The electronic behaviors with K deposition are consistent with those of Bi2212 samples with different hole doping levels. These results demonstrate that K deposition is an effective way of in situ controlling the hole concentration in Bi2212. This work opens a good way of studying the doping evolution of electronic structure and establishing the electronic phase diagram in Bi2212 that can be extended to other cuprate superconductors. | Yuxiao Zhang Cheng Hu Yong Hu Lin Zhao Ying Ding Xuan Sun Aiji Liang Yan Zhang Shaolong He Defa Liu Li Yu Guodong Liu Xiaoli Dong Genda Gu Chuangtian Chen Zuyan Xu Xingjiang Zhou | 2016 | Science Bulletin2016，61，13： | 1 |
| 11 | 4350<ce:hsp sp='0.25'/>W quasi-continuous-wave operation of a diode face-pumped ceramic Nd: YAG slab laser显示文摘 | Junchi Chen Jiang Li Jialin Xu Wenbin Liu Yong Bo Xiqi Feng Yiting Xu Dongliang Jiang Zhongzheng Chen Yubai Pan Yading Guo Biao Yan Chang Guo Lei Yuan Hongtao Yuan Yanyong Lin Yunsheng Xiao Qinjun Peng Wenqiang Lei Dafu Cui Zuyan Xu | 2014 | Optics and Laser Technology2014，，： | 1 |
| 12 | TUNABLE HIGH-POWER BaB_(2)O_(4) OPTICAL PARAMETRIC OSCILLATOR PUMPED AT 355nm显示文摘We report the operation of aβ-BaB_(2)O_(4)(BBO)optical parametric oscillator(OPO)broadly tunable in the visible and the near infrared.Quantum efficiency of 22.7%for the signal and 34.1%for the idler corresponding to the total energy conversion efficiency of 25.9%has been achieved.The maximum average output power and the maximum output energy reached 220m W and 22rnJ/pulse,respectively.By changing the matching angle of the OPO,the output wavelength was continuously scanned throughout 425-2144nm. | XU Zuyan DENG Daoqun WANG Yunping ZHENG Wanhua LIU Xiang WU Baichang CHEN Chuangtian | 1990 | Chinese Physics Letters1990，7，9： | 0 |
| 13 | High-Efficiency Second Harmonic Generation of a Pulsed Ti : Al_(2)O_(3) Laser with β-BaB_(2)O_(4) Crysta显示文摘Tunable blue radiation with a tuning range of 340-460nm has been generated using aβ-BaB_(2)O_(4) crystal for external frequency doubling of a ns-pulsed Ti:Al_(2)O_(3) laser.By pumping the Ti:sapphire with 94mJ/pulse of energy from the second harmonic of a Q-switched Nd:YAG laser,as much as 5.4mJ/pulse at 390nm with a bandwidth of 0.02nm was obtained.This represents an infrared to blue conversion efficiency of 36%and a total conversion(from 532nm to blue)of 5.7%. | LIU Xiang DENG Daoqun ZHANG Yufei XU Zuyan | 1994 | Chinese Physics Letters1994，11，9： | 0 |
| 14 | PICOSECOND NARROW-BAND SUPERLUMINESCENT OPTICAL PARAMETRIC SELF-AMPLIFICATION IN β-BaB_(2)O_(4) CRYSTAL PUMPED AT 354.7nm显示文摘A tunable picosecond narrow band β-BaB_(2)O_(4)(BBO)superluminescent optical parametric self-amplification(OPSA)pumped by the third harmonic of an actively-passively mode-locked Nd:YAG laser has been demonstrated.The output wavelength of the OPSA was tunable from 406.6nm to 2777nm.The maximum energy conversion efficiency was 11%.The maximum peak power of the visible output was as high as 13MW. | DENG Daoqun XU Zuyan WANG Yunping ZHENG Wanhua LIU Xiang WU Baichang CHEN Chuangtian | 1990 | Chinese Physics Letters1990，7，11： | 0 |
| 15 | Diode pumped Nd: YVO_4 laser at 671 nm with a type-Ⅱ noncritical phase-matched LBO显示文摘A diode pumped intracavity frequency-doubled Nd: YVO4 laser emitting at 671 nm with a type- Ⅱ noncritical phase-matched LBO crystal is reported. A maximum output power at 671 nm of 404 mW was obtained under an incident pump power of 5.16 W, with an optical-to-optical conversion efficiency up to 7.8%. The output power fluctuates less than 5% while the temperature change of the LBO crystal is maintained at ± 0.5℃ at the phase-matched temperature. | ZHANG Hengli , HOU Wei , WANG Jianming , XU Yao , XU Zuyan WU Baichang CHEN ChuangtianLaboratory of Optical Physics , Institute of Physics , Chinese Academy of Sciences , Beijing 100080, China Fujian Institute of Research on the Structure of Matter , Chinese Academy of Sciences , Fuzhou 350002, China | 1999 | Chinese Science Bulletin1999，44，15： | 0 |
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