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An experimental setup with controllable tuning parameters for studying the Kondo systems

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Science China(Physics,Mechanics & Astronomy) 2022年第4期65卷 121-122页

作者： zhong-yi lu Department of Physics Renmin University of ChinaBeijing 100872China

The Kondo physics has been studied since the 1960 s in condensed matter physics[1,2],which is mainly determined by two competing factors namely the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida(RKKY)interaction.

关键词： interaction Kondo condensed

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Three-dimensional acetylenic modified graphene for highperformance optoelectronics and topological materials

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npj Computational Materials 2021年第1期7卷 992-998页

作者： Yan Gao Chengyong zhong Shengyuan A.Yang Kai Liu zhong-yi lu Department of physics and Beijing Key Laboratory of Opto-electronic Functional Materials&Micro-nano Devices Renmin University of ChinaBeijingChina Institute for Advanced Study Chengdu UniversityChengduChina Research Laboratory for Quantum Materials Singapore University of Technology and DesignSingaporeSingapore Center for Quantum Transport and Thermal Energy Science School of Physics and TechnologyNanjing Normal UniversityNanjingChina

Seeking carbon phases with versatile properties is one of the fundamental goals in physics,chemistry,and materials ***,based on the first-principles calculations,a family of three-dimensional(3D)graphene networks with abundant and fabulous electronic properties,including rarely reported dipole-allowed truly direct band gap semiconductors with suitable band gaps(1.07–1.87 eV)as optoelectronic/photovoltaic materials and topological nodal-ring semimetals,are proposed through stitching different graphene layers with acetylenic ***,the optical absorption coefficients in some of those semiconducting carbon allotropes express possibly the highest performance among all of the semiconducting carbon phases known to *** the other hand,the topological states in those topological nodal-ring semimetals are protected by the time-reversal and spatial symmetry and present nodal rings and nodal helical loops topological *** newly revealed carbon phases possess low formation energies and excellent thermodynamic stabilities;thus,they not only host a great potential in the application of optoelectronics,photovoltaics,and quantum topological materials etc.,but also can be utilized as catalysis,molecule sieves or Liion anode materials and so ***,the approach used here to design novel carbon allotropes may also give more enlightenments to create various carbon phases with different applications.

关键词： dimensional topological versatile

Interaction-Induced Characteristic Length in Strongly Many-Body Localized Systems

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Chinese Physics Letters 2018年第2期35卷 75-79页

作者： Rong-Qiang He zhong-yi lu Department of Physics Renmin University of ChinaBeijing 100872 Institute for Advanced Study Tsinghua UniversityBeijing 100084

A complete set of local integrals of motion(LIOM)is a key concept for describing many-body localization(MBL),which explains a variety of intriguing phenomena in MBL *** example,LIOM constrain the dynamics and result in ergodicity violation and breakdown of the eigenstate thermalization ***,it is difficult to find a complete set of LIOM explicitly and accurately in practice,which impedes some quantitative structural characterizations of MBL *** we propose an accurate numerical method for constructing LIOM,discover through the LIOM an interaction-induced characteristic length+,and prove a'quasi-productstate'structure of the eigenstates with that characteristic length+for MBL *** specifically,we find that there are two characteristic lengths in the *** first one is governed by disorder and is of Andersonlocalization *** second one is induced by interaction but shows a discontinuity at zero interaction,showing a nonperturbative *** prove that the entanglement and correlation in any eigenstate extend not longer than twice the second length and thus the eigenstates of the system are the quasi-product states with such a localization length.

关键词： Numerical methods

Quantum anomalous hall effect in collinear antiferromagnetism

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npj Computational Materials 2023年第1期9卷 1655-1660页

作者： Peng-Jie Guo Zheng-Xin Liu zhong-yi lu Department of physics and Beijing Key Laboratory of Opto-electronic Functional Materials&Micro-nano Devices Renmin University of China100872 BeijingChina

The two-dimensional Quantum Hall effect with no external magnetic field is called the Quantum anomalous Hall (QAH) effect. Sofar, experimentally realized QAH insulators all exhibit ferromagnetic order and the QAH effect only occurs at very low *** the other hand, up to now the QAH effect in collinear antiferromagnetic (AFM) materials has never been reported and thecorresponding mechanism has never been proposed. In this work, we realize the QAH effect by proposing a four-band lattice modelwith static AFM order, which indicates that the QAH effect can be found in AFM materials. Then, as a prototype, we demonstratethat a monolayer CrO can be switched from an AFM Weyl semimetal to an AFM QAH insulator by applying strain, based onsymmetry analysis and the first-principles electronic structure calculations. Our work not only proposes a scenario to search for QAHinsulators in materials, but also reveals a way to considerably increase the critical temperature of the QAH phase.

关键词： materials effect effect

The melilite-type compound (Sr_(1-x),A_x)_2MnGe_2S_6O(A=K,La) being a room temperature ferromagnetic semiconductor

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Science Bulletin 2018年第14期63卷 887-891页

作者： Huan-Cheng Yang Ben-Chao Gong Kai Liu zhong-yi lu Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices Renmin University of China Beijing 100872 China

The seeking of room temperature ferromagnetic semiconductors, which take advantages of both the charge and spin degrees of freedom of electrons to realize a variety of functionalities in devices integrated with electronic, optical, and magnetic storage properties, has been a long-term goal of scientists and engi- neers. Here, by using the spin-polarized density functional theory calculations, we predict a new series of high temperature ferromagnetic semiconductors based on the melilite-type oxysulfide Sr2MnGe2S60 through hole （K） and electron （La） doping. Due to the lack of strong antiferromagnetic superexchange between Mn ions, the weak antiferromagnetic order in the parent compound Sr2MnGe2S60 can be sup- pressed easily by charge doping with either p-type magnetic order. At a doping concentration of or n-type carriers, giving rise to the expected ferro- 25%, both the hole-doped and electron-doped compounds can achieve a Curie temperature （To） above 300 K. The underlying mechanism is analyzed. Our study provides an effective approach for exploring new types of high temperature ferromagnetic semiconductors.

关键词： Ferromagnetic semiconductor Melilite Density functional theory calculations Hole doping Electron doping

An Anderson Impurity Interacting with the Helical Edge States in a Quantum Spin Hall Insulator

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Chinese Physics Letters 2018年第6期35卷 70-74页

作者： Ru Zheng Rong-Qiang He zhong-yi lu Department of Physics Renmin University of China

Using the natural orbitals renormalization group（NORG）method,we investigate the screening of the local spin of an Anderson impurity interacting with the helical edge states in a quantum spin Hall *** is found that there is a local spin formed at the impurity site and the local spin is completel.y screened by electrons in the quantum spin Hall ***,the local spin is screened dominantly by a single active natural *** then show that the Kondo screening mechanism becomes transparent and simple in the framework of the natural orbitals *** project the active natural orbital respectively into real space and momentum space to characterize its *** conilrm the spin-momentum locking property of the edge states based on the occupancy of a Bloch state on the edge to which the impurity ***,we study the dynamical property of the active natural orbital represented by the local density of states,from which we observe the Kondo resonance peak.

关键词： An Anderson Impurity Interacting with the Helical Edge States in a Quantum Spin Hall Insulator

Green's function Monte Carlo method combined with restricted Boltzmann machine approach to the frustrated J_(1)–J_(2)Heisenberg model

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Chinese Physics B 2022年第8期31卷 207-211页

作者： He-Yu Lin Rong-Qiang He zhong-yi lu Department of Physics Renmin University of ChinaBeijing 100872China

Restricted Boltzmann machine(RBM)has been proposed as a powerful variational ansatz to represent the ground state of a given quantum many-body *** the other hand,as a shallow neural network,it is found that the RBM is still hardly able to capture the characteristics of systems with large sizes or complicated *** order to find a way out of the dilemma,here,we propose to adopt the Green's function Monte Carlo(GFMC)method for which the RBM is used as a guiding wave *** demonstrate the implementation and effectiveness of the proposal,we have applied the proposal to study the frustrated J_(1)-J_(2)Heisenberg model on a square lattice,which is considered as a typical model with sign problem for quantum Monte Carlo *** calculation results demonstrate that the GFMC method can significantly further reduce the relative error of the ground-state energy on the basis of the RBM variational *** encourages to combine the GFMC method with other neural networks like convolutional neural networks for dealing with more models with sign problem in the future.

关键词： restricted Boltzmann machine Green's function Monte Carlo frustrated J_(1)–J_(2)Heisenberg model

A family of high-temperature ferromagnetic monolayers with locked spin-dichroism-mobility anisotropy: MnNX and CrCX(X=Cl,Br,I;C=S,Se,Te)

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Science Bulletin 2019年第5期64卷 293-300页

作者： Cong Wang Xieyu Zhou Linwei Zhou Ning-Hua Tong zhong-yi lu Wei Ji Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices Department of Physics Renmin University of China

Two-dimensional magnets have received increasing attention since Cr_2Ge_2Te_6 and CrI_3 were experimentally exfoliated and measured in 2017. Although layered ferromagnetic metals were demonstrated at room temperature, a layered ferromagnetic semiconductor with high Curie temperature(Tc) is yet to be unveiled. Here, we theoretically predicted a family of high Tcferromagnetic monolayers, namely MnNX and CrCX(X = Cl, Br and I; C = S, Se and Te). Their Tcvalues were predicted from over 100 K to near 500 K with Monte Carlo simulations using an anisotropic Heisenberg model. Eight members among them show semiconducting bandgaps varying from roughly 0.23 to 1.85 eV. These semiconducting monolayers also show extremely large anisotropy, i.e. ～10~1 for effective masses and ～10~2 for carrier mobilities, along the two in-plane lattice directions of these layers. Additional orbital anisotropy leads to a spin-locked linear dichroism, in different from previously known circular and linear dichroisms in layered *** with the mobility anisotropy, it offers a spin-, dichroism-and mobility-anisotropy *** results manifest the potential of this 2D family for both fundamental research and high performance spin-dependent electronic and optoelectronic devices.

关键词： Two-dimentional materials First-principles calculation Strong mobility anisotropy Spin-locked linear dichroism High-temperature ferromagnets Direct bandgap semic on ductor

Framework for Contrastive Learning Phases of Matter Based on Visual Representations

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Chinese Physics Letters 2023年第2期40卷 50-54页

作者： Xiao-Qi Han Sheng-Song Xu Zhen Feng Rong-Qiang He zhong-yi lu Department of Physics Renmin University of ChinaBeijing 100872China

A main task in condensed-matter physics is to recognize,classify,and characterize phases of matter and the corresponding phase transitions,for which machine learning provides a new class of research tools due to the remarkable development in computing power and *** much exploration in this new field,usually different methods and techniques are needed for different ***,we present SimCLP:a simple framework for contrastive learning phases of matter,which is inspired by the recent development in contrastive learning of visual *** demonstrate the success of this framework on several representative systems,including non-interacting and quantum many-body,conventional and *** is flexible and free of usual burdens such as manual feature engineering and prior *** only prerequisite is to prepare enough state ***,it can generate representation vectors and labels and hence help tackle other *** therefore paves an alternative way to the development of a generic tool for identifying unexplored phase transitions.

关键词： Visual hence classify