Showing papers by "Guodong Liu published in 2022"
TL;DR: In this paper , the structure, stability, mechanical and electronic properties, and potential applications on carbon-based pentagonal materials with binary compositions, namely, Penta-CnX6n (n = 1, 2, 4, 5; X = B, N, Al, Si, P, Ga, Ge, As).
Abstract: Since the discovery of penta-graphene, two-dimensional (2-D) pentagonal-structured materials have been highly expected to have desirable performance because of their unique structures and accompanied physical properties. Hence, based on the first-principles calculations, we performed a systematical study on the structure, stability, mechanical and electronic properties, and potential applications on carbon-based pentagonal materials with binary compositions, namely, Penta-CnX6-n (n = 1, 2, 4, 5; X = B, N, Al, Si, P, Ga, Ge, As). We found that eleven out of thirty-two Penta-CnX6-n have good stability and can be further studied. Among them, two materials, namely, Penta-C4P2 and Penta-C5P are metallic, and others are indirect band gap semiconductors, whose band gaps calculated by the HSE06 functional are in the range of 1.37-6.43 eV, covering the infrared-visible-ultraviolet regions. Furthermore, we found that metallic Penta-CnX6-n can become promising anode materials for Na-ion batteries (NIBs) with high storage capacity, while some semiconducting Penta-CnX6-n can become excellent water splitting photocatalysts. In addition, Penta-C4P2 and Penta-C2Al4 were found to have obvious in-plane negative Poisson's ratio (NPR) of -0.083 and -0.077, respectively. More interestingly, we found that Penta-C2Al4 exhibits a peculiar in-plane half negative Poisson's ratio (H-NPR) with the fundamental mechanism clarified. These outstanding performances endow binary pentagonal materials with excellent application prospects.
11 citations
TL;DR: In this paper, a linear relationship between the length of Fermi arcs and Gibbs free energy (ΔGH*) has been found, which not only provides the direct evidence to link the enhanced catalytic performance and surface Fermion arc states, but also fully clarifies the fundamental mechanism in topological catalysis.
Abstract: Topological materials have been recently regarded as ideal catalysts for heterogeneous reactions due to their surface metallic states and high carrier mobility. However, the underlying relationship between their catalytic performance and topological states is under debate. It has been discovered that the electride 12CaO·7Al2O3 (C12A7:4e−) hosts multifold fermions and Fermi arcs on the (001) surface near the Fermi level due to the interstitial electrons. Through the comparison of catalytic performance under different doping and strain conditions, based on the hydrogen evolution process, it has been demonstrated that the excellent catalytic performance indeed originates from topological properties. A linear relationship between the length of Fermi arcs, and Gibbs free energy (ΔGH*) has been found, which not only provides the direct evidence to link the enhanced catalytic performance and surface Fermi arc states, but also fully clarifies the fundamental mechanism in topological catalysis.
11 citations
TL;DR: In this article , the authors focus on a phononic topological category that features higher-order nodal points in two-dimensional (2D) systems and reveal the mechanism for the band structure deforming, such as the tilting of the QNP cone and the warping of constant frequency surfaces.
Abstract: Fermionic quasiparticles in solids have attracted tremendous attention in the last decades. The conceptual framework of quasiparticles has recently been extended to bosonic systems, especially the phononic one. In this work we focus on a peculiar phononic topological category that features higher-order nodal points in two-dimensional (2D) systems. By searching through the total 80 layer groups, we find that the rotation symmetry (except the twofold one) combined with the time-reversal symmetry could support the presence of higher-order nodal points. We further find that the highest order of momentum in the 2D system is the second order, dubbed as quadratic nodal point (QNP). We show that the 2D QNP can be characterized by an integer topological invariant, demonstrated by the presence of edge states. Remarkably, this work reveals the mechanism for the band structure deforming, such as the tilting of the QNP cone and the warping of constant frequency surfaces. The work paves the way to study the higher-order nodal point in phononic systems, and several candidate materials are also provided.
10 citations
TL;DR: In this article , the authors reported the perfect combination of half-metallicity and electronic topological properties in single 2D phase, namely, the PrOBr monolayer, which only possesses conducting electrons in the spin-up channel, while it shows a large insulating gap of 3.5 eV in the Spindown channel with the Curie temperature as high as 423 K.
Abstract: Two-dimensional (2D) half metallicity and topological aspects of matter are the focus of current research because of the promising applications in nanoscale spintronics and quantum electronics. In this work, we report the perfect combination of half-metallic properties and electronic topological properties in single 2D phase, namely, the PrOBr monolayer. The material only possesses conducting electrons in the spin-up channel, while it shows a large insulating gap of 3.5 eV in the spin-down channel with the Curie temperature as high as 423 K. In the conducting spin channel, it exhibits multiple band crossings, which can surprisingly realize the coexistence of fully spin-polarized open/closed, and type-I/type-II/hybrid-type nodal lines. The coexistence of so many nodal line states has been neither identified in 2D materials nor identified in half metals before. The protection mechanism, the spin-orbit coupling impact, and the effective models for the nodal lines have been clarified. Our results suggest that the PrOBr monolayer is a good electronic material with (i) 2D half metallicity; (ii) multiple nodal lines of 100% spin polarization.
6 citations
TL;DR: A review of the background, motivation, investigation process, and fundamental mechanisms of topological catalysts can be found in this article , covering the Weyl, Dirac, multiple nodal point, and nodal line categories.
Abstract: This work provides a timely review of the background, motivation, investigation process, and fundamental mechanisms of topological catalysts, fully covering the Weyl, Dirac, multiple nodal point, and nodal line categories.
5 citations
TL;DR: In this paper , the authors conduct an exhaustive search of all 230 space groups (SGs), finding that six SGs host C-2 semimetals at high-symmetry points (HSPs) and nine SGs hosts the C- 2 DPs on their high symmetry lines (HSLs).
Abstract: Topological Dirac semimetals have been attracting considerable attention. Recently, a new class of Dirac points with a topological charge of $\ifmmode\pm\else\textpm\fi{}2$, named charge-2 Dirac points (C-2 DPs), were proposed in spinless systems. In this paper, we conduct an exhaustive search of all 230 space groups (SGs), finding that six SGs host C-2 DP at high-symmetry points (HSPs) and nine SGs host the C-2 DP on their high-symmetry lines (HSLs). Based on the symmetry analysis, we find the lowest symmetry requirements that enforce a C-2 DP and construct the corresponding effective models. Furthermore, we investigate the difference between C-2 DPs at HSPs and on HSLs, finding that the type-II C-2 DP only appears on HSLs. Via the first-principles calculations, we identify the corresponding realistic materials that host C-2 DPs. Therefore, our paper not only offers the guidelines to identify the materials that host C-2 DPs in spinless systems based on symmetry requirements, but also paves the effective way to study the C-2 DPs in spinless systems.
5 citations
TL;DR: In this article, the topological properties of electrides give rise to a boost to their performance in topological states, in which excess electrons are weakly bounded by lattice interstitial position.
Abstract: Electrides, in which excess electrons are weakly bounded by lattice interstitial position, are suitable for achieving topological states. The topological properties of electrides give rise to a boost to their...
3 citations
3 citations
TL;DR: Based on first-principles calculations and crystal symmetry analysis, the authors presented a lot of materials with fully spin-polarized nodal boxes in a ferromagnetic cubic structure.
Abstract: Magnetic topological materials have attracted much attention because of their exotic topological quantum physics arising from the interplay between spintronics, crystallography, magnetism, and topology. Based on first-principles calculations and crystal symmetry analysis, we present a lot of materials with fully spin-polarized nodal boxes in a ferromagnetic cubic structure. This nodal box is formed by six butterflylike nodal lines in the Brillouin zone when neglecting the weak spin-orbit coupling (SOC) mainly from F atoms. Such a fully spin-polarized nodal box is reported here. The ${M}_{110}$ mirror symmetry is not broken in [110] magnetization direction, thus leaving a symmetrically protected butterflylike nodal line on the (110) surface when the SOC is present. The band gaps of the nodal box induced by SOC are less than 1 meV due to the weak SOC effect. Our discovery fills the gap in the study of a fully spin-polarized nodal box in the magnetic system and provides a good research platform for studying the combination of new topological states and spintronics. Such a fully spin-polarized nodal box with unique Fermi surfaces and surface states traversing the Brillouin zone holds great promise for applications in catalysis and spin transport.
3 citations
TL;DR: Wang et al. as mentioned in this paper found that 27 of 80 nonmagnetic layer groups contain spin-orbit Dirac points (SODPs), and screen 65 actual materials from the huge 2D inorganic crystal database (6351).
3 citations
TL;DR: In this paper , the effects of various molar flow ratios on the surface morphology, crystalline quality, material straining, and optical properties of heteroepitaxial AlN thin films were studied using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and photoluminescence (PL).
Abstract: The epitaxial aluminum nitride (AlN) crystals were grown on c-plane sapphire using high-temperature metal nitride vapor phase epitaxy at the source materials’ different molar flow ratios (V/III ratios). The effects of various V/III ratios on the surface morphology, crystalline quality, material straining, and optical properties of heteroepitaxial AlN thin films were studied using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and photoluminescence (PL). With the increase in the V/III ratio from 1473 to 7367, the substrate surface underwent changes that vary from whiskers to three-dimensional island structures, two-dimensional layered stack structures, and stacked sheet structures. Additionally, due to the presence of nanoscale pits on the substrate surface, almost all samples were tensile stressers. The PL spectra demonstrated the defect luminescence of the epitaxial films, indicating that nitrogen vacancies and oxygen impurities were the samples’ main defects.
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TL;DR: In this paper , the authors have observed two sets of nodal surfaces and the formation of two homocentric nodal ring states in NaAlSi by performing high-resolution angle-resolved photoemission measurements and band structure calculations.
Abstract: The discovery of the topological states has become a key topic in condensed matter physics with the focus evolving from the Dirac or Weyl points to high-dimension topological states of the nodal lines and nodal surfaces. For a topological material to manifest its quantum properties and become useful in applications, the topological states need to be genuine and clean so that they lie close to the Fermi level without other trivial bands existing at the Fermi level. While a number of high-dimension topological materials are predicted, only a few of them have been synthesized and confirmed and the genuine and clean ones are especially scarce. Here we report the realization of the genuine clean multiple high-dimension topological states in NaAlSi. By performing high-resolution angle-resolved photoemission measurements and band structure calculations, we have observed two sets of nodal surfaces and the formation of two homocentric nodal ring states in NaAlSi. The observed nodal rings are distinct in that the inner one is a type-{\uppercase\expandafter{\romannumeral1}} nodal ring while the outer one is a type-{\uppercase\expandafter{\romannumeral1}} nodal ring embedded with four type-{\uppercase\expandafter{\romannumeral3}} nodal points. All the bands involved in the nodal rings lie very close to the Fermi level with no other trivial bands coexisting at the Fermi level. These observations make NaAlSi a desirable topological material to explore for novel quantum states and exotic properties.
TL;DR: Li et al. as mentioned in this paper investigated Li adsorption and diffusion on graphene with vacancy defects of different sizes, namely GVn (n = 2, 4, 6, 10, and 13), and showed that these defective structures can adsorb Li atoms stably and dispersedly.
Abstract: For lithium-ion batteries (LIBs), the dilemma of low-capacity commercial graphite electrode has forced researchers to keep developing high-capacity electrodes. While two-dimensional (2-D) carbon materials are widely used in the field of energy storage due to their excellent physical and chemical properties. Here, based on density functional theory, we systematically investigate Li adsorption and diffusion on graphene with vacancy defects of different sizes, namely GVn (n = 2, 4, 6, 10, and 13). Our results show that, unlike pristine graphene, these defective structures can adsorb Li atoms stably and dispersedly. The adsorption energy of Li gradually enhances as it approaches the vacancy defects. Furthermore, the diffusion of Li on the surfaces of the GVn (n = 6, 10, and 13) is more difficult due to the presence of large vacancy defects. Fortunately, when their vacancy defects are filled with Li atoms, the corresponding diffusion barriers would decrease dramatically. What is most interesting is that as the size of vacancy defect increases, its corresponding Li storage capacity also increases considerably. The calculated storage capacities of GV10 and GV13 are 614 mA h g−1 and 637 mA h g−1, respectively, which exceed that of conventional graphite electrode and many other 2-D graphene-like electrodes. Thus, we believed that is an interesting and competitive example for developing high-capacity electrodes.
TL;DR: In this article , a family of 2D hexagonal materials, XH (X = Si, Ge, Sn), is shown to have ideal linear nodal points (LNPs) and quadratic phononic nodal point (QNPs), connecting by an edge arc.
Abstract: Topological phases in two-dimensional (2D) systems have been attracting tremendous attention since the discovery of graphene. Since the experimental probing could proceed in the whole phonon spectrum, intensive research effort has been devoted to the topological quantum phases in phononic systems. Via first-principles calculations, we predict that a family of 2D hexagonal materials, XH (X = Si, Ge, Sn), hosts ideal linear nodal points (LNPs) and quadratic phononic nodal points (QNPs). Specifically, the LNPs appear at the two inequivalent valleys, akin to the 2D Dirac point in graphene, connecting by an edge arc. The QNP is pinned at the Γ point, two edge states emerge from their projections. Remarkably, both LNPs and QNP enjoy an emergent chiral symmetry, we then show that they feature nontrivial topological charges. As a consequence, our work discusses the nodal points in the phonon spectrum of 2D materials and provides ideal candidates to study the topology for bosonic systems.
TL;DR: In this paper , the influence of the Cu/In molar ratio of CuInSe2 quantum dots on Cu-related defects and photo-physical properties was discussed. But the authors did not consider the effect of different defect types.
Abstract: Quantum dots of I–III–VI ternary compounds exhibit unusual photophysical properties and technological utility, which attract attention and have been intensely investigated. CuInSe2 quantum dots are an environmentally friendly composition, a direct transition, and an adjustable bandgap. Here, we discuss the influence of the Cu/In molar ratio of CuInSe2 quantum dots on Cu-related defects and photo-physical properties, and CuInSe2 quantum dots are synthesized by a green, safe, and low-temperature method in triethylene glycol. The proportion of the +1 and +2 oxidation states of Cu in the quantum dots will change with the Cu/In molar atomic ratio. The +1-oxidation state of Cu will prolong the carrier recombination lifetime and provide favorable conditions for the transfer and collection of carriers. By adjusting for different defect types, we can better apply CISe quantum dots in devices and other fields.
20 Jan 2022
TL;DR: Yan et al. as discussed by the authors proposed a strongly coupled quantum-means-coupled quantum-matter physics (SQMPP) model for superconductivity and showed that strong coupling of strong coupled quantum matter physics can be achieved with strong performance.
Abstract: Hongtao Yan, Jin Mo Bok, Junfeng He1†, Wentao Zhang1‡, Qiang Gao, Xiangyu Luo, Yongqing Cai, Yingying Peng1§, Jianqiao Meng1¶, Cong Li, Hao Chen, Chunyao Song, Chaohui Yin, Taimin Miao, Genda Gu, Chengtian Lin, Fengfeng Zhang, Feng Yang, Shenjin Zhang, Qinjun Peng, Guodong Liu, Lin Zhao, Han-Yong Choi, Zuyan Xu and X. J. Zhou1,2,7,9,∗ National Lab for Superconductivity, Beijing National laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China University of Chinese Academy of Sciences, Beijing 100049, China Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea Condensed Matter Physics, Materials Science Division of Brookhaven National Laboratory, Upton, NY 11973-5000, USA Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China Department of Physics, Sungkyunkwan University, Suwon 16419, Korea Beijing Academy of Quantum Information Sciences, Beijing 100193, China †Present address: Department of Physics and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, University of Science and Technology of China, Hefei, Anhui 230026, China ‡Present address: Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
TL;DR: In this article , the authors reveal rich nodal loops in the existing material XSb (X = La, Pr, Nd) in the absence of spin-orbital coupling (SOC), which are enabled by symmetry.
TL;DR: In this article , the theoretical capacity of six flat boron sheets with different hexagonal hole densities was investigated, including adsorption, diffusion, theoretical capacity, and open-circuit voltage.
Abstract: Low-capacity anode materials have been limiting the further take-off of lithium-ion batteries (LIBs), and many researchers are relentlessly pursuing breakthroughs in high-capacity anode materials. Therefore, the properties of materials with a high theoretical capacity and the reasons behind them are worthy of further study. Here, based on the first-principles calculation, we systematically investigate the electrochemical properties of the six flat boron sheets with different hexagonal hole densities η (η = 1/4, 1/5, 1/6, 1/7, 1/8, 1/9), including adsorption, diffusion, theoretical capacity, and open-circuit voltage. We find that due to their own structural and electronic properties, the Li atoms tend to be adsorbed on their hexagonal hole sites, which result in the formation of structures of flat boron sheets with more hexagonal holes that have a higher theoretical capacity for lithium. Besides, their theoretical capacities can be calculated using the empirical equation, with the hexagonal hole densities (η). Finally, we obtain their capacities with increasing hexagonal hole density (η), which are 620, 708, 826, 992, 1240, and 1653 mA h g–1, respectively. Therefore, our results indicate that the porous structure of the anode material is beneficial to improve the storage capacity performance of LIBs.
TL;DR: In this paper , the photocatalytic properties of MoWS4 are investigated based on density functional theory (DFT), and the electron mobility of MoS4 monolayer is 557 cm2 V−1s−1, which is seven times higher than MoS2 monolayers.
Abstract: With the rising demand for renewable energy, photocatalysts are considered the most promising solution to harness solar energy, and the search for photocatalysts with excellent performances remains an urgent task. Here, based on density functional theory (DFT), the photocatalytic properties of MoWS4 are systematically investigated. The MoWS4 monolayer and bilayer are demonstrated as semiconductors with indirect band gaps of 2.01 and 1.48 eV. Moreover, they exhibit high and anisotropic light absorption coefficients of up to ∼105 cm−1 in the visible-ultraviolet region. The intrinsic band edge positions could fully satisfy the redox potentials of water without any external adjustment. The electron mobility of MoWS4 monolayer is 557 cm2 V−1s−1, which is seven times higher than MoS2 monolayer. Hence, MoWS4 can be regarded as a promising 2D photocatalyst candidate for water splitting.
TL;DR: In this paper , a topological semimetal Co3Sn2S2 with shandite structure was successfully synthesized experimentally by a green and environmentally friendly hydrothermal method.
Abstract: In the field of condensed matter physics, as new quantum materials, topological semimetals have a special topological energy band structure and nontrivial band crossings in the energy band, which will have many excellent topological properties, such as internal insulation of topological insulators and the presence of conduction electrons on the surface; this makes topological semimetals exhibit wider application prospects in electronic devices. So far, the experimental synthesis of topological semimetals was performed using physical methods to synthesize bulk single crystals, which is not conducive to the commercial application of micro and small devices. Weyl semimetal Co3Sn2S2 with shandite structure was successfully synthesized experimentally by a green and environmentally friendly hydrothermal method. Adjusting its reaction temperature, molar atomic ratio of elements and annealing temperature, and other experimental conditions, we analyze the crystal structure and physical properties of Co3Sn2S2, with the nanocrystal size being about 200 nm. We found that the Co3Sn2S2 synthesized by the hydrothermal method has a Curie temperature at 100 K to undergo ferromagnetic transition.
TL;DR: In this paper , the authors proposed AB2 (Cr, Mo, B = Si, Ge) compounds that feature a pair of triple points (TPs) on high-symmetry paths in the absence of spin-orbital coupling.
Abstract: Topological semimetals with nontrivial band crossing points have attracted widespread interest in recent years. Here, we propose that AB2 (A = Cr, Mo; B = Si, Ge) compounds are topological semimetals that feature a pair of triple points (TPs) on high-symmetry paths in the absence of spin-orbital coupling (SOC). In particular, the existence of this kind of TP is accompanied by a quadratic nodal line (QNL). In addition, we discover that these TPs are movable. Under a triaxial strain, we can change their positions on high-symmetry paths. When considering SOC, TPs transform into two pairs of type-II Dirac points along the high-symmetry path. Akin to TPs without SOC, each pair of Dirac points can also shift their positions on the high-symmetry paths under a triaxial strain. To characterize this property of TPs and Dirac points, we construct an effective model around the TPs and Dirac points, finding that there indeed exists a parameter that could characterize the movable properties for the TPs and Dirac points. According to the bulk-surface correspondence, we also discover that the length of the Fermi arcs that correspond to the nontrivial band crossings are also altered when changing their positions. Meanwhile, the shapes of Fermi arcs are also changed. Therefore, our work provides a platform to study the band crossings that are movable. The controllable fermions are beneficial to utilize the topological materials in nano-devices.
07 Dec 2022
TL;DR: Wu et al. as discussed by the authors proposed a method to solve the problem of particle motion in the context of condensed matter physics and showed that the method can be used to solve particle motion problems.
Abstract: Dingsong Wu1,2,†, Junjie Jia1,2,†, Jiangang Yang1,2,†, Wenshan Hong, Yingjie Shu, Taimin Miao, Hongtao Yan, Hongtao Rong, Ping Ai, Xing Zhang, Chaohui Yin, Chenlong Li, Shenjin Zhang, Fengfeng Zhang, Feng Yang, Zhimin Wang, Nan Zong, Lijuan Liu, Rukang Li, Xiaoyang Wang, Qinjun Peng, Hanqing Mao, Guodong Liu, Shiliang Li, Huiqian Luo, Xianxin Wu, Zuyan Xu, Lin Zhao1,2,5F and X. J. Zhou1,2,5F Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China. University of Chinese Academy of Sciences, Beijing 100049, China. Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China. Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.
12 Oct 2022
TL;DR: Zhou et al. as discussed by the authors proposed a method to solve the problem of superconductivity in the context of quantum information sciences, and showed that the method can be applied in the field of condensed matter physics.
Abstract: Xiangyu Luo1,3,†, Hao Chen1,3,†, Yinghao Li1,3,†, Qiang Gao, Chaohui Yin, Hongtao Yan, Taimin Miao, Hailan Luo, Yingjie Shu, Yiwen Chen, Chengtian Lin, Shenjin Zhang, Zhimin Wang, Fengfeng Zhang, Feng Yang, Qinjun Peng, Guodong Liu, Lin Zhao, Zuyan Xu, Tao Xiang and X. J. Zhou1,3,6,7,∗ National Lab for Superconductivity, Beijing National laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China Beijing National laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China University of Chinese Academy of Sciences, Beijing 100049, China Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China Beijing Academy of Quantum Information Sciences, Beijing 100193, China †These authors contributed equally to this work. ∗Corresponding author: XJZhou@iphy.ac.cn
TL;DR: In this paper , the authors perform a systematic search for ferromagnetic (FM) sextuple points (SPs) in the absence of spin-orbit coupling, and they find 5 SGs that could host SPs at high-symmetry points.
Abstract: The most fundamental symmetry in condensed matter physics is the crystallographic symmetry, such that solids could exhibit unconventional excitations beyond Dirac and Weyl fermions. Among the unconventional fermions, the sextuple excitation has been predicted in many nonmagnetic materials. However, the study of magnetic sextuple excitations has fallen behind because of the complicated magnetic structures of materials. Here we perform a systematic search for ferromagnetic (FM) sextuple points (SPs) in the absence of spin-orbit coupling. Based on 230 space groups (SGs), we find there are 5 SGs that could host SPs at high-symmetry points. Regarding the stability of the sextuple excitation, we reveal that the minimum little point group at where the SP locates is ${\mathrm{T}}_{d}$. To support this result, we construct the effective model based on the $k\ifmmode\cdot\else\textperiodcentered\fi{}p$ method, from which the linear dispersion can be read off. Via first-principles calculations, we also identify 67 FM material candidates, which realize the SPs with completely/incompletely spin polarized. To support our theory, we pick one of the FM materials, ${\mathrm{Rb}}_{4}{\mathrm{O}}_{6}$, as an example in which there is a fully spin-polarized SP. Finally, our work paves the way to study the spin-polarized SPs and provides a platform to realize the spintronic associated with sextuple excitations.
TL;DR: In this article , a laser-based angle-resolved photoemission measurement was performed on the Bi2Sr1.6La0.4CuO6+δ superconducting superconductor along the entire Fermi surface.
Abstract:
The pseudogap state is one of the most enigmatic characteristics in the anomalous normal state properties of the high temperature cuprate superconductors. A central issue is to reveal whether there is a symmetry breaking and which symmetries are broken across the pseudogap transition. By performing high resolution laser-based angle-resolved photoemission measurements on the optimally-doped Bi2Sr1.6La0.4CuO6+δ
superconductor, we report the observations of the particle-hole symmetry conservation in both the superconducting state and the pseudogap state along the entire Fermi surface. These results provide key insights in understanding the nature of the pseudogap and its relation with high temperature superconductivity.
TL;DR: In this paper , the defect-related properties of an AlN sample prepared based on the optimal process parameters by metal nitride vapor phase epitaxy (MNVPE) were investigated, and it was found that the fusion of a large number of a + c type dislocations occur at the interface of the low temperature buffer layer and the epitaxial layer, which affects the growth mode of the epitaxis.
Abstract: Herein, the defect-related properties of an AlN sample prepared based on the optimal process parameters by metal nitride vapor phase epitaxy (MNVPE) were investigated. The FWHM values of the (0002)/(101̅2) planes of the sample by MNVPE are 397/422 arcsec; the advantages of similar FWHM values of (0002) and (101̅2) planes will have a huge advantage over other preparation methods such as MOCVD. From the cross-sectional TEM images of the AlN sample, it is found that the fusion of a large number of a + c type dislocations occur at the interface of the low temperature buffer layer and the epitaxial layer, which affects the growth mode of the epitaxial layer. The lower FHWM value of the E2(high) peak of the Raman spectrum, the lower the point defect concentration, which made the sample gain higher energy defect emission bands in the PL spectra and higher transmittance in the UV–vis transmission spectrum.