18 results on '"Yanfeng GUO"'
Search Results
2. Manipulating the charge density wave state in kagome compound RbV3Sb5
- Author
-
Yu-Xin Meng, Cheng-Long Xue, Li-Guo Dou, Wei-Min Zhao, Qi-Wei Wang, Yong-Jie Xu, Xiangqi Liu, Wei Xia, Yanfeng Guo, and Shao-Chun Li
- Subjects
General Physics and Astronomy - Abstract
Owing to the unique electronic structure, kagome materials AV3Sb5 (A=K, Rb, Cs) provide a fertile platform of quantum phenomena such as the strongly correlated state and topological Dirac band. It is well known that RbV3Sb5 exhibits a 2×2 unconventional charge density wave (CDW) state at low temperature, and the mechanism is controversial. Here, by using scanning tunneling microscopy/spectroscopy (STM/STS), we successfully manipulated the CDW state in the Sb plane of RbV3Sb5, and realized a new √ 3×√ 3 modulation together with the ubiquitous 2×2 period in the CDW state of RbV3Sb5. The work provides a new understanding of the collective quantum ground states in the kagome materials.
- Published
- 2023
3. Doping tuned anomalous Hall effect in the van der Waals magnetic topological phases Mn(Sb1-x Bi x )4Te7
- Author
-
Xin Zhang, Zhicheng Jiang, Jian Yuan, Xiaofei Hou, Xia Wang, Na Yu, Zhiqiang Zou, Zhengtai Liu, Wei Xia, Zhenhai Yu, Dawei Shen, and Yanfeng Guo
- Subjects
General Physics and Astronomy - Abstract
The van der Waals (vdW) MnSb4Te7 is a newly synthesized antiferromagnetic (AFM) topological insulator hosting robust axion insulator state irrelative of the specific spin structure. However, the intrinsic hole doped character of MnSb4Te7makes the Fermi level far away from the Dirac point of about 180 meV, which is unfavorable for the exploration of exotic topological properties such as the quantum anomalous Hall effect (QAHE). To shift up the Fermi level close to the Dirac point, the strategy by partially replacing Sb by Bi as Mn(Sb1-x Bi x )4Te7 was tried and the magnetotransport properties, in particularly, the anomalous Hall effect, were measured and analyzed. Through the electron doping, the anomalous Hall conductance σ AHchanges from negative to positive between x = 0.3 and 0.5, indicative of a possible topological transition. Besides, a charge neutrality point (CNP) also appears between x = 0.6 and 0.7. The results would be instructive for further understanding the interplay between nontrivial topological states and the magnetism, as well as for the exploration of exotic topological properties.
- Published
- 2023
4. X-ray spectroscopy for the magnetic study of the van der Waals ferromagnet CrSiTe3 in the few- and monolayer limit
- Author
-
Ryuji Fujita, Jieyi Liu, Xiaofei Hou, Yanfeng Guo, Javier Herrero-Martín, Gerrit van der Laan, and Thorsten Hesjedal
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,General Chemistry ,Condensed Matter Physics - Abstract
The study of magnetic order in few- and monolayer van der Waals materials poses a challenge to the most commonly employed magnetic characterization techniques as they normally lack magnetic sensitivity and/or lateral resolution enabling their thickness-dependent probing. Here we demonstrate the usefulness of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements, carried out at the Cr L 2 , 3 and Te M 5 edges, for the study of the ferromagnetic semiconductor CrSiTe3 (CST) in the form of single- and few-layer flakes. By scanning the sample under the incident x-ray beam, a map of the exfoliated system was obtained, which reproduced the optical micrographs showing the detailed distribution and thicknesses of the flakes. In this way, XAS/XMCD was performed at selected sample areas, revealing the thickness-resolved spectroscopic and magnetic properties of the flakes, such as the spin and orbital magnetic moments. The spin moment, in line with the saturation field, is decreasing with film thickness, revealing a single-domain and out-of-plane magnetization for the thinnest films. For CST, the electronic properties are governed by the strong covalent bond between the Cr 3d(e g ) and Te 5p states, giving rise to a superexchange scenario. We observed a gradually increasing ratio of orbital to spin moment for thinner flakes, which could be due to a further increase of the covalent mixing. Hysteresis loops were recorded at the Cr L 3 edge, showing an open loop for 10 down to ∼3 layers, while the bulk shows a wasp-waist shaped loop. With the transition temperature from the soft to the hard ferromagnetic state decreasing with thickness, the monolayer shows a narrowed, closed loop at 10 K, suggesting its transition temperature > 10 K. Our study demonstrates the unique capabilities of XAS/XMCD for the study of few-layer van der Waals magnets, highlighting the interplay between electron correlation and ferromagnetism in CST.
- Published
- 2022
5. Electronic structure and layer-dependent magnetic order of a new high-mobility layered antiferromagnet KMnBi
- Author
-
Yichen Yang, Hengzhe Lu, Jian Yuan, Zhengtai Liu, Zhicheng Jiang, Zhe Huang, Jianyang Ding, Jiayu Liu, Soohyun Cho, Jishan Liu, Zhonghao Liu, Yanfeng Guo, Yi Zheng, and Dawei Shen
- Subjects
General Materials Science ,Condensed Matter Physics - Abstract
Room-temperature two-dimensional antiferromagnetic (AFM) materials are highly desirable for various device applications. In this letter, we report the low-energy electronic structure of KMnBi measured by angle-resolved photoemission spectroscopy, which confirms an AFM ground state with the valence band maximum located at −100 meV below the Fermi level and small hole effective masses associated with the sharp band dispersion. Using complementary Raman, atomic force microscope and electric transport measurement, we systematically study the evolution of electric transport characteristics of micro-mechanically exfoliated KMnBi with varied flake thicknesses, which all consistently reveal the existence of a probable AFM ground state down to the quintuple-layer regime. The AFM phase transition temperature ranges from 220 K to 275 K, depending on the thickness. Our results suggest that with proper device encapsulation, multilayer KMnBi is indeed a promising 2D AFM platform for testing various theoretical proposals for device applications.
- Published
- 2023
6. A new transition metal diphosphide α-MoP2 synthesized by a high-temperature and high-pressure technique
- Author
-
Xiaolei Liu, Zhenhai Yu, Jianfu Li, Zhenzhen Xu, Chunyin Zhou, Zhaohui Dong, Lili Zhang, Xia Wang, Na Yu, Zhiqiang Zou, Xiaoli Wang, and Yanfeng Guo
- Subjects
General Physics and Astronomy - Abstract
Monoclinic α-MoP2, with the OsGe2-type structure (space group C2/m, Z = 4) and lattice parameters a = 8.7248(11) Å, b = 3.2322(4) Å, c = 7.4724(9)Å, and β = 119.263°, was synthesized under a pressure of 4~GPa at a temperature between 1100 °C and 1200 °C. The structure of α-MoP2 and its relationship to other transition metal diphosphides are discussed. Surprisingly, the ambient pressure phase orthorhombic β-MoP2 (space group Cmc21) is denser in structure than α-MoP2. Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition from β-MoP2 to α-MoP2, suggesting that α-MoP2 is a stable phase at ambient conditions; this is also supported by the total energy and phonon calculations.
- Published
- 2023
7. High-pressure study of topological semimetals XCd2Sb2 (X = Eu and Yb)
- Author
-
Chuchu Zhu, Hao Su, Erjian Cheng, Lin Guo, Binglin Pan, Yeyu Huang, Jiamin Ni, Yanfeng Guo, Xiaofan Yang, and Shiyan Li
- Subjects
General Physics and Astronomy - Abstract
Topological materials have aroused great interest in recent years, especially when magnetism is involved. Pressure can effectively tune the topological states and possibly induce superconductivity. Here we report the high-pressure study of topological semimetals XCd2Sb2 (X = Eu and Yb), which have the same crystal structure. In antiferromagnetic (AFM) Weyl semimetal EuCd2Sb2, the Néel temperature (T N) increases from 7.4 K at ambient pressure to 50.9 K at 14.9 GPa. When pressure is above 14.9 GPa, the AFM peak of resistance disappears, indicating a non-magnetic state. In paramagnetic Dirac semimetal candidate YbCd2Sb2, pressure-induced superconductivity appears at 1.94 GPa, then T c reaches to a maximum of 1.67 K at 5.22 GPa and drops to zero at about 30 GPa, displaying a dome-shaped temperature–pressure phase diagram. High-pressure x-ray diffraction measurement demonstrates that a crystalline-to-amorphous phase transition occurs at about 16 GPa in YbCd2Sb2, revealing the robustness of pressure-induced superconductivity against structural instability. Similar structural phase transition may also occur in EuCd2Sb2, causing the disappearance of magnetism. Our results show that XCd2Sb2 (X = Eu and Yb) is a novel platform for exploring the interplay among magnetism, topology, and superconductivity.
- Published
- 2022
8. Nontrivial Topological States in BaSn5 Superconductor Probed by de Haas–van Alphen Quantum Oscillations
- Author
-
Lixuesong Han, Xianbiao Shi, Jinlong Jiao, Zhenhai Yu, Xia Wang, Na Yu, Zhiqiang Zou, Jie Ma, Weiwei Zhao, Wei Xia, and Yanfeng Guo
- Subjects
Superconductivity (cond-mat.supr-con) ,Condensed Matter - Superconductivity ,Condensed Matter::Superconductivity ,FOS: Physical sciences ,General Physics and Astronomy - Abstract
We report herein the nontrivial topological states in an intrinsic type-II superconductor BaSn5 (Tc ~ 4.4 K) probed via measuring the magnetizations, specific heat, de Haas-van Alphen (dHvA) effect and performing first principles calculations. The first principles calculations reveal a topological nodal ring structure centering at the H point in the kz = {\pi} plane of the Brillouin zone (BZ), which could be gapped by spin-orbit coupling (SOC), yielding rather small gaps below and above the Fermi level about 0.04 eV and 0.14 eV, respectively. The SOC also results in a pair of Dirac points along the {\Gamma}-A direction and located ~ 0.2 eV above the Fermi level. The analysis of the dHvA quantum oscillations supports the calculations by revealing nontrivial Berry phase originated from three hole and one electron pockets related to the bands forming the Dirac cones. Our study thus provides an excellent avenue for investigating the interplay between superconductivity and nontrivial topological states., Comment: 15 pages, 6 figures, 1 tables
- Published
- 2022
9. Measurement of electronic structure in van der Waals ferromagnet Fe5–x GeTe2
- Author
-
Kui Huang, Zhenxian Li, Deping Guo, Haifeng Yang, Yiwei Li, Aiji Liang, Fan Wu, Lixuan Xu, Lexian Yang, Wei Ji, Yanfeng Guo, Yulin Chen, and Zhongkai Liu
- Subjects
General Physics and Astronomy - Abstract
As a van der Waals ferromagnet with high Curie temperature, Fe5–x GeTe2 has attracted tremendous interests recently. Here, using high-resolution angle-resolved photoemission spectroscopy (ARPES), we systematically investigated the electronic structure of Fe5–x GeTe2 crystals and its temperature evolution. Our ARPES measurement reveals two types of band structures from two different terminations with slight kz evolution. Interestingly, across the ferromagnetic transition, we observed the merging of two split bands above the Curie temperature, suggesting the band splitting due to the exchange interaction within the itinerant Stoner model. Our results provide important insights into the electronic and magnetic properties of Fe5–x GeTe2 and the understanding of magnetism in a two-dimensional ferromagnetic system.
- Published
- 2022
10. Observation of large in-plane anisotropic transport in van derWaals semiconductor Nb2SiTe4 *
- Author
-
Jiangang Guo, Yanfeng Guo, Liwei Guo, Kaiyao Zhou, Long Chen, Jun Deng, Yang Yang, and Wei Xia
- Subjects
In plane ,Semiconductor ,Materials science ,Condensed matter physics ,business.industry ,General Physics and Astronomy ,Anisotropy ,business - Abstract
Two-dimensional (2D) van der Waals material is a focus of research for its widespread application in optoelectronics, memories, and spintronics. The ternary compound Nb2SiTe4 is a van der Waals semiconductor with excellent air stability and small cleavage energy, which is suitable for preparing a few layers counterpart to explore novel properties. Here, properties of bulk Nb2SiTe4 with large in-plane electrical anisotropy are demonstrated. It is found that hole carriers dominate at a temperature above 45 K with a carrier active energy of 31.3 meV. The carrier mobility measured at 100 K is about 213 cm2⋅V−1⋅s−1 in bulk Nb2SiTe4, higher than the reported results. In a thin flake Nb2SiTe4, the resistivity ratio between the crystalline axes of a and b is reaching about 47.3 at 2.5 K, indicating that there exists a large anisotropic transport behavior in their basal plane. These novel transport properties provide accurate information for modulating or utilizing Nb2SiTe4 for electronic device applications.
- Published
- 2021
11. Measurement of Superconductivity and Edge States in Topological Superconductor Candidate TaSe3
- Author
-
Zhong-Kai Liu, Yulin Chen, Yanfeng Guo, Lexian Yang, Shuai Liu, Hongtao Yuan, Yanpeng Qi, Simin Nie, and Mei-Xiao Wang
- Subjects
Superconductivity ,Physics ,Condensed matter physics ,Condensed Matter::Superconductivity ,General Physics and Astronomy ,Edge states - Abstract
Topological superconductors (TSCs) have been widely investigated in recent years due to their novel physics and ability to host Majorana fermions (MFs) which are key to topological quantum computation. Despite the great interest, only a few compounds have been proposed as candidates of intrinsic TSCs, such as iron-based superconductor FeSe0.55Te0.45 and 2M-WS2. Among them, quasi-one-dimensional superconductor TaSe3 possesses fascinating properties such as its simple stoichiometry, layered nature and chemical stability. Here, using scanning tunneling microscope/spectroscopy (STM/STS), we systematically investigate the topography and electronic structure of TaSe3. Our STM/STS measurement reveals large atomically flat, defect-free surfaces suitable for the search of MF; electronic density of states consistent with our angle-resolved photoemission result and band-structure calculations, and a uniform superconducting gap with a typical size of ∼ 0.25 meV. Remarkably, additional edge states are observed in the vicinity of the terrace edge, suggesting they may have a topological origin. Our result proves the coexistence of superconductivity and topological electronic structure in TaSe3, making it an intriguing platform to investigate topological superconductivity.
- Published
- 2021
12. Determination of the surface states from the ultrafast electronic states in a thermoelectric material
- Author
-
Weidong Luo, Yuanyuan Yang, Hongyuan Wang, Tongyao Wu, Shaofeng Duan, Wentao Zhang, Yanfeng Guo, Chaozhi Huang, and Tianwei Tang
- Subjects
Materials science ,business.industry ,General Physics and Astronomy ,Optoelectronics ,Condensed Matter::Strongly Correlated Electrons ,business ,Thermoelectric materials ,Ultrashort pulse ,Electronic states ,Surface states - Abstract
We reveal the electronic structure in YbCd2Sb2, a thermoelectric material, by angle-resolved photoemission spectroscopy (ARPES) and time-resolved ARPES (trARPES). Specifically, three bulk bands at the vicinity of the Fermi level are evidenced near the Brillouin zone center, consistent with the density functional theory (DFT) calculation. It is interesting that the spin-unpolarized bulk bands respond unexpectedly to right- and left-handed circularly polarized probe. In addition, a hole band of surface states, which is not sensitive to the polarization of the probe beam and is not expected from the DFT calculation, is identified. We find that the non-equilibrium quasiparticle recovery rate is much smaller in the surface states than that of the bulk states. Our results demonstrate that the surface states can be distinguished from the bulk ones from a view of time scale in the nonequilibrium physics.
- Published
- 2021
13. de Haas-van Alphen Quantum Oscillations in BaSn3 Superconductor with Multiple Dirac Fermions*
- Author
-
Hao Su, Xia Wang, Zhiqiang Zou, Yanfeng Guo, Wei Xia, Leiming Chen, Xianbiao Shi, Xiaolei Liu, Na Yu, Gaoning Zhang, and Weiwei Zhao
- Subjects
Superconductivity ,Physics ,Condensed matter physics ,Fermi level ,Dirac (software) ,General Physics and Astronomy ,Quantum oscillations ,Fermi surface ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Brillouin zone ,symbols.namesake ,Dirac fermion ,Geometric phase ,0103 physical sciences ,symbols ,010306 general physics ,0210 nano-technology - Abstract
Characterization of Fermi surface of the BaSn3 superconductor (T c ∼ 4.4 K) by de Haas–van Alphen (dHvA) effect measurement reveals its non-trivial topological properties. Analysis of non-zero Berry phase is supported by the ab initio calculations, which reveals a type-II Dirac point setting and tilting along the high symmetric K–H line of the Brillouin zone, about 0.13 eV above the Fermi level, and other two type-I Dirac points on the high symmetric Γ–A direction, but slightly far below the Fermi level. The results demonstrate BaSn3 as an excellent example hosting multiple Dirac fermions and an outstanding platform for studying the interplay between nontrivial topological states and superconductivity.
- Published
- 2020
14. A New Effect of Oxygen Plasma on Two-Dimensional Field-Effect Transistors: Plasma Induced Ion Gating and Synaptic Behavior*
- Author
-
Wei Xia, Bin-Bin Wang, Yanfeng Guo, Jiamin Xue, and Chenglei Guo
- Subjects
Capacitive coupling ,Materials science ,business.industry ,Transistor ,General Physics and Astronomy ,02 engineering and technology ,Plasma ,Gating ,Dielectric ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Ion ,Hysteresis ,law ,0103 physical sciences ,Optoelectronics ,Field-effect transistor ,010306 general physics ,0210 nano-technology ,business - Abstract
Plasma treatment is a powerful tool to tune the properties of two-dimensional materials. Previous studies have utilized various plasma treatments on two-dimensional materials. We find a new effect of plasma treatment. After controlled oxygen-plasma treatment on field-effect transistors based on two-dimensional SnSe 2 , the capacitive coupling between the silicon back gate and the channel through the 300nm SiO 2 dielectric can be dramatically enhanced by about two orders of magnitude (from 11 nF/cm 2 to 880 nF/cm 2 ), reaching good efficiency of ion-liquid gating. At the same time, plasma treated devices show large hysteresis in the gate sweep demonstrating memory behavior. We reveal that this spontaneous ion gating and hysteresis are achieved with the assistance of a thin layer of water film automatically formed on the sample surface with water molecules from the ambient air, due to the change in hydrophilicity of the plasma treated samples. The water film acts as the ion liquid to couple the back gate and the channel. Thanks to the rich carrier dynamics in plasma-treated two-dimensional transistors, synaptic functions are realized to demonstrate short- and long-term memories in a single device. This work provides a new perspective on the effects of plasma treatment and a facile route for realizing neuromorphic devices.
- Published
- 2019
15. Tunnelling current in YBa2Cu3O7−δ/Nb-doped SrTiO3heterojunctions
- Author
-
Yanfeng Guo, M Lei, Weihua Tang, Jingqin Shen, Peigang Li, Li Chen, and X. Guo
- Subjects
Materials science ,Acoustics and Ultrasonics ,Condensed matter physics ,business.industry ,Doping ,Mineralogy ,Heterojunction ,Semiconductor device ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Tunnel effect ,Semiconductor ,Depletion region ,business ,Quantum tunnelling ,Diode - Abstract
We report the fabrication of YBa2Cu3O7−δ/Nb-doped (0.8 wt%) SrTiO3 p–n junctions by pulsed electron deposition, photolithography and Ar-ion etching techniques. In the junctions, the abnormal rectifying behaviour and the Esaki tunnelling diode-like characteristic have been observed above and below the superconducting transition temperature TC of YBa2Cu3O7−δ, respectively. The tunnelling process is responsible for these behaviours and the depletion layer formed at the junction interface with very low resistance is the dominating factor. The intriguing properties in this work indicate that it is possible to realize the functions of traditional semiconductor diodes by using high-temperature superconductor-based heterojunctions.
- Published
- 2007
16. Magnetic and electrical properties of antiperovskite Mn3InN synthesized by a high-pressure method
- Author
-
Jun Li, Yanfeng Guo, S. B. Zhang, Wei Yi, Clastin I. Sathish, Kazunari Yamaura, Alexei A. Belik, Ying Sun, and Xia Wang
- Subjects
History ,Magnetization ,Antiperovskite ,Paramagnetism ,Materials science ,Spintronics ,Condensed matter physics ,Ferromagnetism ,Magnetism ,Antiferromagnetism ,Magnetic susceptibility ,Computer Science Applications ,Education - Abstract
Mn3InN antiperovskite is synthesized under high-pressure conditions, followed by measurements of magnetic susceptibility, isothermal magnetization, electrical resistivity, and specific heat. Multiple magnetic interactions are observed between 2 K and 400 K: the paramagnetic state turns to an antiferromagnetic state at 300 K on cooling, and a weak ferromagnetic contribution appears at 175 K by further cooling. Below 50 K, an enhanced ferromagnetic contribution is obvious. Although a long-range antiferromagnetic order is clearly established at room temperature, the material retains a good metallic conduction over a wide temperature range (the Sommerfeld coefficient is 43.3 mJ mol−1 K−2), suggesting a possible use of the material in spintronics applications.
- Published
- 2012
17. Essential difference between scatterings by Zn and Pt on superconductivity of BaFe1.92Pt0.08As2single crystal
- Author
-
Eiji Takayama-Muromachi, Yanfeng Guo, S. B. Zhang, Xia Wang, Alexei A. Belik, Kazunari Yamaura, and Jun Li
- Subjects
Superconductivity ,History ,Crystallography ,Materials science ,Condensed matter physics ,Scattering ,Condensed Matter::Superconductivity ,Lattice (order) ,Doping ,Single crystal ,Computer Science Applications ,Education - Abstract
We report a Zn-doping effect on BaFe1.92Pt0.08As2 (Tc =24.5 K) single crystal. Tc rapidly decreases with increasing the Zn content in the lattice, revealing a distinct feature which is highly contrasted with the intrinsic scattering feature induced by Pt. Doped Zn completely kills the superconductivity by no more than 8 atomic %, while intrinsic scattering induced by doped Pt shows a good coexistence with the superconductivity. The results are discussed in connection with the s±- and s++-wave models.
- Published
- 2012
18. Nuclear spin-lattice relaxation rate in the superconducting state on La(Fe1−xZnx)AsO0.85studied by75As-NMR
- Author
-
Youguo Shi, Keiichi Ishida, Tetsuya Iye, Yoshio Nakai, Eiji Takayama-Muromachi, Yanfeng Guo, Susumu Kitagawa, and Kazunari Yamaura
- Subjects
Superconductivity ,History ,Condensed matter physics ,Lattice Relaxation Rate ,Chemistry ,Relaxation rate ,State (functional analysis) ,Computer Science Applications ,Education - Abstract
75As nuclear spin-lattice relaxation rate 1/T1 was measured in Zn-free and Zn-substituted La(Fe1−xZnx)AsO0.85 (x = 0, and 0.05), Tc of which is 25 K and 0 K, respectively. Although the temperature dependence of 1/T1T above Tc is the same between two samples, 1/T1T of x = 0 shows T3.0±0.1 dependence (1/T1 ∝ T4) in the superconducting (SC) state, but 1/T1T of non-SC x = 0.05 sample continuously decreases below 50 K. The normalized 1/T1T [(1/T1T)x=0/(1/T1T)x=0.05], which is related to the SC gap structure, is proportional to T2.4±0.1 below Tc. These results indicate that the temperature dependence of 1/T1T in the SC state can be affected by the temperature dependence of the normal-state 1/T1T.
- Published
- 2012
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.