Subject Code:A04With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.Zhao Jun(赵俊)and Prof.Chen Gang(陈钢)at the State...Subject Code:A04With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.Zhao Jun(赵俊)and Prof.Chen Gang(陈钢)at the State Key Laboratory of Surface Physics and Department of Physics,Fudan University,found evidence for aquantum spin liquid state with a spinon Fermi surface in YbMgGaO_4,which was published in Nature(2016,540:559—562);see also'News and Views'Nature(2016,540:534—535).展开更多
The effect of anisotropy caused by a confining potential on the properties of fermionic cold atoms in a triangular optical lattice is systematically investigated by using the dynamical cluster approximation combined w...The effect of anisotropy caused by a confining potential on the properties of fermionic cold atoms in a triangular optical lattice is systematically investigated by using the dynamical cluster approximation combined with the continuous time quantum Monte-Carlo algorithm. The quantum phase diagrams which reflect the temperature-interaction relation and the competition between the anisotropic parameter and the interaction are presented with full consideration of the anisotropy of the system. Our results show that the system undergoes a transition from Fermi liquid to Mott insulator when the repulsive interaction reaches a critical value. The Kondo effect also can be observed in this system and the pseudogap is suppressed at low temperatures due to the Kondo effect. A feasible experiment protocol to observe these phenomena in an anisotropic triangular optical lattice with cold atoms is proposed, in which the hopping terms are closely related to the lattice confining potential and the atomic interaction can be adjusted via the Feshbach resonance.展开更多
用平面波展开法对二维光子晶体的电磁波理论及周期排列的电介质中电磁波的B loch波解进行了详细的推导,计算出以G aA s为背景的空气柱构成的二维三角格子光子晶体的能带结构,研究了H偏振和E偏振带隙宽度随填充比f的变化。计算结果表明,...用平面波展开法对二维光子晶体的电磁波理论及周期排列的电介质中电磁波的B loch波解进行了详细的推导,计算出以G aA s为背景的空气柱构成的二维三角格子光子晶体的能带结构,研究了H偏振和E偏振带隙宽度随填充比f的变化。计算结果表明,当f=0.8时,H偏振和E偏振出现重叠的最大绝对光子带隙,带隙位于0.458—0.529ωe(ωe=2πc/a,a为晶格常数,c为光速),带隙宽度为0.071ωe,相应的带隙波长范围为472.6—545.9nm,处于可见光波段。展开更多
Absolute band gaps of a two-dimensional triangular-lattice photonic crystal are calculated with the finite-difference time-domain method in this paper.Through calculating the photonic band structures of the triangular...Absolute band gaps of a two-dimensional triangular-lattice photonic crystal are calculated with the finite-difference time-domain method in this paper.Through calculating the photonic band structures of the triangular-lattice photonic crystal consisting of Ge rods immersed in air with different shapes,it is found that a large absolute band gap of 0.098 (2c/a) can be obtained for the structures with hollow triangular Ge rods immersed in air,corresponding to 19.8% of the middle frequency.The influence of the different factors on the width of the absolute band gaps is also discussed.展开更多
For a graph G and two positive integers j and k, an m-L（j, k）-edge-labeling of G is an assignment on the edges to the set {0, 1, 2,..., m}, such that adjacent edges which receive labels differ at least by j, and edg...For a graph G and two positive integers j and k, an m-L（j, k）-edge-labeling of G is an assignment on the edges to the set {0, 1, 2,..., m}, such that adjacent edges which receive labels differ at least by j, and edges which are distance two apart receive labels differ at least by k. The λj,k-number of G is the minimum m such that an m-L（j, k）-edge-labeling is admitted by G. In this article, the L（1, 2）-edge-labeling for the hexagonal lattice, the square lattice and the triangular lattice are studied, and the bounds for λj,k-numbers of these graphs are obtained.展开更多
We synthesized a quasi-two-dimensional distorted triangular lattice antiferromagnet Ca3CoNb2O9, in which the effective spin of Co2＋is 1/2 at low temperatures, whose magnetic properties were studied by dc susceptibili...We synthesized a quasi-two-dimensional distorted triangular lattice antiferromagnet Ca3CoNb2O9, in which the effective spin of Co2＋is 1/2 at low temperatures, whose magnetic properties were studied by dc susceptibility and magnetization techniques. The x-ray diffraction confirms the quality of our powder samples. The large Weiss constant θCW --55 K and the low Neel temperature TN- 1.45 K give a frustration factor f =｜ θCW/TN｜≈ 38, suggesting that Ca3 Co Nb2O9resides in strong frustration regime. Slightly below TN, deviation between the susceptibility data under zero-field cooling（ZFC）and field cooling（FC） is observed. A new magnetic state with 1/3 of the saturate magnetization Ms is suggested in the magnetization curve at 0.46 K. Our study indicates that Ca3 Co Nb2O9is an interesting material to investigate magnetism in triangular lattice antiferromagnets with weak anisotropy.展开更多
文摘Subject Code:A04With the support by the National Natural Science Foundation of China and the Ministry of Science and Technology of China,the research team led by Prof.Zhao Jun(赵俊)and Prof.Chen Gang(陈钢)at the State Key Laboratory of Surface Physics and Department of Physics,Fudan University,found evidence for aquantum spin liquid state with a spinon Fermi surface in YbMgGaO_4,which was published in Nature(2016,540:559—562);see also'News and Views'Nature(2016,540:534—535).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11074141,11174169,and 10934010)the National Natural Science Foundation of China and Research Grant Council(NSFC/RGC)Joint Research Scheme(Grants No.11061160490)the National Basic Research Program of China(Grants Nos.2011CB921502,2012CB821305,2010CB922904,2009CB930701,and 2009CB929202)
文摘The effect of anisotropy caused by a confining potential on the properties of fermionic cold atoms in a triangular optical lattice is systematically investigated by using the dynamical cluster approximation combined with the continuous time quantum Monte-Carlo algorithm. The quantum phase diagrams which reflect the temperature-interaction relation and the competition between the anisotropic parameter and the interaction are presented with full consideration of the anisotropy of the system. Our results show that the system undergoes a transition from Fermi liquid to Mott insulator when the repulsive interaction reaches a critical value. The Kondo effect also can be observed in this system and the pseudogap is suppressed at low temperatures due to the Kondo effect. A feasible experiment protocol to observe these phenomena in an anisotropic triangular optical lattice with cold atoms is proposed, in which the hopping terms are closely related to the lattice confining potential and the atomic interaction can be adjusted via the Feshbach resonance.
文摘用平面波展开法对二维光子晶体的电磁波理论及周期排列的电介质中电磁波的B loch波解进行了详细的推导,计算出以G aA s为背景的空气柱构成的二维三角格子光子晶体的能带结构,研究了H偏振和E偏振带隙宽度随填充比f的变化。计算结果表明,当f=0.8时,H偏振和E偏振出现重叠的最大绝对光子带隙,带隙位于0.458—0.529ωe(ωe=2πc/a,a为晶格常数,c为光速),带隙宽度为0.071ωe,相应的带隙波长范围为472.6—545.9nm,处于可见光波段。
基金supported by the National Natural Science Foundation of China (Grant No. 10904176)the National Key Basic Research Special Foundation of China (Grant No. 2006CB921702)+1 种基金the Research Foundation of the State Ethnic Affairs Commission of China (Grant No. 09ZY012)the NMOE Project of China (Grant No. 200911002)
文摘Absolute band gaps of a two-dimensional triangular-lattice photonic crystal are calculated with the finite-difference time-domain method in this paper.Through calculating the photonic band structures of the triangular-lattice photonic crystal consisting of Ge rods immersed in air with different shapes,it is found that a large absolute band gap of 0.098 (2c/a) can be obtained for the structures with hollow triangular Ge rods immersed in air,corresponding to 19.8% of the middle frequency.The influence of the different factors on the width of the absolute band gaps is also discussed.
基金Supported by the National Natural Science Foundation of China(10971025 and 10901035)
文摘For a graph G and two positive integers j and k, an m-L（j, k）-edge-labeling of G is an assignment on the edges to the set {0, 1, 2,..., m}, such that adjacent edges which receive labels differ at least by j, and edges which are distance two apart receive labels differ at least by k. The λj,k-number of G is the minimum m such that an m-L（j, k）-edge-labeling is admitted by G. In this article, the L（1, 2）-edge-labeling for the hexagonal lattice, the square lattice and the triangular lattice are studied, and the bounds for λj,k-numbers of these graphs are obtained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374364 and 11222433)the National Basic Research Program of China(Grant No.2011CBA00112)+2 种基金Research at Mc Master University supported by the Natural Sciences and Engineering Research CouncilWork at North China Electric Power University supported by the Scientific Research Foundation for the Returned Overseas Chinese ScholarsState Education Ministry
文摘We synthesized a quasi-two-dimensional distorted triangular lattice antiferromagnet Ca3CoNb2O9, in which the effective spin of Co2＋is 1/2 at low temperatures, whose magnetic properties were studied by dc susceptibility and magnetization techniques. The x-ray diffraction confirms the quality of our powder samples. The large Weiss constant θCW --55 K and the low Neel temperature TN- 1.45 K give a frustration factor f =｜ θCW/TN｜≈ 38, suggesting that Ca3 Co Nb2O9resides in strong frustration regime. Slightly below TN, deviation between the susceptibility data under zero-field cooling（ZFC）and field cooling（FC） is observed. A new magnetic state with 1/3 of the saturate magnetization Ms is suggested in the magnetization curve at 0.46 K. Our study indicates that Ca3 Co Nb2O9is an interesting material to investigate magnetism in triangular lattice antiferromagnets with weak anisotropy.
