Wilson ratio of a Tomonaga-Luttinger liquid in a spin-1/2 Heisenberg ladder

Using micromechanical force magnetometry, we have measured the magnetization of the strong-leg spin-1/2 ladder compound (C(7)H(10)N)(2)CuBr(2) at temperatures down to 45 mK. Low-temperature magnetic susceptibility as a function of field exhibits a maximum near the critical field H(c) at which the magnon gap vanishes, as expected for a gapped one-dimensional antiferromagnet. Above H(c) a clear minimum appears in the magnetization as a function of temperature, as predicted by theory. In this field region, the susceptibility in conjunction with our specific-heat data yields the Wilson ratio R(W). The result supports the relation R(W)=4K, where K is the Tomonaga-Luttinger-liquid parameter.     

Field-induced Tomonaga-Luttinger liquid phase of a two-leg spin-1/2 ladder with strong leg interactions

We study the magnetic-field-induced quantum phase transition from a gapped quantum phase that has no magnetic long-range order into a gapless phase in the spin-1/2 ladder compound bis(2,3-dimethylpyridinium) tetrabromocuprate (DIMPY). At temperatures below about 1 K, the specific heat in the gapless phase attains an asymptotic linear temperature dependence, characteristic of a Tomonaga-Luttinger liquid. Inelastic neutron scattering and the specific heat measurements in both phases are in good agreement with theoretical calculations, demonstrating that DIMPY is the first model material for an S=1/2 two-leg spin ladder in the strong-leg regime.     

Notes on Multi-linear Variable Separation Approach

The multi-linear variable separation approach method is very useful to solve (2+1)-dimensional integrable systems. In this letter, we extend this method to solve (1+1)-dimensional Boiti system, (2+1)-dimensional Burgers system, (2+1)-dimensional breaking soliton system, and (2+1)-dimensional Maccari system. Some new exact solutions are obtained and the universal formula obtained from many (2+1)-dimensional systems is extended or modified.     

弱耦合自旋1/2二核系统二维动态NMR谱

二维动态NMR谱通常可由三脉冲实验得到。但如果核系统有标量耦合,就有可能混淆实验所得的信息。本文在Liouvelle空间中求出二核弱耦合系统的二维理论动态谱,给出AX(I=1/2)系统中的密度矩阵的解析解。文中指出:(1)在梯度脉冲作用之后,密度矩阵将留下z分量、零量子相干和双量子相干。(2)标量耦合与交换作用、弛豫作用的影响不同。前者只对零量子相干及双量子相干有贡献。如果实验得当,有希望消除标量耦合对动态谱的干扰。 关键词：     

CONFINEMENT PROPERTIES OF PURE GAUGE FIELCS ON COSET SPACE OF THE NON-ABELIAN CHIRAL GROUP

In this paper the method of lattlce gauge theories is applied to the investigation of the effect of coset pure gauge fields of the non-Abelian chiral group on the confinement properties of a system. In particular, the current-current propagator of the coset G/H=SU(2)_L×(2)_r/SU(2) model is calculated. Then it IS found that the pure gauge fields-on coset space only offer a perimeter law factor which does not change the confinement properties of a physical system.     

On Peakon and Kink-peakon Solutions to a (2 + 1) Dimensional Generalized Camassa-Holm Equation

In this paper, we study a (2 + 1)-dimensional generalized Camassa-Holm (2dgCH) equation with both quadratic and cubic nonlinearity. We derive a peaked soliton (peakon) solution, double-peakon solutions, and kink-peakon solutions. In particular, weak kink - peakon solution is the first time to address in the 2 + 1-dimensional integrable system.     

Entanglement detection in the mixed-spin Ising–XY model

In the present work, we initially verify anisotropy effect on the heat capacity of a mixed-three-spin(1/2,1,1/2) system(where spins(1/2,1/2) have XY interaction and spins(1,1/2) have Ising interaction together) at finite temperatures, then,the pairwise entanglement for spins(1/2,1/2), by means of negativity(as a measure of entanglement) as a function of the temperature T, homogeneous magnetic field B, and anisotropy parameter γ is investigated. In addition, we show that one can find magnetic phase transition points for the spins(1/2,1/2) at finite temperatures and understand properly their behavior with respect to the magnetic field and the anisotropy parameter, via the negativity function. An interval of the magnetic field from the negativity diagram of the spins(1/2,1/2) is presented in which quantum phase transition occurs for the tripartite mixed-three-spin system. Finally, some new interesting entanglement witnesses are introduced by using non-degenerate perturbation theory for the mixed-three-spin system.     

Residual symmetry,interaction solutions,and conservation laws of the(2+1)-dimensional dispersive long-wave system

We explore the(2+1)-dimensional dispersive long-wave(DLW) system. From the standard truncated Painlev′e expansion, the B¨acklund transformation(BT) and residual symmetries of this system are derived. The introduction to an appropriate auxiliary dependent variable successfully localizes the residual symmetries to Lie point symmetries. In particular, it is verified that the(2+1)-dimensional DLW system is consistent Riccati expansion(CRE) solvable. If the special form of(CRE)-consistent tanh-function expansion(CTE) is taken, the soliton-cnoidal wave solutions and corresponding images can be explicitly given. Furthermore, the conservation laws of the DLW system are investigated with symmetries and Ibragimov theorem.     

Study on two-cell stimulated Brillouin scattering system with mixture medium

In this paper,a method of choosing mixture medium in two-cell stimulated Brillouinscattering(SBS)system to improve the system performance is proposed.The Brillouin frequency shift(BFS)of mixture medium varies with the mixing ratio andthus the difference of the BFS between the two cells can be eliminated.The two-cellSBS system with acetone(C3H6O)in its generator cell and mixture liquid ofCCl4/C2Cl4 in its amplifier cell is investigated.The C3H6O has a high optical breakdown threshold and the mixture liquid of CCl4/C2Cl4 has a small absorption coeffi-cient and the same BFS as that of C3H6O when the volume fraction of CCl4 is 4%.Compared with two-cell SBS system with the same liquid(C2Cl4)or different liquid(C3H6O and C2Cl4)in generator and amplifier cell,the SBS system with mixture liq-uid(CCl4/C2Cl4)in amplifier cell and C3H6O in generator cell improves thepower-load,energy reflectivity(ER),phase conjugation(PC)fidelity and ER stabil-ity.     

The two-dimensional alternative binary L-J system: liquid——gas phase diagram

A two-dimensional (2D) binary system without considering the　Lennard-Jones (L-J) potential has been studied by using the　Collins model. In this paper, we introduce the L-J potential　into the 2D binary system and consider the existence of the　holes that are called the ``molecular fraction". The liquid--gas　phase diagram of the 2D alternative binary L-J system is obtained. The　results are quite analogous to the behaviour of 3D substances.     

含Maxwell–Chern–Simons项CP1非线性σ模型的分数自旋和分数统计性质

在(2+1)维时空中研究了含Maxwell-Chern-Simons(MCS)项的CP¹非线性σ模型的量子对称性质.取库仑规范,用Faddeev-Senjanovic路径积分量子化方案对该系统进行量子化.根据约束Hamilton系统的量子对称性质,在量子水平上得到了系统分数自旋性质     

Soft phonon, dynamical fluctuations, and a reversible phase transition: indium chains on silicon

The In/Si(111)-(4 x 1) surface is a paradigmatic example of a quasi-one-dimensional system showing a reversible structural and electronic (metal-insulator) phase transition when the temperature is lowered. In this work, we use first-principles simulation techniques to uncover the atomic and electronic origin of this controversial transition. Our calculations show that the ground state consists of insulating (4 x 2) indium chains with a weak interchain coupling that induces opposite shear distortions in alternate chains. First-principles molecular dynamics simulations show that the (4 x 1) <--> (8 x 2) phase transition is due to the "dynamical fluctuations" the system undergoes when, at high temperature, it fluctuates chaotically between degenerate ground states. The metallicity of the In/Si(111)-(4 x 1) surface is related to the low energy cost for the shear distortion.     

利用级联式能量传递的有机电致发光器件

为了提高掺杂型有机电致发光器件(OLED)中主体发光材料与客体荧光染料间能量传递的效率,2-对联苯-8-羟基喹啉锌(Zn ₂)作为NPB : DCJTB掺杂体系的能量助传递剂,制备了结构如:ITO/NPB/NPB : DCJTB/Zn ₂/BCP/Al的有机电致发光器件。助传递剂Zn ₂的加入,能够两次利用Frster能量转移,实现NPB向DCJTB级联式的能量传递过程,提高低浓度时掺杂染料DCJTB红光发射的纯度;此外,还探讨了三者间能量传递的有效距离,即当助传递剂与掺杂体系的距离在小于10 nm的范围内,其参与能量传递的效率随着距离的增加而逐渐下降。     

惰性气体对HFCVD沉积金刚石气相基团的影响

发射光谱法是对等离子进行在线诊断的常用方法。在丙酮/H_2、丙酮/H_2/He和丙酮/H_2/Ar三种体系中,对热丝化学气相沉积金刚石薄膜过程中的等离子体进行了在线测量。研究了不同体积分数的惰性气体对等离子体中各活性基团强度的影响,以及CH,Hβ与C_2的相对强度的比值、电子温度的大小随惰性气体体积分数的变化关系。结果表明,各基团的强度随着惰性气体体积分数的增加呈现上升趋势,且加入同体积分数的氩气比加入氦气的影响更大;CH,Hβ与C_2的相对强度比值、电子温度随着惰性气体体积分数的增加而呈现下降趋势,且在丙酮/H_2/Ar体系中要比丙酮/H_2/He体系中小。     

三元混合制冷剂R290+R600a+N2汽液相平衡实验研究

在氢气液化工艺中,预冷循环是重要的一环,其中混合制冷剂(mixed refrigerant,MR)预冷循环是单位能耗比较低的,故对MR性能的优化显得尤为重要.为此利用液相单相循环法搭建汽液相平衡(Vapor-liquid equilibrium,VLE)实验系统,研究了R290+R600a+N₂三元体系的VLE性质,在273.15 K～323.15 K的温度范围内,对三元混合工质R290+R600a+N₂进行实验研究,并获得18组实验数据.同时使用Peng-Pobinson-Stryjek-Vera (PRSV)状态方程结合van der Waals(vd W)混合法则对R290+R600a、R290+N₂、R600a+N₂三组二元体系的VLE文献数据进行了拟合计算,得到二元交互作用系数,拟合结果与文献数据吻合良好.以此为基础,推算该三元体系的VLE性质.最后将实验数据与计算结果对比表明,体系压力平均相对偏差AARDp为0.85%,系统组分R290、R600a和N₂的气相平均绝...     

About a nonadditivity of energy and entropy

The mathematical expression of nonadditivity X(1 ?? 2) = X(1) + X(2) + ??X(1)X(2) has been frequently used for the development of statistical physics for nonadditive system, where X is entropy or energy, and ?? is hoped to be a parameter characterising the nonadditive property of the composite system (1 ?? 2). Here we show that this relationship cannot hold exactly. In general, ?? in this expression inevitably depends on how a given system with constant X(1 ?? 2) is divided into subsystems 1 and 2. Hence mathematical problems may arise when it is used to characterise the nonadditivity of the system. Nevertheless, under some conditions, it is possible to use it as a good approximation.     

Novel metallic behavior in two dimensions

Experiments on a sufficiently disordered two-dimensional (2D) electron system in silicon reveal a new and unexpected kind of metallic behavior, where the conductivity decreases as sigma(n(s),T) = sigma(n(s),T = 0)+A(n(s))T(2) (where n(s) is carrier density) to a nonzero value as temperature T-->0. In 2D, the existence of a metal with dsigma/dT>0 is very surprising. In addition, a novel type of a metal-insulator transition obtains, which is unlike any known quantum phase transition in 2D.     

低维体系的相变和叠套

与一维体系不同，二维体系费密面的叠套是不完全的，此种叠套的偏离会显著地减弱体系的不稳定性．定量地研究了叠套偏离对Peierls相变的影响，并确定了叠套偏离的限度，超过此值，Peierls相变被抑制，这有利于进入超导态． 关键词：     

Doppler程序对C、N掺杂金红石型TiO_2的理论研究

本文在密度泛函理论和广义梯度近似(GGA)的基础上,应用Doppler程序计算了C掺杂、N掺杂、C-N共掺杂TiO_2体系的正电子湮没寿命,并且从理论上给出TiO_2体系不同缺陷处的符合多普勒展宽能谱.     

CuCl_2-H_2O体系和FeCl_3-H_2O体系络合物拉曼光谱研究与溶液拉曼定量分析探索

详细研究了CuCl2-H2O体系和FeCl3-H2O体系络合物拉曼峰。对于CuCl2-H2O体系,认为286cm-1峰可能是[CuCl4]2-和[CuCl6]4-等Cu2+和Cl-形成的各种形式络合物的特征峰叠加的结果,412 cm-1峰可能是以[Cu(H2O)4]2+和[Cu(H2O)6]2+为主的Cu2+的水合物的特征峰叠加在一起形成的;通过对特征峰参数的分析得到了286和412 cm-1特征峰的强度与3 400 cm-1左右水的O—H伸缩振动最强峰强度之比(I1/I3 400和I2/I3 400)以及这两个特征峰的积分面积(A1和A2)和浓度的定量关系曲线,从络合物角度实现了对CuCl2溶液的定量分析。对于FeCl3-H2O体系认为173和331 cm-1两个特征峰可能都是归属于FeCl3在水溶液中最常见的络合形式—[FeCl4]-,173 cm-1峰形很宽可能是由于Fe3+和Cl-形成的其他各种形式络合物,如[FeCl]2+,[FeCl2]+等的特征峰叠加的结果,331 cm-1之后的弱宽峰可能是以[Fe(H2O)4]3+,[Fe(H2O)6]3+为主的Fe3+的水合物的特征峰叠加在一起而形成的;通过...