Pub Date : 2024-04-30DOI: 10.1088/0256-307x/41/5/057403
Jie-Ran Xue, 洁然 薛, Fa Wang and 垡 王
The recent discovery of possible high temperature superconductivity in single crystals of La3Ni2O7 under pressure renews the interest in research on nickelates. The density functional theory calculations reveal that both dz2 and dx2–y2 orbitals are active, which suggests a minimal two-orbital model to capture the low-energy physics of this system. In this work, we study a bilayer two-orbital t–J model within multiband Gutzwiller approximation, and discuss the magnetism as well as the superconductivity over a wide range of the hole doping. Owing to the inter-orbital super-exchange process between dz2 and dx2–y2 orbitals, the induced ferromagnetic coupling within layers competes with the conventional antiferromagnetic coupling, and leads to complicated hole doping dependence for the magnetic properties in the system. With increasing hole doping, the system transfers to A-type antiferromagnetic state from the starting G-type antiferromagnetic (G-AFM) state. We also find the inter-layer superconducting pairing of dx2–y2 orbitals dominates due to the large hopping parameter of dz2 along the vertical inter-layer bonds and significant Hund’s coupling between dz2 and dx2–y2 orbitals. Meanwhile, the G-AFM state and superconductivity state can coexist in the low hole doping regime. To take account of the pressure, we also analyze the impacts of inter-layer hopping amplitude on the system properties.
{"title":"Magnetism and Superconductivity in the t–J Model of La3Ni2O7 Under Multiband Gutzwiller Approximation","authors":"Jie-Ran Xue, 洁然 薛, Fa Wang and 垡 王","doi":"10.1088/0256-307x/41/5/057403","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/057403","url":null,"abstract":"The recent discovery of possible high temperature superconductivity in single crystals of La3Ni2O7 under pressure renews the interest in research on nickelates. The density functional theory calculations reveal that both dz2 and dx2–y2 orbitals are active, which suggests a minimal two-orbital model to capture the low-energy physics of this system. In this work, we study a bilayer two-orbital t–J model within multiband Gutzwiller approximation, and discuss the magnetism as well as the superconductivity over a wide range of the hole doping. Owing to the inter-orbital super-exchange process between dz2 and dx2–y2 orbitals, the induced ferromagnetic coupling within layers competes with the conventional antiferromagnetic coupling, and leads to complicated hole doping dependence for the magnetic properties in the system. With increasing hole doping, the system transfers to A-type antiferromagnetic state from the starting G-type antiferromagnetic (G-AFM) state. We also find the inter-layer superconducting pairing of dx2–y2 orbitals dominates due to the large hopping parameter of dz2 along the vertical inter-layer bonds and significant Hund’s coupling between dz2 and dx2–y2 orbitals. Meanwhile, the G-AFM state and superconductivity state can coexist in the low hole doping regime. To take account of the pressure, we also analyze the impacts of inter-layer hopping amplitude on the system properties.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"22 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141062475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quantum anomalous Hall (QAH) insulators have highly potential applications in spintronic device. However, available candidates with tunable Chern numbers and high working temperature are quite rare. Here, we predict a 1T-PrN2 monolayer as a stable QAH insulator with high magnetic transition temperature of above 600 K and tunable high Chern numbers of C = ±3 from first-principles calculations. Without spin-orbit coupling (SOC), the 1T-PrN2 monolayer is predicted to be a p-state Dirac half metal with high Fermi velocity. Rich topological phases depending on magnetization directions can be found when the SOC is considered. The QAH effect with periodical changes of Chern number (±1) can be produced when the magnetic moment breaks all twofold rotational symmetries in the xy plane. The critical state can be identified as Weyl half semimetals. When the magnetization direction is parallel to the z-axis, the system exhibits high Chern number QAH effect with C = ±3. Our work provides a new material for exploring novel QAH effect and developing high-performance topological devices.
量子反常霍尔（QAH）绝缘体在自旋电子器件中具有极大的应用潜力。然而，具有可调切尔诺数和高工作温度的候选材料却非常罕见。在这里，我们通过第一性原理计算预测了 1T-PrN2 单层是一种稳定的 QAH 绝缘体，具有高于 600 K 的高磁场转变温度和 C = ±3 的可调高切尔数。在没有自旋轨道耦合（SOC）的情况下，1T-PrN2 单层被预测为具有高费米速度的 p 态狄拉克半金属。考虑到自旋轨道耦合（SOC）时，可以发现取决于磁化方向的丰富拓扑相。当磁矩打破 xy 平面上的所有二重旋转对称性时，就会产生切尔诺数周期性变化（±1）的 QAH 效应。临界状态可确定为韦尔半半金属。我们的工作为探索新型 QAH 效应和开发高性能拓扑器件提供了一种新材料。
{"title":"Quantum Anomalous Hall Effect with Tunable Chern Numbers in High-Temperature 1T-PrN2 Monolayer","authors":"Xu-Cai Wu, 绪才 吴, Shu-Zong Li, 树宗 李, Jun-Shan Si, 君山 司, Bo Huang, 博 黄, Wei-Bing Zhang and 卫兵 张","doi":"10.1088/0256-307x/41/5/057303","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/057303","url":null,"abstract":"Quantum anomalous Hall (QAH) insulators have highly potential applications in spintronic device. However, available candidates with tunable Chern numbers and high working temperature are quite rare. Here, we predict a 1T-PrN2 monolayer as a stable QAH insulator with high magnetic transition temperature of above 600 K and tunable high Chern numbers of C = ±3 from first-principles calculations. Without spin-orbit coupling (SOC), the 1T-PrN2 monolayer is predicted to be a p-state Dirac half metal with high Fermi velocity. Rich topological phases depending on magnetization directions can be found when the SOC is considered. The QAH effect with periodical changes of Chern number (±1) can be produced when the magnetic moment breaks all twofold rotational symmetries in the xy plane. The critical state can be identified as Weyl half semimetals. When the magnetization direction is parallel to the z-axis, the system exhibits high Chern number QAH effect with C = ±3. Our work provides a new material for exploring novel QAH effect and developing high-performance topological devices.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"12 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141152342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Research of Maxwell demon and quantum entanglement is important because of its foundational significance in physics and its potential applications in quantum information. Previous studies on the Maxwell demon have primarily focused on thermodynamics, taking into account quantum correlations. Here we consider from another perspective and ask whether quantum non-locality correlations can be simulated by performing work. The Maxwell demon-assisted Einstein–Podolsky–Rosen (EPR) steering is thus proposed, which implies a new type of loophole. The application of Landauer’s erasure principle suggests that the only way to close this loophole during a steering task is by continuously monitoring the heat fluctuation of the local environment by the participant. We construct a quantum circuit model of Maxwell demon-assisted EPR steering, which can be demonstrated by current programmable quantum processors, such as superconducting quantum computers. Based on this quantum circuit model, we obtain a quantitative formula describing the relationship between energy dissipation due to the work of the demon and quantum non-locality correlation. The result is of great physical interest because it provides a new way to explore and understand the relationship between quantum non-locality, information, and thermodynamics.
{"title":"Maxwell Demon and Einstein–Podolsky–Rosen Steering","authors":"Meng-Jun Hu, 孟军 胡, Xiao-Min Hu, 晓敏 胡, Yong-Sheng Zhang and 永生 张","doi":"10.1088/0256-307x/41/5/050302","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/050302","url":null,"abstract":"Research of Maxwell demon and quantum entanglement is important because of its foundational significance in physics and its potential applications in quantum information. Previous studies on the Maxwell demon have primarily focused on thermodynamics, taking into account quantum correlations. Here we consider from another perspective and ask whether quantum non-locality correlations can be simulated by performing work. The Maxwell demon-assisted Einstein–Podolsky–Rosen (EPR) steering is thus proposed, which implies a new type of loophole. The application of Landauer’s erasure principle suggests that the only way to close this loophole during a steering task is by continuously monitoring the heat fluctuation of the local environment by the participant. We construct a quantum circuit model of Maxwell demon-assisted EPR steering, which can be demonstrated by current programmable quantum processors, such as superconducting quantum computers. Based on this quantum circuit model, we obtain a quantitative formula describing the relationship between energy dissipation due to the work of the demon and quantum non-locality correlation. The result is of great physical interest because it provides a new way to explore and understand the relationship between quantum non-locality, information, and thermodynamics.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"34 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141152345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI3 and CrSe2 monolayers. It is found that the stacking order plays a crucial role in the interlayer magnetic coupling. Among all possible stacking structures, the AA-stacking is the most stable heterostructure, exhibiting interlayer antiferromagnetic interactions. Interestingly, the interlayer magnetic interaction can be effectively tuned by biaxial strain. A 4.3% compressive strain would result in a ferromagnetic interlayer interaction in all stacking orders. These results reveal the magnetic properties of CrI3/CrSe2 heterostructure, which is expected to be applied to spintronic devices.
{"title":"Interlayer Magnetic Interaction in the CrI3/CrSe2 Heterostructure","authors":"Qiu-Hao Wang, 秋皓 王, Mei-Yan Ni, 美燕 倪, Shu-Jing Li, 淑静 李, Fa-Wei Zheng, 法伟 郑, Hong-Yan Lu, 洪艳 路, Ping Zhang and 平 张","doi":"10.1088/0256-307x/41/5/057401","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/057401","url":null,"abstract":"Based on first-principles calculations, we systematically study the stacking energy and interlayer magnetic interaction of the heterobilayer composed of CrI3 and CrSe2 monolayers. It is found that the stacking order plays a crucial role in the interlayer magnetic coupling. Among all possible stacking structures, the AA-stacking is the most stable heterostructure, exhibiting interlayer antiferromagnetic interactions. Interestingly, the interlayer magnetic interaction can be effectively tuned by biaxial strain. A 4.3% compressive strain would result in a ferromagnetic interlayer interaction in all stacking orders. These results reveal the magnetic properties of CrI3/CrSe2 heterostructure, which is expected to be applied to spintronic devices.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"57 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140888498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-01DOI: 10.1088/0256-307x/41/3/031202
Jing Wu, Shanshan Cao, Feng Li
Jet quenching parameter q^ is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson model, we develop a new framework for calculating q^ at finite chemical potentials, in which q^ is related to the spectral function of the chiral order parameter. A mean field perturbative calculation up to the one-loop order indicates that the momentum broadening of jets is enhanced at both high temperature and high chemical potential, and approximately proportional to the parton number density in the partonic phase. We further investigate the behavior of q^ in the vicinity of the critical endpoint (CEP) by coupling our calculation with a recently developed equation of state that includes a CEP in the universality class of the Ising model, from which we discover the partonic critical opalescence, i.e., the divergence of scattering rate of jets and their momentum broadening at the CEP, contributed by scatterings via the σ exchange process. Hence, for the first time, jet quenching is connected with the search of CEP.
{"title":"Critical Opalescence and Its Impact on the Jet Quenching Parameter q^","authors":"Jing Wu, Shanshan Cao, Feng Li","doi":"10.1088/0256-307x/41/3/031202","DOIUrl":"https://doi.org/10.1088/0256-307x/41/3/031202","url":null,"abstract":"Jet quenching parameter <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson model, we develop a new framework for calculating <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> at finite chemical potentials, in which <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> is related to the spectral function of the chiral order parameter. A mean field perturbative calculation up to the one-loop order indicates that the momentum broadening of jets is enhanced at both high temperature and high chemical potential, and approximately proportional to the parton number density in the partonic phase. We further investigate the behavior of <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn6.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> in the vicinity of the critical endpoint (CEP) by coupling our calculation with a recently developed equation of state that includes a CEP in the universality class of the Ising model, from which we discover the partonic critical opalescence, i.e., the divergence of scattering rate of jets and their momentum broadening at the CEP, contributed by scatterings via the <italic toggle=\"yes\">σ</italic> exchange process. Hence, for the first time, jet quenching is connected with the search of CEP.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"26 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140568375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-01DOI: 10.1088/0256-307x/41/4/047103
Hai-Yang Ma, Jia-Xin Yin, M. Zahid Hasan, Jianpeng Liu
We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.
{"title":"Theory for Charge Density Wave and Orbital-Flux State in Antiferromagnetic Kagome Metal FeGe","authors":"Hai-Yang Ma, Jia-Xin Yin, M. Zahid Hasan, Jianpeng Liu","doi":"10.1088/0256-307x/41/4/047103","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047103","url":null,"abstract":"We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"232 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140615689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report a linear-scaling random Green’s function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H2O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H2O clusters at T = 0 K can reach an error of ∼ 1 meV per H2O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.
{"title":"Random Green’s Function Method for Large-Scale Electronic Structure Calculation","authors":"Mingfa Tang, Chang Liu, Aixia Zhang, Qingyun Zhang, Jiayu Zhai, Shengjun Yuan, Youqi Ke","doi":"10.1088/0256-307x/41/5/053102","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/053102","url":null,"abstract":"We report a linear-scaling random Green’s function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H<sub>2</sub>O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H<sub>2</sub>O clusters at <italic toggle=\"yes\">T</italic> = 0 K can reach an error of ∼ 1 meV per H<sub>2</sub>O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"9 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140929695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-01DOI: 10.1088/0256-307x/41/4/047101
R. Wang, Z. Song
A Moiré system is formed when two periodic structures have a slightly mismatched period, resulting in unusual strongly correlated states in the presence of particle-particle interactions. The periodic structures can arise from the intrinsic crystalline order and periodic external field. We investigate a one-dimensional Hubbard model with periodic on-site potential of period n0, which is commensurate to the lattice constant. For large n0, the exact solution demonstrates that there is a midgap flat band with zero energy in the absence of Hubbard interaction. Each Moiré unit cell contributes two zero energy levels to the flat band. In the presence of Hubbard interaction, the midgap physics is demonstrated to be well described by a uniform Hubbard chain in which the effective hopping and on-site interaction strength can be controlled by the amplitude and period of the external field. Numerical simulations are performed to demonstrate the correlated behaviors in the finite-sized Moiré Hubbard system, including the existence of an η-pairing state and bound pair oscillation. This finding provides a method to enhance the correlated effect by a spatially periodic external field.
{"title":"Flat Band and η-Pairing States in a One-Dimensional Moiré Hubbard Model","authors":"R. Wang, Z. Song","doi":"10.1088/0256-307x/41/4/047101","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047101","url":null,"abstract":"A Moiré system is formed when two periodic structures have a slightly mismatched period, resulting in unusual strongly correlated states in the presence of particle-particle interactions. The periodic structures can arise from the intrinsic crystalline order and periodic external field. We investigate a one-dimensional Hubbard model with periodic on-site potential of period <italic toggle=\"yes\">n</italic>\u0000<sub>0</sub>, which is commensurate to the lattice constant. For large <italic toggle=\"yes\">n</italic>\u0000<sub>0</sub>, the exact solution demonstrates that there is a midgap flat band with zero energy in the absence of Hubbard interaction. Each Moiré unit cell contributes two zero energy levels to the flat band. In the presence of Hubbard interaction, the midgap physics is demonstrated to be well described by a uniform Hubbard chain in which the effective hopping and on-site interaction strength can be controlled by the amplitude and period of the external field. Numerical simulations are performed to demonstrate the correlated behaviors in the finite-sized Moiré Hubbard system, including the existence of an <italic toggle=\"yes\">η</italic>-pairing state and bound pair oscillation. This finding provides a method to enhance the correlated effect by a spatially periodic external field.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"41 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140929541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-01DOI: 10.1088/0256-307x/41/3/037304
Danwen Yuan, Changming Yue, Yuefang Hu, Wei Zhang
The nontrivial band topologies protected by certain symmetries have attracted significant interest in condensed matter physics. The discoveries of nontrivial topological phases in real materials provide a series of archetype materials to further explore the topological physics. Ternary borides M2XB2 (M = W, Mo; X = Co, Ni) have been widely investigated as the wear-resistant and high-hardness materials. Based on first-principles calculations, we find the nontrivial topological properties in these materials. Taking W2NiB2 as an example, this material shows the nodal line semimetal state in the absence of spin-orbit coupling. Two types of nodal lines appear near the Fermi level simultaneously. One is protected by the combined space-inversion and time-reversal symmetry, and the other is by the mirror symmetry. Part of these two-type nodal lines form nodal chains. When spin-orbit coupling is included, these nodal lines are fully gapped and the system becomes a strong topological insulator with nontrivial Z2 index (1;000). Our calculations demonstrate that a nontrivial spin-momentum locked surface Dirac cone appears on the (1¯10) surface. We also find that other isostructural ternary borides Mo2NiB2, Mo2CoB2, and W2CoB2 possess similar topological band structures. Therefore, our work not only enriches the understanding of band topology for ternary borides, but also lays the foundation for the further study of topological phases manipulation and potential spintronic applications in realistic materials.
{"title":"Nontrivial Topological Phases in Ternary Borides M2XB2 (M=W, Mo; X=Co, Ni)","authors":"Danwen Yuan, Changming Yue, Yuefang Hu, Wei Zhang","doi":"10.1088/0256-307x/41/3/037304","DOIUrl":"https://doi.org/10.1088/0256-307x/41/3/037304","url":null,"abstract":"The nontrivial band topologies protected by certain symmetries have attracted significant interest in condensed matter physics. The discoveries of nontrivial topological phases in real materials provide a series of archetype materials to further explore the topological physics. Ternary borides M<sub>2</sub>XB<sub>2</sub> (M = W, Mo; X = Co, Ni) have been widely investigated as the wear-resistant and high-hardness materials. Based on first-principles calculations, we find the nontrivial topological properties in these materials. Taking W<sub>2</sub>NiB<sub>2</sub> as an example, this material shows the nodal line semimetal state in the absence of spin-orbit coupling. Two types of nodal lines appear near the Fermi level simultaneously. One is protected by the combined space-inversion and time-reversal symmetry, and the other is by the mirror symmetry. Part of these two-type nodal lines form nodal chains. When spin-orbit coupling is included, these nodal lines are fully gapped and the system becomes a strong topological insulator with nontrivial <italic toggle=\"yes\">Z</italic>\u0000<sub>2</sub> index (1;000). Our calculations demonstrate that a nontrivial spin-momentum locked surface Dirac cone appears on the <inline-formula>\u0000<tex-math>\u0000<?CDATA $(bar{1}10)$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mo stretchy=\"false\">(</mml:mo><mml:mover accent=\"true\"><mml:mn>1</mml:mn><mml:mo stretchy=\"true\">¯</mml:mo></mml:mover><mml:mn>10</mml:mn><mml:mo stretchy=\"false\">)</mml:mo></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_037304_ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> surface. We also find that other isostructural ternary borides Mo<sub>2</sub>NiB<sub>2</sub>, Mo<sub>2</sub>CoB<sub>2</sub>, and W<sub>2</sub>CoB<sub>2</sub> possess similar topological band structures. Therefore, our work not only enriches the understanding of band topology for ternary borides, but also lays the foundation for the further study of topological phases manipulation and potential spintronic applications in realistic materials.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"12 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-01DOI: 10.1088/0256-307x/41/3/031201
Xiao-Yun Wang, Chen Dong, Xiang Liu
We investigate the nature of the strong coupling constant and related physics. Through the analysis of accumulated experimental data around the world, we employ the ability of machine learning to unravel its physical laws. The result of our efforts is a formula that captures the expansive panorama of the distribution of the strong coupling constant across the entire energy range. Importantly, this newly derived expression is very similar to the formula derived from the Dyson–Schwinger equations based on the framework of Yang–Mills theory. By introducing the Euler number e into the functional formula of the strong coupling constant at high energies, we successfully solve the puzzle of the infrared divergence, which allows for a seamless transition of the strong coupling constant from the perturbative to the non-perturbative energy regime. Moreover, the obtained ghost and gluon dressing function distribution results confirm that the obtained strong coupling constant formula can well describe the physical properties of the non-perturbed regime. In addition, we study the quantum-chromodynamics strong coupling constant result of the Bjorken sum rule Γ1p−n and the quark–quark static energy E0(r), and find that the global energy scale can effectively interpret the experimental data. The present results shed light on the puzzling properties of quantum chromodynamics and the intricate interplay of strong coupling constants at both low and high energy scales.
{"title":"Analysis of Strong Coupling Constant with Machine Learning and Its Application","authors":"Xiao-Yun Wang, Chen Dong, Xiang Liu","doi":"10.1088/0256-307x/41/3/031201","DOIUrl":"https://doi.org/10.1088/0256-307x/41/3/031201","url":null,"abstract":"We investigate the nature of the strong coupling constant and related physics. Through the analysis of accumulated experimental data around the world, we employ the ability of machine learning to unravel its physical laws. The result of our efforts is a formula that captures the expansive panorama of the distribution of the strong coupling constant across the entire energy range. Importantly, this newly derived expression is very similar to the formula derived from the Dyson–Schwinger equations based on the framework of Yang–Mills theory. By introducing the Euler number <italic toggle=\"yes\">e</italic> into the functional formula of the strong coupling constant at high energies, we successfully solve the puzzle of the infrared divergence, which allows for a seamless transition of the strong coupling constant from the perturbative to the non-perturbative energy regime. Moreover, the obtained ghost and gluon dressing function distribution results confirm that the obtained strong coupling constant formula can well describe the physical properties of the non-perturbed regime. In addition, we study the quantum-chromodynamics strong coupling constant result of the Bjorken sum rule <inline-formula>\u0000<tex-math>\u0000<?CDATA ${varGamma }_{1}^{p-n}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>Γ</mml:mi><mml:mn>1</mml:mn><mml:mrow><mml:mi>p</mml:mi><mml:mo>−</mml:mo><mml:mi>n</mml:mi></mml:mrow></mml:msubsup></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031201_ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> and the quark–quark static energy <italic toggle=\"yes\">E</italic>\u0000<sub>0</sub>(<italic toggle=\"yes\">r</italic>), and find that the global energy scale can effectively interpret the experimental data. The present results shed light on the puzzling properties of quantum chromodynamics and the intricate interplay of strong coupling constants at both low and high energy scales.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":"22 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140311037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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