Inspired by the recent discovery of breathing kagome materials Nb_(3)Cl_(8) and Nb_(3)TeCl_(7),we have explored the influence of the breathing effect on the Hubbard model of the kagome lattice.Utilizing the determinan...Inspired by the recent discovery of breathing kagome materials Nb_(3)Cl_(8) and Nb_(3)TeCl_(7),we have explored the influence of the breathing effect on the Hubbard model of the kagome lattice.Utilizing the determinant quantum Monte Carlo method,we first investigated the average sign problem in the breathing kagome lattice,which is influenced by both the breathing strength and the interaction strength.Secondly,we calculated the electronic kinetic energy,the direct current conductivity,and the electronic density of states at the Fermi level to determine the critical interaction strength for the metal-insulator transition.Our results indicate that the breathing effect,in conjunction with the interaction strength,drives the kagome system from a metal to an insulator.Finally,we evaluated the magnetic properties and constructed a phase diagram incorporating both transport and magnetic properties.The phase diagram reveals that as the interaction strength increases,the system transitions from a paramagnetic metal to a Mott insulator.Our research provides theoretical guidance for utilizing the breathing effect to control the band gaps,conductivity,and magnetic properties of kagome materials with electronic interactions.展开更多
Recent discovery of high transition temperature superconductivity in La_(3)Ni_(2)O_(7) has sparked renewed theoretical and experimental interests in unconventional superconductivity. It is crucial to understand the in...Recent discovery of high transition temperature superconductivity in La_(3)Ni_(2)O_(7) has sparked renewed theoretical and experimental interests in unconventional superconductivity. It is crucial to understand the influence of various factors on its superconductivity. By refining the determinant quantum Monte Carlo algorithm, we characterize the parameter dependence of the superconducting transition temperature within a bilayer Hubbard model, which is sign-problem-free at arbitrary filling. A striking feature of this model is its similarity to the bilayer nickelate-based superconductor La_(3)Ni_(2)O_(7), where superconductivity emerges from the bilayer NiO_(2) planes.We find that interlayer spin-exchange J is critical to interlayer pairing, and that on-site interaction U contributes negatively to superconductivity at low doping levels but positively at high doping levels. Our findings can provide a reference for the next step in theoretical research on nickelate-based superconductors.展开更多
Using the determinant quantum Monte Carlo method,we explore a rich phase diagram featuring strain-induced metal-insulator and magnetic phase transitions in an interacting two-dimensional Dirac fermion system.Asymmetri...Using the determinant quantum Monte Carlo method,we explore a rich phase diagram featuring strain-induced metal-insulator and magnetic phase transitions in an interacting two-dimensional Dirac fermion system.Asymmetric strain applied along the zigzag crystal direction drives the semimetallic regime into a band-insulating phase,or it breaks the antiferromagnetic order of the Mott insulator,inducing a nonmagnetic insulating phase under strong correlations.The critical strain required for band gap opening or for a transport phase transition is significantly reduced in the presence of Coulomb repulsion,while increasing interaction strength makes it more difficult for strain to induce a nonmagnetic phase transition.In addition,we measure in detail the band gap modulation by strain and identify a doping effect whereby doping inhibits band gap opening.Our results provide an effective way to tune the transport gap,which could help extend the applications of graphene,whose zero band gap currently limits its use.展开更多
Antimony(Sb)is a toxic and carcinogenic element that often enters soil in the form of antimony trioxide(Sb_(2)O_(3))and coexists with manganese(Mn)in weakly alkaline conditions.Mn oxides such as birnessite have been f...Antimony(Sb)is a toxic and carcinogenic element that often enters soil in the form of antimony trioxide(Sb_(2)O_(3))and coexists with manganese(Mn)in weakly alkaline conditions.Mn oxides such as birnessite have been found to promote the oxidative dissolution of Sb_(2)O_(3),but few researches concerned the co-transformations of Sb_(2)O_(3) and Mn(II)in environment.This study investigated themutual effect of abiotic oxidation of Mn(II)and the coupled oxidative dissolution of Sb_(2)O_(3).The influencing factors,such as Mn(II)concentrations,pH and oxygen were also discussed.Furthermore,their co-transformed mechanism was also explored based on the analysis of Mn(II)oxidation products with or without Sb_(2)O_(3) using XRD,SEM and XPS.The results showed that the oxidative dissolution of Sb_(2)O_(3) was enhanced under higher pH and higher Mn(II)loadings.With a lower Mn(II)concentration such as 0.01 mmol/L Mn(II)at pH 9.0,the improved dissolution of Sb_(2)O_(3) was attributed to the generation of dissolved intermediate Mn(III)species with strong oxidation capacity.However,under higher Mn(II)concentrations,both amorphous Mn(III)oxides and intermediate Mn(III)species were responsible for promoting the oxidative dissolution of Sb_(2)O_(3).Most released Sb(∼72%)was immobilized by Mn oxides and Sb(V)was dominant in the adsorbed and dissolved total Sb.Meanwhile,the presence of Sb_(2)O_(3) not only inhibited the removal of Mn(II)by reducing Mn(III)to Mn(II)but also affected the final products of Mn oxides.For example,amorphous Mn oxides were formed instead of crystalline Mn(III)oxides,such as MnOOH.Furthermore,rhodochrosite(MnCO_(3))was formed with the high Mn(II)/Sb_(2)O_(3) ratio,but without being observed in the low Mn(II)/Sb_(2)O_(3) ratio.The results of study could help provide more understanding about the fate of Sb in the environment and the redox transformation of Mn.展开更多
基金supported by the National Science Foundation of China(Grant No.12474218)Beijing Natural Science Foundation(Grant Nos.1242022 and 1252022).
文摘Inspired by the recent discovery of breathing kagome materials Nb_(3)Cl_(8) and Nb_(3)TeCl_(7),we have explored the influence of the breathing effect on the Hubbard model of the kagome lattice.Utilizing the determinant quantum Monte Carlo method,we first investigated the average sign problem in the breathing kagome lattice,which is influenced by both the breathing strength and the interaction strength.Secondly,we calculated the electronic kinetic energy,the direct current conductivity,and the electronic density of states at the Fermi level to determine the critical interaction strength for the metal-insulator transition.Our results indicate that the breathing effect,in conjunction with the interaction strength,drives the kagome system from a metal to an insulator.Finally,we evaluated the magnetic properties and constructed a phase diagram incorporating both transport and magnetic properties.The phase diagram reveals that as the interaction strength increases,the system transitions from a paramagnetic metal to a Mott insulator.Our research provides theoretical guidance for utilizing the breathing effect to control the band gaps,conductivity,and magnetic properties of kagome materials with electronic interactions.
基金supported by the National Natural Science Foundation of China (Grant Nos.12234016,12174317 for C.Wu,and 12474218 for R.Ma,Z.Fan,and T.Ma)Beijing Natural Science Foundation (Grant No.1242022 for R.Ma,Z.Fan,and T.Ma)the New Cornerstone Science Foundation。
文摘Recent discovery of high transition temperature superconductivity in La_(3)Ni_(2)O_(7) has sparked renewed theoretical and experimental interests in unconventional superconductivity. It is crucial to understand the influence of various factors on its superconductivity. By refining the determinant quantum Monte Carlo algorithm, we characterize the parameter dependence of the superconducting transition temperature within a bilayer Hubbard model, which is sign-problem-free at arbitrary filling. A striking feature of this model is its similarity to the bilayer nickelate-based superconductor La_(3)Ni_(2)O_(7), where superconductivity emerges from the bilayer NiO_(2) planes.We find that interlayer spin-exchange J is critical to interlayer pairing, and that on-site interaction U contributes negatively to superconductivity at low doping levels but positively at high doping levels. Our findings can provide a reference for the next step in theoretical research on nickelate-based superconductors.
基金supported by the National Natural Science Foundation of China(Grant No.12474218)the Beijing Natural Science Foundation(Grant No.1242022)the Guangxi Key Laboratory of Precision Navigation Technology and Application,Guilin University of Electronic Technology(Grant No.DH202322)。
文摘Using the determinant quantum Monte Carlo method,we explore a rich phase diagram featuring strain-induced metal-insulator and magnetic phase transitions in an interacting two-dimensional Dirac fermion system.Asymmetric strain applied along the zigzag crystal direction drives the semimetallic regime into a band-insulating phase,or it breaks the antiferromagnetic order of the Mott insulator,inducing a nonmagnetic insulating phase under strong correlations.The critical strain required for band gap opening or for a transport phase transition is significantly reduced in the presence of Coulomb repulsion,while increasing interaction strength makes it more difficult for strain to induce a nonmagnetic phase transition.In addition,we measure in detail the band gap modulation by strain and identify a doping effect whereby doping inhibits band gap opening.Our results provide an effective way to tune the transport gap,which could help extend the applications of graphene,whose zero band gap currently limits its use.
基金This work was supported by the National Natural Science Foundation of China(Nos.42077184,41772251 and 41521001)the National Key Research and Development Program(No.2018YFC1801700).
文摘Antimony(Sb)is a toxic and carcinogenic element that often enters soil in the form of antimony trioxide(Sb_(2)O_(3))and coexists with manganese(Mn)in weakly alkaline conditions.Mn oxides such as birnessite have been found to promote the oxidative dissolution of Sb_(2)O_(3),but few researches concerned the co-transformations of Sb_(2)O_(3) and Mn(II)in environment.This study investigated themutual effect of abiotic oxidation of Mn(II)and the coupled oxidative dissolution of Sb_(2)O_(3).The influencing factors,such as Mn(II)concentrations,pH and oxygen were also discussed.Furthermore,their co-transformed mechanism was also explored based on the analysis of Mn(II)oxidation products with or without Sb_(2)O_(3) using XRD,SEM and XPS.The results showed that the oxidative dissolution of Sb_(2)O_(3) was enhanced under higher pH and higher Mn(II)loadings.With a lower Mn(II)concentration such as 0.01 mmol/L Mn(II)at pH 9.0,the improved dissolution of Sb_(2)O_(3) was attributed to the generation of dissolved intermediate Mn(III)species with strong oxidation capacity.However,under higher Mn(II)concentrations,both amorphous Mn(III)oxides and intermediate Mn(III)species were responsible for promoting the oxidative dissolution of Sb_(2)O_(3).Most released Sb(∼72%)was immobilized by Mn oxides and Sb(V)was dominant in the adsorbed and dissolved total Sb.Meanwhile,the presence of Sb_(2)O_(3) not only inhibited the removal of Mn(II)by reducing Mn(III)to Mn(II)but also affected the final products of Mn oxides.For example,amorphous Mn oxides were formed instead of crystalline Mn(III)oxides,such as MnOOH.Furthermore,rhodochrosite(MnCO_(3))was formed with the high Mn(II)/Sb_(2)O_(3) ratio,but without being observed in the low Mn(II)/Sb_(2)O_(3) ratio.The results of study could help provide more understanding about the fate of Sb in the environment and the redox transformation of Mn.
