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1.
陆展鹏  魏兴波  刘天帅  陈阿海  高先龙 《物理学报》2017,66(12):126701-126701
通过数值方法求解了有限温度下一维均匀Hubbard模型的热力学Bethe-ansatz方程组,得到了在给定温度和相互作用强度情况下,比热c、磁化率χ和压缩比κ随化学势μ的变化图像.基于有限温度下一维均匀Hubbard模型的精确解,利用化学势(μ)-泛函理论研究了一维谐振势下的非均匀Hubbard模型,给出了金属态和Mott绝缘态下不同温度情况时局域粒子密度n_i和局域压缩比_κi随格点的变化情况.  相似文献   

2.
熊元生  易林  姚凯伦 《物理学报》1994,43(12):2052-2058
利用稳态量子replica对称自旋玻璃理论,研究了具有Dzyaloshinskii-Moriya(缩写为DM)各向异性相互作用的Sherrington-Kirkpatrick自旋玻璃在外场中的热力学性质。数值计算了不同外场和各向异性作用的自旋为1/2和1的熵、比热、局域磁化率和相应的序参数随温度的变化。发现局域磁化率与热场动力学的结果相符合。特别地,本文的比热-温度曲线能满意地解释Brodale等实验观察到的不同磁场下的交叉特征。关键词:  相似文献   

3.
童培庆 《物理学报》1993,42(10):1543-1549
分别给出周期和自由边界条件下求解一维Fibonacci准周期Frustrated Ising模型的配分函数的方法。研究它的低温热力学性质,发现当温度趋于零时,其热力学函数在参数b/J=2/(2m+1)(m为正整数)处发生尖锐的变化。分析了零温时系统在不同参数范围内的基态构形,对计算的结果进行了解释。关键词:  相似文献   

4.
基于巨正则系综理论和数值模拟方法,研究有限尺度下弱相互作用费米气体的热力学性质,给出系统低温下的化学势、能量及热容量的解析式,分析弱相互作用、有限尺度效应对系统热力学性质的影响.研究表明,有限尺度和排斥相互作用增大了系统的化学势、能量,吸引相互作用减小了系统的化学势、能量.相互作用受到尺度的调制,尺度变大,相互作用影响变小,相互作用和尺度效应都受到温度的调制,温度升高,相互作用和尺度的影响减小.尺度和相互作用的一级修正对热容量无影响.  相似文献   

5.
利用相干态有效势方法,本文重新研究了Gross-Neveu(GN)模型,对于任意分量N的费米场得到了一个\"非平凡\"的 \"Autonomous\"理论.N→∞时,该理论与GN的结果等价. \"Autonomous\"理论的动力学破缺的对称性将在某个临界度得到恢复,在破缺相元激发的质量仅仅与温度有关而与N无关.  相似文献   

6.
本利用平均场近似,研究了负UK伯德模型中η对超导体的热力性质,给出了临界磁场与温度的关系,式,求出临界温度处的比热跃迁,它们与已知的实验符合行比较好。  相似文献   

7.
论述了主要空分流体的临界区热力学性质,总结了这些流体目前最为准确的临界参数、临界指数及临界系数实验数据,并与多种模型的计算结果进行了比较.在整合多种流体临界区饱和密度实验数据的基础上,利用幂定律拟合方法得到了统一的临界指数β.该结果与实验数据及重正化群理论计算结果吻合良好.  相似文献   

8.
利用实时格林函数方法,本文推广汤川势至有限温度和有限密度情况.我们发现,σ介子的有效质量随温度和/或密度升高而减小.本文还对由实时格林函数给出的结果和由虚时格林函数给出的结果进行了比较.  相似文献   

9.
李晓凤  刘中利  彭卫民  赵阿可 《物理学报》2011,60(7):76501-076501
利用密度泛函理论的平面波赝势方法预测研究了CaPo从岩盐结构(B1结构)到氯化铯结构(B2结构)的相变以及B1结构CaPo高压下的弹性性质以及热力学性质等.通过等焓原理发现B1→B2的相变压力为22.8GPa. 同时计算了B1结构CaPo高压下的弹性常数以及剪切模量、杨氏模量等相关弹性参数,结果发现当压力超过20GPa时,B1结构CaPo开始不稳定了,这和等焓原理所得结果相符合. 最后通过Debye模型成功获取了B1结构C关键词:相变弹性性质热力学性质CaPo  相似文献   

10.
邓强  颜骏 《物理学报》2008,57(7):3978-3982
研究了具有奇异物质作用的二维暗能量星模型,推导出了场方程和星体平衡方程;并获得了一些解析解,计算出了星体质量.另外,还研究了温度对星体质量的影响,发现几种情况下星体总质量都具有上限.关键词:暗能量星奇异物质有限温度  相似文献   

11.
    
We investigate the quantum temporal steering (TS), i.e., a temporal analogue of Einstein‐Podolsky‐Rosen steering, in a dephasing channel which is modeled by a central spin half surrounded by a spin‐1/2 XY chain where quantum phase transition happens. The TS parameter and the TS weight are employed to characterize the TS dynamics. We analytically obtain the dependence of on the decoherence factor. The numerical results show an obvious suppression of and when the XY chain approaches to the critical point. In view of the significance of quantum channel, we develop a new concept, TS weight power, in order to quantify the capacity of the quantum channel in dominating TS behavior. This new quantity enables us to indicate the quantum criticality of the environment by the quantum correlation of TS in the coupled system.  相似文献   

12.
    
The propagation of cracks in two-dimensional decagonal model quasicrystals is studied under mode I loading by means of molecular dynamics simulations. In particular, we investigate the dependence on temperature, applied load and underlying structure. The samples are endowed with an atomically sharp crack and strained by linear scaling of the displacement field. Three different regimes of propagation and discernible with increasing temperature. For low temperatures the crack velocity increases monotonically with increasing applied load. We observe that the crack follows the path of dislocations nucleated at its tip. For temperatures above 0.3?T m, where T m is the melting temperature, the crack does not remain atomically sharp but becomes blunt spontaneously. In the temperature range between 0.7?T m and 0.8?T m the quasicrystal fails by nucleation, growth and coalescence of microvoids. This gradual dislocation-free crack extension is caused by plastic deformation which is mediated by localized rearrangements comparable with the so-called shear transformation zones. These are also observed in amorphous solids. Thus, at low temperatures the crack propagates along crystallographic planes just as in periodic crystals, whereas at high temperatures a glass-like behaviour is dominant.  相似文献   

13.
陈相君  张卫宁  霍雷 《中国物理 C》1999,23(11):1083-1089
用热传播子的实时形式计算了有限温度QCD热力学势的一级修正,并讨论了夸克胶子等离子体中的压强修正以及强子退禁闭相变临界温度的修正.  相似文献   

14.
A stochastic local limited one-dimensional rice-pile model is numerically investigated. The distributions for avalanche sizes have a clear power-law behavior and it displays a simple finite size scaling. We obtain the avalanche exponents Ts= 1.54±0.10,βs = 2.17±0.10 and TT = 1.80±0.10, βT =1.46 ± 0.10. This self-organized critical model belongs to the same universality class with the Oslo rice-pile model studied by K. Christensen et al. [Phys. Rev. Lett. 77 (1996) 107], a rice-pile model studied by L.A.N. Amaral et al. [Phys. Rev. E 54 (1996) 4512], and a simple deterministic self-organized critical model studied by M.S. Vieira [Phys. Rev. E 61 (2000) 6056].  相似文献   

15.
In this work, we investigate the thermal entanglement for interacting spin systems , by varying the parameters of temperature T, direction and magnetic field B. PACS numbers: 03.67.Mn, 03.65.Ud, 05.30.Cd, 73.43.Nq  相似文献   

16.
    
A stochastic local limited one-dimensional rice-pile model is numerically investigated. The distributions for avalanche sizes have a clear power-law behavior and it displays a simple finite size scaling. We obtain the avalanche exponents τs=1.54±0.10, βs=2.17±0.10 andτT=1.80±0.10, βT=1.46±0.10.This self-organized critical model belongs to the same universalityclass with the Oslo rice-pile model studied by K. Christensen et al.[Phys. Rev. Lett. 77 (1996) 107], a rice-pile model studied by L.A.N. Amaral et al. [Phys. Rev. E 54 (1996) 4512], and a simple deterministic self-organized critical model studied byM.S. Vieira [Phys. Rev. E 61 (2000) 6056].  相似文献   

17.
    
A systematic analysis of low-temperature magnetic phase diagrams of Ce compounds is performed in order to recognize the thermodynamic conditions to be fulfilled by those systems to reach a quantum critical regime or, alternatively, to identify other kinds of low-temperature behavior. Based on specific heat (C m ) and entropy results, three different types of phase diagrams are recognized: (i) with the entropy involved in the ordered phase (S MO) decreasing proportionally to the ordering temperature (T MO); (ii) those showing a transference of degrees of freedom from the ordered phase to a non-magnetic component, with their C m (T MO) jumps (ΔC m ) vanishing at finite temperature; and (iii) those ending at a critical point at finite temperature because their ΔC m do not decrease sufficiently with T MO, producing an entropy accumulation at low temperature.

Only those systems belonging to the first case, i.e. with S MO?→?0 as T MO?→?0, can be regarded as candidates for quantum critical behavior. Their magnetic phase boundaries deviate from the classical negative curvature below T?≈?2.5?K, denouncing monotonic misleading extrapolations down to T?=?0. Different characteristic concentrations are recognized and analyzed for Ce-ligand alloyed systems. In particular, a pre-critical region is identified where the nature of the magnetic transition undergoes significant modifications, with its ?C m /?T discontinuity strongly affected by the magnetic field and showing an increasing remnant entropy at T?→?0. Physical constraints arising from the third law at T?→?0 are discussed and recognized from experimental results.  相似文献   

18.
    
Because quantum critical systems are very sensitive to the variation of parameters around the quantum phase transition (QPT), quantum criticality has been presented as an efficient resource for metrology. In this paper, we address the issue whether the divergent feature of the inverted variance is realizable in the presence of noise when approaching the QPT. Taking the quantum Rabi model (QRM) as an example, we obtain the analytical result for the inverted variance with single-photon relaxation. We show that the inverted variance may be convergent in time due to the noise. Since the precision of the metrology is very sensitive to the noise, as a remedy, we propose squeezing the initial state to improve the precision under decoherence. In addition, we also investigate the criticality-based metrology under the influence of the two-photon relaxation. Strikingly, although the maximum inverted variance still manifests a power-law dependence on the energy gap, the exponent is positive and depends on the dimensionless coupling strength. This observation implies that the criticality may not enhance but weaken the precision in the presence of two-photon relaxation, due to the non-linearity introduced by the two-photon relaxation.  相似文献   

19.
A new approach to dissipative quantum systems modeled by a system plus environment Hamiltonian is presented. Using a continuous sequence of infinitesimal unitary transformations, the small quantum system is decoupled from its thermodynamically large environment. Dissipation enters through the observation that system observables generically decay completely into a different structure when the Hamiltonian is transformed into diagonal form. The method is particularly suited for studying low-temperature properties. This is demonstrated explicitly for the super-Ohmic spin-boson model.  相似文献   

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