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Spin current Kondo effect in frustrated Kondo systems

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Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 91-98页

作者： Jiangfan Wang yi-feng yang Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

Magnetic frustrations can enhance quantum fluctuations in spin systems and lead to exotic topological insulating *** coupled to mobile electrons,they may give rise to unusual non-Fermi liquid or metallic spin liquid states whose nature has not been well ***,we propose a spin current Kondo mechanism underlying a series of non-Fermi liquid phases on the border of Kondo and magnetic phases in a frustrated three-impurity Kondo *** mechanism is confirmed by renormalization group analysis and describes movable Kondo singlets called"holons"induced by an effective coupling between the spin current of conduction electrons and the vector chirality of localized *** mechanisms may widely exist in all frustrated Kondo systems and be detected through spin current noise measurements.

关键词： Kondo effect spin current Kondo effect spin chirality magnetic frustration

A unified theory of ferromagnetic quantum phase transitions in heavy fermion metals

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Science China(Physics,Mechanics & Astronomy) 2022年第5期65卷 104-113页

作者： Jiangfan Wang yi-feng yang Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of ScienceBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

Motivated by the recent discovery of a continuous ferromagnetic quantum phase transition in Ce Rh_(6)Ge_(4) and its distinction from other U-based heavy fermion metals such as UGe_(2),we develop a unified explanation of their different ground state properties based on an anisotropic ferromagnetic Kondo-Heisenberg *** employ an improved large-N Schwinger boson approach and predict a full phase diagram containing both a continuous ferromagnetic quantum phase transition for large magnetic anisotropy and first-order transitions for relatively small *** calculations reveal three different ferromagnetic phases including a half-metallic spin selective Kondo insulator with a constant *** Fermi surface topologies are found to change abruptly between different phases,consistent with that observed in UGe_(2).At finite temperatures,we predict the development of Kondo hybridization well above the ferromagnetic long-range order and its relocalization near the phase transition,in good agreement with band measurements in Ce Rh_(6)Ge_(4).Our results highlight the importance of magnetic anisotropy and provide a unified theory for understanding the ferromagnetic quantum phase transitions in heavy fermion metals.

关键词： ferromagnetic Kondo lattice magnetic anisotropy ferromagnetic quantum phase transition Schwinger boson

Heavy fermion quantum criticality: The party is just beginning

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Science China(Physics,Mechanics & Astronomy) 2020年第11期63卷 129-130页

作者： yi-feng yang Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Songshan Lake Materials Laboratory Dongguan 523808China

Recently,Nature reported the discovery of a ferromagnetic quantum critical point(FM QCP)in the heavy fermion compound CeRh6Ge4[1].This is the first discovery of such kind in a stoichiometric *** FM order is suppressed at a critical pressure of 0.8 GPa,beyond which the ground state turns into a Fermi ***,Science had also reported the observation of a FM QCP,albeit in the doped compound YbNi4(P0.92As0.08)2[2].

关键词： compound. quantum compound

Influence of adding carbon nanotubes and graphite to Ag-MoS_2 composites on the electrical sliding wear properties

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Acta Metallurgica Sinica(English Letters) 2010年第1期23卷 27-34页

作者： Shu LI yi feng Xiting yang ~ v Department of Material Science and Engineering Hefei University of Technology Hefei 230009 China

Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.

关键词： Ag-MoS2 composite Carbon nanotube Graphite Contact voltage drop Friction coefficient Wear loss

Dynamic prediction of moving trajectory in pipe jacking: GRU-based deep learning framework

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Frontiers of Structural and Civil Engineering 2023年第7期17卷 994-1010页

作者： yi-feng yang Shao-Ming LIAO Meng-Bo LIU Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of Road and Traffic Engineering of Ministry of Education Tongji UniversityShanghai 201804China

The moving trajectory of the pipe-jacking machine(PJM),which primarily determines the end quality of jacked tunnels,must be controlled strictly during the entire jacking *** prediction models to support drivers in performing rectifications in advance can effectively avoid considerable trajectory deviations from the designed jacking ***,a gated recurrent unit(GRU)-based deep learning framework is proposed herein to dynamically predict the moving trajectory of the *** this framework,operational data are first extracted from a data acquisition system;subsequently,they are preprocessed and used to establish GRU-based multivariate multistep-ahead direct prediction *** verify the performance of the proposed framework,a case study of a large pipe-jacking project in Shanghai and comparisons with other conventional models(i.e.,long short-term memory(LSTM)network and recurrent neural network(RNN))are *** addition,the effects of the activation function and input time-step length on the prediction performance of the proposed framework are investigated and *** results show that the proposed framework can dynamically and precisely predict the PJM moving trajectory during the pipe-jacking process,with a minimum mean absolute error and root mean squared error(RMSE)of 0.1904 and 0.5011 mm,*** RMSE of the GRU-based models is lower than those of the LSTM-and RNN-based models by 21.46%and 46.40%at the maximum,*** proposed framework is expected to provide an effective decision support for moving trajectory control and serve as a foundation for the application of deep learning in the automatic control of pipe jacking.

关键词： dynamic prediction moving trajectory pipe jacking GRU deep learning

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Spectroscopic data de-noising via training-set-free deep learning method

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Science China(Physics,Mechanics & Astronomy) 2023年第6期66卷 191-199页

作者： Dongchen Huang Junde Liu Tian Qian yi-feng yang Beijing National Laboratoryfor Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

De-noising plays a crucial role in the post-processing of *** learning-based methods show good performance in extracting intrinsic information from noisy data,but often require a high-quality training set that is typically inaccessible in real experimental ***,using spectra in angle-resolved photoemission spectroscopy(ARPES)as an example,we develop a de-noising method for extracting intrinsic spectral information without the need for a training *** is possible as our method leverages the self-correlation information of the spectra *** preserves the intrinsic energy band features and thus facilitates further analysis and ***,since our method is not limited by specific properties of the training set compared with previous ones,it may well be extended to other fields and application scenarios where obtaining high-quality multidimensional training data is challenging.

关键词： de-noising deep learning spectroscopic data

Possible nodeless s~±-wave superconductivity in twisted bilayer graphene

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Chinese Physics B 2019年第7期28卷 91-97页

作者： Zhe Liu Yu Li yi-feng yang Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences. Beijing 100049 China Songshan Lake Materials Laboratory Dongguan 523808 China Collaborative Innovation Center of Quantum Matter Beijing 100190 China

The recent discovery of superconductivity in the twisted bilayer graphene has stimulated numerous theoretical proposals concerning its exact gap *** them, the d + id or p + ip-wave was believed to be the most plausible ***, considering that the superconductivity emerges near a correlated insulating state and may be induced by antiferromagnetic spin fluctuations, we apply the strong-coupling Eliashberg theory with both inter-and intraband quantum critical pairing interactions and discuss the possible gap symmetry in an effective low-energy four-orbital *** calculations reveal a nodeless s~±-wave as the most probable candidate for the superconducting gap symmetry in the experimentally relevant parameter *** solution is distinctly different from previous theoretical *** highlights the multi-gap nature of the superconductivity and puts the twisted bilayer graphene in the same class as the iron-pnictide,electron-doped cuprate, and some heavy fermion superconductors.

关键词： twisted bilayer graphene superconductivity

Impurity-induced bound states as a signature of pairing symmetry in multiband superconducting CeCu2Si2

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Frontiers of physics 2019年第1期14卷 99-104页

作者： Dong-Dong Wang Bin Liu Min Liu yi-feng yang Shi-Ping feng Department of Physics Beijing Jiaotong University Beijing 100044 China Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China Collaborative Innovation Center of Quantum Matter Beijing 100190 China Department of Physics Beijing Normal University Beijing 100875 China

The notion of multiband superconductivity with dominant two-gap features has been recently applied to the unconventional superconductor CeCu2Si2 for challenging the previously accepted concept of nodal d-wave pairing. In the proposed study, the realistic multiband Fermi surface topology of CeCu2Si2 was obtained through first-principles calculations, and analysis was conducted with an effective two-band hybridization model including detailed band structure. Within the T-matrix approximation, the obtained calculation results show that different pairing candidates, including fully gapped s-wave, loop-nodal s-wave, and d-wave pairings, could yield qualitatively distinct features characterized by impurity-induced bound states. These features can be verified through high-resolution scanning tunneling microscopy or spectroscopy and provide corroborative justification that would be beneficial for the ongoing research regarding the superconducting gap symmetry of CeCu2Si2 at ambient pressure.

关键词： heavy-fermion superconductivity pairing symmetry impurity effect local density of states

Evolution of Topological End States in the One-Dimensional Kondo–Heisenberg Model with Site Modulation

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Chinese Physics Letters 2022年第11期39卷 53-56页

作者： Neng Xie Danqing Hu Shu Chen yi-feng yang Beijing National Laboratory for Condensed Matter Physics and Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

We investigate interplay of topological and Kondo effects in a one-dimensional Kondo-Heisenberg model with nontrivial conduction band using the density matrix renormalization group *** analyzing the density profile,the local hybridization,and the spin/charge gap,we find that the Kondo effect can be destructed at edges of the chain by the topological end state below a finite critical Kondo coupling J_(K)^(C).We construct a phase diagram characterizing the transition of the end states.

关键词： method Kondo Heisenberg