Chin. Phys. B
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CN 11-5639/O4
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HighLights

Temperature-switching logic in MoS2 single transistors Hot!

Xiaozhang Chen(陈孝章), Lehua Gu(顾乐华), Lan Liu(刘岚), Huawei Chen(陈华威), Jingyu Li(栗敬俣), Chunsen Liu(刘春森), Peng Zhou(周鹏)
Chin. Phys. B, 2020, 29 (9): 097201 doi: 10.1088/1674-1056/aba9cf
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Due to their unique characteristics, two-dimensional (2D) materials have drawn great attention as promising candidates for the next generation of integrated circuits, which generate a calculation unit with a new working mechanism, called a logic transistor. To figure out the application prospects of logic transistors, exploring the temperature dependence of logic characteristics is important. In this work, we explore the temperature effect on the electrical characteristic of a logic transistor, finding that changes in temperature cause transformation in the calculation: logical output converts from ‘AND’ at 10 K to ‘OR’ at 250 K. The transformation phenomenon of temperature regulation in logical output is caused by energy band which decreases with increasing temperature. In the experiment, the indirect band gap of MoS2 shows an obvious decrease from 1.581 eV to 1.535 eV as the temperature increases from 10 K to 250 K. The change of threshold voltage with temperature is consistent with the energy band, which confirms the theoretical analysis. Therefore, as a promising material for future integrated circuits, the demonstrated characteristic of 2D transistors suggests possible application for future functional devices.

Intercalation of van der Waals layered materials: A route towards engineering of electron correlation Hot!

Jingjing Niu(牛晶晶), Wenjie Zhang(章文杰), Zhilin Li(李治林), Sixian Yang(杨嗣贤), Dayu Yan(闫大禹), Shulin Chen(陈树林), Zhepeng Zhang(张哲朋), Yanfeng Zhang(张艳锋), Xinguo Ren(任新国), Peng Gao(高鹏), Youguo Shi(石友国), Dapeng Yu(俞大鹏), Xiaosong Wu(吴孝松)
Chin. Phys. B, 2020, 29 (9): 097104 doi: 10.1088/1674-1056/abab85
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Being parent materials of two-dimensional (2D) crystals, van der Waals layered materials have received revived interest. In most 2D materials, the interaction between electrons is negligible. Introducing the interaction can give rise to a variety of exotic properties. Here, via intercalating a van der Waals layered compound VS2, we find evidence for electron correlation by extensive magnetic, thermal, electrical, and thermoelectric characterizations. The low temperature Sommerfeld coefficient is 64 mJ·K-2·mol-1 and the Kadowaki-Woods ratio rKW~0.20a0. Both supports an enhancement of the electron correlation. The temperature dependences of the resistivity and thermopower indicate an important role played by the Kondo effect. The Kondo temperature TK is estimated to be around 8 K. Our results suggest intercalation as a potential means to engineer the electron correlation in van der Waals materials, as well as 2D materials.

Epitaxial synthesis and electronic properties of monolayer Pd2Se3 Hot!

Peng Fan(范朋), Rui-Zi Zhang(张瑞梓), Jing Qi(戚竞), En Li(李恩), Guo-Jian Qian(钱国健), Hui Chen(陈辉), Dong-Fei Wang(王东飞), Qi Zheng(郑琦), Qin Wang(汪琴), Xiao Lin(林晓), Yu-Yang Zhang(张余洋), Shixuan Du(杜世萱), Hofer W A, Hong-Jun Gao(高鸿钧)
Chin. Phys. B, 2020, 29 (9): 098102 doi: 10.1088/1674-1056/abab80
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Two-dimensional (2D) materials received large amount of studies because of the enormous potential in basic science and industrial applications. Monolayer Pd2Se3 is a fascinating 2D material that was predicted to possess excellent thermoelectric, electronic, transport, and optical properties. However, the fabrication of large-scale and high-quality monolayer Pd2Se3 is still challenging. Here, we report the synthesis of large-scale and high-quality monolayer Pd2Se3 on graphene-SiC (0001) by a two-step epitaxial growth. The atomic structure of Pd2Se3 was investigated by scanning tunneling microscope (STM) and confirmed by non-contact atomic force microscope (nc-AFM). Two subgroups of Se atoms have been identified by nc-AFM image in agreement with the theoretically predicted atomic structure. Scanning tunneling spectroscopy (STS) reveals a bandgap of 1.2 eV, suggesting that monolayer Pd2Se3 can be a candidate for photoelectronic applications. The atomic structure and defect levels of a single Se vacancy were also investigated. The spatial distribution of STS near the Se vacancy reveals a highly anisotropic electronic behavior. The two-step epitaxial synthesis and characterization of Pd2Se3 provide a promising platform for future investigations and applications.

Some experimental schemes to identify quantum spin liquids Hot!

Yonghao Gao(高永豪), Gang Chen(陈钢)
Chin. Phys. B, 2020, 29 (9): 097501 doi: 10.1088/1674-1056/ab9df0
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Despite the apparent ubiquity and variety of quantum spin liquids in theory, experimental confirmation of spin liquids remains to be a huge challenge. Motivated by the recent surge of evidences for spin liquids in a series of candidate materials, we highlight the experimental schemes, involving the thermal Hall transport and spectrum measurements, that can result in smoking-gun signatures of spin liquids beyond the usual ones. For clarity, we investigate the square lattice spin liquids and theoretically predict the possible phenomena that may emerge in the corresponding spin liquids candidates. The mechanisms for these signatures can be traced back to either the intrinsic characters of spin liquids or the external field-driven behaviors. Our conclusion does not depend on the geometry of lattices and can broadly apply to other relevant spin liquids.

Dynamics and coherence resonance in a thermosensitive neuron driven by photocurrent Hot!

Ying Xu(徐莹), Minghua Liu(刘明华), Zhigang Zhu(朱志刚), Jun Ma(马军)
Chin. Phys. B, 2020, 29 (9): 098704 doi: 10.1088/1674-1056/ab9dee
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A feasible neuron model can be effective to estimate the mode transition in neural activities in a complex electromagnetic environment. When neurons are exposed to electromagnetic field, the continuous magnetization and polarization can generate nonlinear effect on the exchange and propagation of ions in the cell, and then the firing patterns can be regulated completely. The conductivity of ion channels can be affected by the temperature and the channel current is adjusted for regulating the excitability of neurons. In this paper, a phototube and a thermistor are used to the functions of neural circuit. The phototube is used to capture external illumination for energy injection, and a continuous signal source is obtained. The thermistor is used to percept the changes of temperature, and the channel current is changed to adjust the excitability of neuron. This functional neural circuit can encode the external heat (temperature) and illumination excitation, and the dynamics of neural activities is investigated in detail. The photocurrent generated in the phototube can be used as a signal source for the neural circuit, and the thermistor is used to estimate the conduction dependence on the temperature for neurons under heat effect. Bifurcation analysis and Hamilton energy are calculated to explore the mode selection. It is found that complete dynamical properties of biological neurons can be reproduced in spiking, bursting, and chaotic firing when the phototube is activated as voltage source. The functional neural circuit mainly presents spiking states when the photocurrent is handled as a stable current source. Gaussian white noise is imposed to detect the occurrence of coherence resonance. This neural circuit can provide possible guidance for investigating dynamics of neural networks and potential application in designing sensitive sensors.

Charge transfer in low-energy collisions ofBe3+ and B4+ ions with He Hot!

Kun Wang(王堃), Yi-Zhi Qu(屈一至), Chun-Hua Liu(刘春华), Ling Liu(刘玲), Yong Wu(吴勇), H P Liebermann, Robert J. Buenker
Chin. Phys. B, 2020, 29 (9): 093401 doi: 10.1088/1674-1056/aba276
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The nonradiative charge-transfer processes of Be3+(1s)/B4+(1s) colliding with He(1s2) are investigated by the quantum-mechanical molecular orbital close-coupling (QMOCC) method from 10 eV/u to 1800 eV/u. Total and state-selective cross sections are obtained and compared with other results available. Although the incident ions have the same number of electrons and collide with the same target, their cross sections are different due to the differences in molecular structure. For Be3+(1s) + He(1s2), only single-electron-capture (SEC) states are important and the total cross sections have a broad maximum around E=150 eV/u. While for B4+(1s) + He(1s2), both the SEC and double-electron-capture (DEC) processes are important, and the total SEC and DEC cross sections decrease rapidly with the energy decreasing.

Suppressing transition metal dissolution and deposition in lithium-ion batteries using oxide solid electrolyte coated polymer separator Hot!

Zhao Yan(闫昭), Hongyi Pan(潘弘毅), Junyang Wang(汪君洋), Rusong Chen(陈汝颂), Fei Luo(罗飞), Xiqian Yu(禹习谦), Hong Li(李泓)
Chin. Phys. B, 2020, 29 (8): 088201 doi: 10.1088/1674-1056/ab9610
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The dissolution of transition metal (TM) cations from oxide cathodes and the subsequent migration and deposition on the anode lead to the deconstruction of cathode materials and uncontrollable growth of solid electrode interphase (SEI). The above issues have been considered as main causes for the performance degradation of lithium-ion batteries (LIBs). In this work, we reported that the solid oxide electrolyte Li1.5Al0.5Ti1.5(PO4)3 (LATP) coating on polyethylene (PE) polymer separator can largely block the TM dissolution and deposition in LIBs. Scanning electron microscopy (SEM), second ion mass spectroscopy (SIMS), and Raman spectroscopy characterizations reveal that the granular surface of the LATP coating layer is converted to a dense morphology due to the reduction of LATP at discharge process. The as-formed dense surface layer can effectively hinder the TM deposition on the anode electrode and inhibit the TM dissolution from the cathode electrode. As a result, both the LiCoO2/SiO-graphite and LiMn2O4/SiO-graphite cells using LATP coated PE separator show substantially enhanced cycle performances compared with those cells with Al2O3 coated PE separator.

Quantization of electromagnetic modes and angular momentum on plasmonic nanowires Hot!

Guodong Zhu(朱国栋), Yangzhe Guo(郭杨喆), Bin Dong(董斌), Yurui Fang(方蔚瑞)
Chin. Phys. B, 2020, 29 (8): 087301 doi: 10.1088/1674-1056/ab9698
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Quantum theory of surface plasmons is very important for studying the interactions between light and different metal nanostructures in nanoplasmonics. In this work, using the canonical quantization method, the SPPs on nanowires and their orbital and spin angular momentums are investigated. The results show that the SPPs on nanowire carry both orbital and spin momentums during propagation. Later, the result is applied to the plasmonic nanowire waveguide to show the agreement of the theory. The study is helpful for the nano wire based plasmonic interactions and the quantum information based optical circuit in the future.

Growth and physical characterization of high resistivityFe: β-Ga2O3 crystals Hot!

Hao Zhang(张浩), Hui-Li Tang(唐慧丽), Nuo-Tian He(何诺天), Zhi-Chao Zhu(朱智超), Jia-Wen Chen(陈佳文), Bo Liu(刘波), Jun Xu(徐军)
Chin. Phys. B, 2020, 29 (8): 087201 doi: 10.1088/1674-1056/ab942d
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High quality 0.02 mol%, 0.05 mol%, and 0.08 mol% Fe:β-Ga2O3 single crystals were grown by the floating zone method. The crystal structure, optical, electrical, and thermal properties were measured and discussed. Fe:β-Ga2O3 single crystals showed transmittance of higher than 80% in the near infrared region. With the increase of the Fe doping concentration, the optical bandgaps reduced and room temperature resistivity increased. The resistivity of 0.08 mol% Fe:β-Ga2O3 crystal reached to 3.63×1011 Ω·cm. The high resistivity Fe:β-Ga2O3 single crystals could be applied as the substrate for the high-power field effect transistors (FETs).

Picosecond terahertz pump-probe realized from Chinese terahertz free-electron laser Hot!

Chao Wang(王超), Wen Xu(徐文), Hong-Ying Mei(梅红樱), Hua Qin(秦华), Xin-Nian Zhao(赵昕念), Hua Wen(温华), Chao Zhang(张超), Lan Ding(丁岚), Yong Xu(徐勇), Peng Li(李鹏), Dai Wu(吴岱), Ming Li(黎明)
Chin. Phys. B, 2020, 29 (8): 084101 doi: 10.1088/1674-1056/ab961b
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Electron energy relaxation time τ is one of the key physical parameters for electronic materials. In this study, we develop a new technique to measure τ in a semiconductor via monochrome picosecond (ps) terahertz (THz) pump and probe experiment. The special THz pulse structure of Chinese THz free-electron laser (CTFEL) is utilized to realize such a technique, which can be applied to the investigation into THz dynamics of electronic and optoelectronic materials and devices. We measure the THz dynamical electronic properties of high-mobility n-GaSb wafer at 1.2 THz, 1.6 THz, and 2.4 THz at room temperature and in free space. The obtained electron energy relaxation time for n-GaSb is in line with that measured via, e.g., four-wave mixing techniques. The major advantages of monochrome ps THz pump-probe in the study of electronic and optoelectronic materials are discussed in comparison with other ultrafast optoelectronic techniques. This work is relevant to the application of pulsed THz free-electron lasers and also to the development of advanced ultrafast measurement technique for the investigation of dynamical properties of electronic and optoelectronic materials.

Detection of HIV-1 antigen based on magnetic tunnel junction sensors Hot!

Li Li(李丽), Kai-Yu Mak(麦启宇), Yan Zhou(周艳)
Chin. Phys. B, 2020, 29 (8): 088701 doi: 10.1088/1674-1056/ab928d
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We report a p24 (HIV disease biomarker) detection assay using an MgO-based magnetic tunnel junction (MTJ) sensor and 20-nm magnetic nanoparticles. The MTJ array sensor with sensing area of 890×890 μ2 possessing a sensitivity of 1.39%/Oe was used to detect p24 antigens. It is demonstrated that the p24 antigens could be detected at a concentration of 0.01 μg/ml. The development of bio-detection systems based on magnetic tunnel junction sensors with high-sensitivity will greatly benefit the early diagnosis of HIV.

Selective linear etching of monolayer black phosphorus using electron beams Hot!

Yuhao Pan(潘宇浩), Bao Lei(雷宝), Jingsi Qiao(乔婧思), Zhixin Hu(胡智鑫), Wu Zhou(周武), Wei Ji(季威)
Chin. Phys. B, 2020, 29 (8): 086801 doi: 10.1088/1674-1056/ab9438
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Point and line defects are of vital importance to the physical and chemical properties of certain two-dimensional (2D) materials. Although electron beams have been demonstrated to be capable of creating single-and multi-atom defects in 2D materials, the products are often random and difficult to predict without theoretical inputs. In this study, the thermal motion of atoms and electron incident angle were additionally considered to study the vacancy evolution in a black phosphorus (BP) monolayer by using an improved first-principles molecular dynamics method. The P atoms in monolayer BP tend to be struck away one by one under an electron beam within the displacement threshold energy range of 8.55-8.79 eV, which ultimately induces the formation of a zigzag-like chain vacancy. The chain vacancy is a thermodynamically metastable state and is difficult to obtain by conventional synthesis methods because the vacancy formation energy of 0.79 eV/edge atom is higher than the typical energy in monolayer BP. Covalent-like quasi-bonds and a charge density wave are formed along the chain vacancy, exhibiting rich electronic properties. This work proposes a theoretical protocol for simulating a complete elastic collision process of electron beams with 2D layers and will facilitate the establishment of detailed theoretical guidelines for experiments on 2D material etching using focused high-energy electron beams.

Perpendicular magnetization switching by large spin—orbit torques from sputtered Bi2Te3 Hot!

Zhenyi Zheng(郑臻益), Yue Zhang(张悦), Daoqian Zhu(朱道乾), Kun Zhang(张昆), Xueqiang Feng(冯学强), Yu He(何宇), Lei Chen(陈磊), Zhizhong Zhang(张志仲), Dijun Liu(刘迪军), Youguang Zhang(张有光), Pedram Khalili Amiri, Weisheng Zhao(赵巍胜)
Chin. Phys. B, 2020, 29 (7): 078505 doi: 10.1088/1674-1056/ab9439
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Spin-orbit torque (SOT) effect is considered as an efficient way to switch the magnetization and can inspire various high-performance spintronic devices. Recently, topological insulators (TIs) have gained extensive attention, as they are demonstrated to maintain a large effective spin Hall angle (θSHeff), even at room temperature. However, molecular beam epitaxy (MBE), as a precise deposition method, is required to guarantee favorable surface states of TIs, which hinders the prospect of TIs towards industrial application. In this paper, we demonstrate that Bi2Te3 films grown by magnetron sputtering can provide a notable SOT effect in the heterostructure with perpendicular magnetic anisotropy CoTb ferrimagnetic alloy. By harmonic Hall measurement, a high SOT efficiency (8.7±0.9 Oe/(109 A/m2)) and a large θSHeff (3.3±0.3) are obtained at room temperature. Besides, we also observe an ultra-low critical switching current density (9.7×109 A/m2). Moreover, the low-power characteristic of the sputtered Bi2Te3 film is investigated by drawing a comparison with different sputtered SOT sources. Our work may provide an alternative to leverage chalcogenides as a realistic and efficient SOT source in future spintronic devices.

Dependence of mechanical properties on the site occupancy of ternary alloying elements in γ'-Ni3Al: Ab initio description for shear and tensile deformation Hot!

Minru Wen(文敏儒), Xing Xie(谢兴), Huafeng Dong(董华锋), Fugen Wu(吴福根), Chong-Yu Wang(王崇愚)
Chin. Phys. B, 2020, 29 (7): 078103 doi: 10.1088/1674-1056/ab8a38
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The site occupancy behavior of ternary alloying elements in γ'-Ni3Al (a key strengthening phase of commercial Ni-based single-crystal superalloys) can change with temperature and alloy composition owing to the effect of entropy. Using a total-energy method based on density functional theory, the dependence of tensile and shear behaviors on the site preference of alloying elements in γ'-Ni3Al were investigated in detail. Our results demonstrate that Fe, Ru, and Ir can significantly improve the ideal tensile and shear strength of the γ' phase when occupying the Al site, with Ru resulting in the strongest enhancement. In contrast, elements with fully filled d orbitals (i.e., Cu, Zn, Ag, and Cd) are expected to reduce the ideal tensile and shear strength. The calculated stress-strain relationships of Ni3Al alloys indicate that none of the alloying elements can simultaneously increase the ideal strength of the γ' phase for both Ni1-site and Ni2-site substitutions. In addition, the charge redistribution and the bond length of the alloying elements and host atoms during the tensile and shear processes are analyzed to unveil the underlying electronic mechanisms.

Modulation of carrier lifetime in MoS2 monolayer by uniaxial strain Hot!

Hao Hong(洪浩), Yang Cheng(程阳), Chunchun Wu(吴春春), Chen Huang(黄琛), Can Liu(刘灿), Wentao Yu(于文韬), Xu Zhou(周旭), Chaojie Ma(马超杰), Jinhuan Wang(王金焕), Zhihong Zhang(张智宏), Yun Zhao(赵芸), Jie Xiong(熊杰), Kaihui Liu(刘开辉)
Chin. Phys. B, 2020, 29 (7): 077201 doi: 10.1088/1674-1056/ab99ba
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Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material. The control of carrier lifetime is the key to optimizing the device function by tuning the electro-optical conversion quantum yield, carrier diffusion length, carrier collection process, etc. Till now, the prevailing modulation methods are mainly by defect engineering and temperature control, which have limitations in the modulation direction and amplitude of the carrier lifetime. Here, we report an effective modulation on the ultrafast dynamics of photoexcited carriers in two-dimensional (2D) MoS2 monolayer by uniaxial tensile strain. The combination of optical ultrafast pump-probe technique and time-resolved photoluminescence (PL) spectroscopy reveals that the carrier dynamics through Auger scattering, carrier-phonon scattering, and radiative recombination keep immune to the strain. But strikingly, the uniaxial tensile strain weakens the trapping of photoexcited carriers by defects and therefore prolongs the corresponding carrier lifetime up to 440% per percent applied strain. Our results open a new avenue to enlarge the carrier lifetime of 2D MoS2, which will facilitate its applications in high-efficient optoelectronic and photovoltaic devices.

Irradiation study of liquid crystal variable retarder for Full-disk Magneto-Graph payload onboard ASO-S mission Hot!

Jun-Feng Hou(侯俊峰), Hai-Feng Wang(王海峰), Gang Wang(王刚), Yong-Quan Luo(骆永全), Hong-Wei Li(李宏伟), Zhen-Long Zhang(张振龙), Dong-Guang Wang(王东光), Yuan-Yong Deng(邓元勇)
Chin. Phys. B, 2020, 29 (7): 074208 doi: 10.1088/1674-1056/ab8c40
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The Advanced Space-based Solar Observatory (ASO-S) is a mission proposed by the Chinese Solar Physics Community. As one of the three payloads of ASO-S, the Full-disc Magneto-Graph (FMG) will measure the photospheric magnetic fields of the entire solar disk with high spatial and temporal resolution, and high magnetic sensitivity, where liquid crystal variable retarder (LCVR) is the key to whether FMG can achieve its scientific goal. So far, there is no space flight experience for LCVR. Therefore, irradiation study for LCVRs becomes more important and urgent in order to make sure their safety and reliability in space application. In this paper, γ irradiation, proton irradiation, and ultra-violet (UV) irradiation are tested for LCVRs respectively. The optical and chemical properties during irradiation tests are measured and analyzed. For optical properties, there is no significant change in those parameters FMG payload concerned except the retardation. Although there is no drastic degradation in the retardation versus voltage during irradiations, the amount of retardation variation is much higher than the instrument requirements. Thus, an in-flight retardation versus voltage should be added in FMG payload, reducing or even avoiding the impact of retardation change. For chemical properties, the clearing point and birefringence of the LC materials almost have no change; the ion density dose not change below 60 krad[Si], but begin to increase dramatically above 60 krad[Si].

Effect of weak disorder in multi-Weyl semimetals Hot!

Zhen Ning(宁震), Bo Fu(付博), Qinwei Shi(石勤伟), Xiaoping Wang(王晓平)
Chin. Phys. B, 2020, 29 (7): 077202 doi: 10.1088/1674-1056/ab9612
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We study the behaviors of three-dimensional double and triple Weyl fermions in the presence of weak random potential. By performing the Wilsonian renormalization group (RG) analysis, we reveal that the quasiparticle experiences strong renormalization which leads to the modification of the density of states and quasiparticle residue. We further utilize the RG analysis to calculate the classical conductivity and show that the diffusive transport is substantially corrected due to the novel behavior of the quasiparticle and can be directly measured by experiments.

Improvement of valley splitting and valley injection efficiency for graphene/ferromagnet heterostructure Hot!

Longxiang Xu(徐龙翔), Wengang Lu(吕文刚), Chen Hu(胡晨), Qixun Guo(郭奇勋), Shuai Shang(尚帅), Xiulan Xu(徐秀兰), Guanghua Yu(于广华), Yu Yan(岩雨), Lihua Wang(王立华), Jiao Teng(滕蛟)
Chin. Phys. B, 2020, 29 (7): 077304 doi: 10.1088/1674-1056/ab8db2
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The valley splitting has been realized in the graphene/Ni heterostructure with the splitting value of 14 meV, and the obtained valley injecting efficiency from the heterostructure into graphene was 6.18% [Phys. Rev. B 92 115404 (2015)]. In this paper, we report a way to improve the valley splitting and the valley injecting efficiency of the graphene/Ni heterostructure. By intercalating an Au monolayer between the graphene and the Ni, the split can be increased up to 50 meV. However, the valley injecting efficiency is not improved because the splitted valley area of graphene moves away from the Fermi level. Then, we mend the deviation by covering a monolayer of Cu on the graphene. As a result, the valley injecting efficiency of the Cu/graphene/Au/Ni heterostructure reaches 10%, which is more than 60% improvement compared to the simple graphene/Ni heterostructure. Then we theoretically design a valley-injection device based on the Cu/graphene/Au/Ni heterostructure and demonstrate that the valley injection can be easily switched solely by changing the magnetization direction of Ni, which can be used to generate and control the valley-polarized current.

Facile and fast growth of high mobility nanoribbons of ZrTe5 Hot!

Jingyue Wang(王璟岳), Jingjing Niu(牛晶晶), Xinqi Li(李新祺), Xiumei Ma(马秀梅), Yuan Yao(姚湲), Xiaosong Wu(吴孝松)
Chin. Phys. B, 2020, 29 (6): 068102 doi: 10.1088/1674-1056/ab889a
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Recently, ZrTe5 has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin Hall insulator in the monolayer limit. While most of studies have been focused on the three-dimensional bulk material, it is highly desired to obtain nanostructured materials due to their advantages in device applications. We report the synthesis and characterizations of ZrTe5 nanoribbons. Via a silicon-assisted chemical vapor transport method, long nanoribbons with thickness as thin as 20 nm can be grown. The growth rate is over an order of magnitude faster than the previous method for the bulk crystals. Moreover, transport studies show that the nanoribbons are of low unintentional doping and high carrier mobility, over 30000 cm2/V·s, which enable reliable determination of the Berry phase of π in the ac plane from quantum oscillations. Our method holds great potential in growth of high quality ultra-thin nanostructures of ZrTe5.

High-resolution angle-resolved photoemission study of oxygen adsorbed Fe/MgO(001) Hot!

Mingtian Zheng, Eike F. Schwier, Hideaki Iwasawa, Kenya Shimada
Chin. Phys. B, 2020, 29 (6): 067901 doi: 10.1088/1674-1056/ab9196
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We have investigated the electronic states of clean Fe(001) and oxygen adsorbed Fe(001)-p(1×1)-O films epitaxially grown on MgO(001) substrates by means of polarization-dependent angle-resolved photoemission spectroscopy (ARPES) and extensive density-functional theory (DFT) calculations. The observed Fermi surfaces and band dispersions of pure Fe near the Fermi level were modified upon oxygen adsorption. By the detailed comparison of ARPES and DFT results of the oxygen adsorbed Fe surface, we have clarified the orbital-dependent p-d hybridization in the topmost and second Fe layers. Furthermore, the observed energy levels and Fermi wave numbers for the oxygen adsorbed Fe surface were deviated from the DFT calculations depending on the orbital characters and momentum directions, indicating an anisotropic interplay of the electron correlation and p-d hybridization effects in the surface region.
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