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Manipulating Hubbard-type Coulomb blockade effect of metallic wires embedded in an insulator

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National Science Review 2023年第3期10卷 127-133页

作者： Xing Yang Zhao-Long Gu Huimin Wang Jing-Jing Xian Sheng Meng Naoto Nagaosa Wen-Hao Zhang Hai-Wen Liu Zi-Heng Ling Kai Fan Zhi-Mo Zhang Le Qin Zhi-Hao Zhang Yan Liang Jian-Xin Li Ying-Shuang Fu School of Physics and Wuhan National High Magnetic Field Center Huazhong University of Science and Technology National Laboratory of Solid State Microstructures and Department of Physics Nanjing University Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences RIKEN Center for Emergent Matter Science(CEMS) Department of Applied Physics University of Tokyo Center for Advanced Quantum Studies Department of Physics Beijing Normal University Collaborative Innovation Center of Advanced Microstructures Nanjing University Hubei Key Laboratory of Gravitation and Quantum Physics Huazhong University of Science and Technology Wuhan Institute of Quantum Technology

Correlated states have emerged in low-dimensional systems owing to enhanced Coulomb interactions.Elucidating these states requires atomic-scale characterization and delicate control capabilities.Herein,spectroscopic imaging-scanning tunneling microscopy was employed to investigate the correlated states residing in 1D electrons of the monolayer and bilayer MoSe2 mirror twin boundary(MTB).The Coulomb energies,determined by the wire length,drive the MTB into two types of ground states with distinct respective out-of-phase and in-phase charge orders.The two ground states can be reversibly converted through a metastable zero-energy state with in situ voltage pulses,which tune the electron filling of the MTB via a polaronic process,substantiated by first-principles calculations.Our Hubbard model calculation with an exact diagonalization method reveals the ground states as correlated insulators from an on-site U-originated Coulomb interaction,dubbed the Hubbard-type Coulomb blockade effect.Our study lays a foundation for understanding and tailoring correlated physics in complex systems.

关键词： STM one-dimensional Coulomb effect electron correlation Hubbard

Dynamical t/U Expansion of the Doped Hubbard Model

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Chinese Physics Letters 2024年第3期41卷 73-82页

作者：丁文新俞榕 School of Physics and Material Science Anhui UniversityHefei 230601China Kavli Institute for Theoretical Sciences University of Chinese Academy of SciencesBeijing 100190China Physics Department and Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices Renmin UniversityBeijing 100872China

We construct a new U(1)slave-spin representation for the single-band Hubbard model in the large-U limit.The mean-field theory in this representation is more amenable to describe both the spin-charge-separation physics... 详细信息

关键词： Hubbard representation separation

Phase Diagram of the BCS–Hubbard Model in a Magnetic Field

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Chinese Physics Letters 2022年第6期39卷 24-28页

作者： Dong-Hong Xu Yi-Cong Yu Xing-Jie Han Xi Chen Kang Wang Ming-Pu Qin Hai-Jun Liao Tao Xiang Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Wuhan Institute of Physics and Mathematics IAPMSTChinese Academy of SciencesWuhan 430071China School of Science Beijing University of Posts and TelecommunicationsBeijing 100876China Key Laboratory of Artificial Structures and Quantum Control School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Songshan Lake Materials Laboratory Dongguan 523808China Beijing Academy of Quantum Information Sciences Beijing 100193China

We propose an extended BCS–Hubbard model and investigate its ground state phase diagram in an external magnetic field.By mapping the model onto a model of spinless fermions coupled with conserving Z_(2) variables which are mimicked by pseudospins,the model is shown to be exactly solvable along the symmetric lines for an arbitrary on-site Hubbard interaction on the bipartite lattice.In the zero field limit,the ground states exhibit an antiferromagnetic order of pseudospins.In the large field limit,on the other hand,the pseudospins are fully polarized ordered.With the increase of the applied field,a first-order phase transition occurs between these kinds of phases when the on-site Coulomb interaction is less than a critical value U(c).Above this critical U_(c),a novel intermediate phase emerges between the fully polarized and antiferromagnetic phases.The ground states in this phase are macroscopically degenerate,like in a spin ice,and the corresponding entropy scales linearly with the lattice size at zero temperature.

关键词： temperature field Hubbard

Machine learning the Hubbard U parameter in DFT+U using Bayesian optimization

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npj Computational Materials 2020年第1期6卷 163-168页

作者： Maituo Yu Shuyang Yang Chunzhi Wu Noa Marom Department of Materials Science and Engineering Carnegie Mellon UniversityPittsburghPA 15213USA Department of Physics Carnegie Mellon UniversityPittsburghPA 15213USA Department of Chemistry Carnegie Mellon UniversityPittsburghPA 15213USA

Within density functional theory(DFT),adding a Hubbard U correction can mitigate some of the deficiencies of local and semi-local exchange-correlation functionals,while maintaining computational efficiency.However,the accuracy of DFT+U largely depends on the chosen Hubbard U values.We propose an approach to determining the optimal U parameters for a given material by machine learning.The Bayesian optimization(BO)algorithm is used with an objective function formulated to reproduce the band structures produced by more accurate hybrid functionals.This approach is demonstrated for transition metal oxides,europium chalcogenides,and narrow-gap semiconductors.The band structures obtained using the BO U values are in agreement with hybrid functional results.Additionally,comparison to the linear response(LR)approach to determining U demonstrates that the BO method is superior.

关键词： optimization Hubbard parameter

Hubbard U through polaronic defect states

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npj Computational Materials 2022年第1期8卷 2504-2511页

作者： Stefano Falletta Alfredo Pasquarello Chaire de Simulationàl’Echelle Atomique(CSEA) Ecole Polytechnique Fédérale de Lausanne(EPFL)CH-1015LausanneSwitzerland

Since the preliminary work of Anisimov and co-workers,the Hubbard corrected DFT+U functional has been used for predicting properties of correlated materials by applying on-site effective Coulomb interactions to specific orbitals.However,the determination of the Hubbard U parameter has remained under intense discussion despite the multitude of approaches proposed.Here,we define a selection criterion based on the use of polaronic defect states for the enforcement of the piecewise linearity of the total energy upon electron occupation.A good agreement with results from piecewise linear hybrid functionals is found for the electronic and structural properties of polarons,including the formation energies.The values of U determined in this way are found to give a robust description of the polaron energetics upon variation of the considered state.In particular,we also address a polaron hopping pathway,finding that the determined value of U leads to accurate energetics without requiring a configurational-dependent U.It is emphasized that the selection of U should be based on physical properties directly associated with the orbitals to which U is applied,rather than on more global properties such as band gaps and band widths.For comparison,we also determine U through a well-established linear-response scheme finding noticeably different values of U and consequently different formation energies.Possible origins of these discrepancies are discussed.As case studies,we consider the self-trapped electron in BiVO_(4),the self-trapped hole in MgO,the Li-trapped hole in MgO,and the Al-trapped hole inα-SiO_(2).

关键词： Hubbard polaron piecewise

A Possible Quantum Spin Liquid Phase in the Kitaev–Hubbard Model

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Chinese Physics Letters 2023年第12期40卷 109-113页

作者： Shaojun Dong Hao Zhang Chao Wang Meng Zhang Yong-Jian Han Lixin He Institute of Artificial Intelligence Hefei Comprehensive National Science CenterHefei 230088China CAS Key Laboratory of Quantum Information University of Science and Technology of ChinaHefei 230026China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of ChinaHefei 230026China Hefei National Laboratory University of Science and Technology of ChinaHefei 230088China

The quantum spin liquid(QSL) state of Kitaev-like materials, such as iridium oxides A_(2)IrO_(3) and α-RuCl_(3),has been explored in depth. The half-filled Kitaev–Hubbard model with bond-dependent hopping terms is used to describe the Kitaev-like materials, which is calculated using the state-of-the-art fermionic projected entangled pair states method. We find a QSL phase near the Mott insulator transition, which has a strong first-order transition to the semi-metal phase with the decrease of Hubbard U. We suggest that a promising approach to finding QSL states is by finding iridium oxides that are near the Mott insulator transition.

关键词： transition method Hubbard

Optoelectronic Properties of Pure and Co Doped Indium Oxide by Hubbard and modified Becke–Johnson Exchange Potentials

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Chinese Physics Letters 2013年第12期30卷 107-111页

作者： H.A.Rahnamaye Aliabad M.Bazrafshan H.Vaezi Masood Yousaf Junaid Munir M.A.Saeed Department of Physics Hakim Sabzevari UniversitySabzevarIran Department of Physics Khayyam Institute of Higher EducationMashhadIran Department of Physics Universiti Teknologi MalaysiaSkudai 81310JohorMalaysia

Structural and optoelectronic properties of pure and Co doped In2O3 are studied by employing the full-potential linearized augmented plane wave method,which is known to produce highly accurate results.First principles calculations are performed with ordinary generalized gradient approximation(GGA)along with new Hubbard and modified Becke-Johnson exchange(mBJ)potential techniques.Improved band gap results are obtained for In2O3 with GGA+U and mBJ.In the case of mBJ,the band gap values are 3.5 eV and 3.4 eV for rhombohedral and cubic phases,which are in close agreement with the experimental data.Substitution of In by Co 25%alters the energy gap and a spin splitting effect is observed in these phases.For the spin-up state,it remains semiconductor,whereas for the spin-down state it shows semimetallic behavior.The value of static refractive index n(0)is 1.74 for the cubic phase,while in rhombohedral phase the values of n(0)are 1.77 and 1.74 along xx and zz optical axes,respectively.The calculated optical properties conform anisotropy in the rhombohedral phase and these materials can be potential candidates for the optoelectronics applications.

关键词： behavior Hubbard cubic

Ground State Property of a One-Dimensional Bose–Hubbard Model Using Time-Evolving Body Decimation

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Chinese Physics Letters 2013年第8期30卷 125-128页

作者：欧阳生德刘竞向少华宋克慧 Department of Physics and Information Engineering Huaihua UniversityHuaihua 418000 Department of Education Science Huaihua UniversityHuaihua 418000

We study the ground state property of the one-dimensional Bose–Hubbard model using an imaginary time evolving body decimation algorithm.The single-particle density matrix is numerically calculated for a Mott insulating system and a superfluid system separately.By plotting the chemical potential versus the filling n=N/L for U/J=20 and U/J=0.1,we identify the Mott gap for U/J=20 in filling n=1.Lastly,we investigate the occupation number of the Bloch state with quasimomentum for a system deep in the Mott phase and in the superfluid phase respectively.The results indicate Bose condensation in the quasimomentum space.

关键词： space Hubbard system

Hubbard model on an anisotropic checkerboard lattice at finite temperatures: Magnetic and metal–insulator transitions

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Chinese Physics B 2019年第10期28卷 498-503页

作者：刘海迪 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of Sciences

We study magnetic and Mott transitions of the Hubbard model on the geometrically frustrated anisotropic checkerboard lattice at half filling using cellular dynamical mean-field theory. Phase diagrams over a wide area of the parameter space are obtained by varying the interparticle interaction strength, geometric frustration strength, and temperature. Our results show that frustration and thermal fluctuations play a competing role against the interactions and in general favor a metallic phase without antiferromagnetic order. Due to their interplay, the system exhibits competition between antiferromagnetic insulator, antiferromagnetic metal, paramagnetic insulator, and paramagnetic metal phases in the intermediateinteraction regime. In the strong-interaction limit, which reduces to the Heisenberg model, our result is consistent with previous studies.

关键词： geometrical frustration checkerboard lattice Hubbard model