共查询到20条相似文献,搜索用时 31 毫秒
1.
Prosen T 《Physical review letters》2011,106(21):217206
An explicit matrix product ansatz is presented, in the first two orders in the (weak) coupling parameter, for the nonequilibrium steady state of the homogeneous, nearest neighbor Heisenberg XXZ spin 1/2 chain driven by Lindblad operators which act only at the edges of the chain. The first order of the density operator becomes, in the thermodynamic limit, an exact pseudolocal conservation law and yields-via the Mazur inequality-a rigorous lower bound on the high-temperature spin Drude weight. Such a Mazur bound is a nonvanishing fractal function of the anisotropy parameter Δ for |Δ|<1. 相似文献
2.
Alexander O. Gogolin Alexander A. Nersesyan Alexei M. Tsvelik Lu Yu 《Nuclear Physics B》1999,540(3):277-730
The influence of non-magnetic doping on the thermodynamic properties of two-leg S = 1/2 spin ladders is studied in this paper. It is shown that, for a weak interchain coupling, the problem can be mapped onto a model of random mass Dirac (Majorana) fermions. We investigate in detail the structure of the fermionic states localized at an individual mass kink (zero-modes) in the framework of a generalized Dirac model. The low-temperature thermodynamic properties are dominated by these zero-modes. We use the single-fermion density of states, known to exhibit the Dyson singularity in the zero-energy limit, to construct the thermodynamics of the spin ladder. In particular, we find that the magnetic susceptibility χ diverges at T → 0 as 1/T ln2(1/T), and the specific heat behaves as C 1/ln3(1/T). The predictions on magnetic susceptibility are consistent with the most recent results of quantum Monte Carlo simulations on doped ladders with randomly distributed impurities. We also calculate the average staggered magnetic susceptibility induced in the system by such defects. 相似文献
3.
We investigate the doping of a two-orbital chain with mobile S = 1/2 fermions as a valid model for Y2-xCaxBaNiO5. The S = 1 spins are stabilized by strong, ferromagnetic Hund's rule couplings. We calculate correlation functions and thermodynamic quantities by density matrix renormalization group methods and find a new hierarchy of energy scales in the spin sector upon doping. Gapless spin excitations are generated at a lower energy scale by interactions among itinerant polarons created by each hole and coexist with the larger scale of the gapful spin-liquid background of the S = 1 chain accompanied by a finite string order parameter. 相似文献
4.
Effects of magnetic frustration in the model of nine-membered antiferromagnetic s = 3/2 molecular spin ring are investigated. We use a Heisenberg spin model with nearest-neighbor interactions, single-ion
anisotropy and with tunable bond defect leading to continuously varying topology: from closed to open ring. In order to identify
a frustrated phase we calculate the full energy spectrum of the model and a number of thermodynamic quantities at low temperature.
The calculations are performed by means of numerically exact methods: quantum transfer matrix and exact diagonalization. It
is shown that total and local magnetizations, nearest-neighbor spin correlations and spin fluctuations can serve as consistent
frustration signatures. Magnetizations and spin-spin correlations are reduced in the frustrated phase whereas fluctuations
and correlations of fluctuations increase. The ground state in a frustrated phase is a m = 1/2 doublet and in the non-frustrated phase a m = 3/2 doublet. In the system studied bipartiteness is not opposite to frustration as there are regions in the parameter space
for which the system is neither bipartite nor frustrated. 相似文献
5.
Guo-Ping Li Zhong-Wen Feng Hui-Ling Li Xiao-Tao Zu 《The European Physical Journal C - Particles and Fields》2017,77(4):250
In curved space-time, the Hamilton–Jacobi equation is a semi-classical particle equation of motion, which plays an important role in the research of black hole physics. In this paper, starting from the Dirac equation of spin 1/2 fermions and the Rarita–Schwinger equation of spin 3/2 fermions, respectively, we derive a Hamilton–Jacobi equation for the non-stationary spherically symmetric gravitational field background. Furthermore, the quantum tunneling of a charged spherically symmetric Kinnersly black hole is investigated by using the Hamilton–Jacobi equation. The result shows that the Hamilton–Jacobi equation is helpful to understand the thermodynamic properties and the radiation characteristics of a black hole. 相似文献
6.
S. I. Doronin A. N. Pyrkov E. B. Fel’dman 《Journal of Experimental and Theoretical Physics》2007,105(5):953-961
We investigate entanglement of spin pairs in alternating open spin chains (s = 1/2) with spin-spin interactions (SSI) in the thermodynamic equilibrium state in an external magnetic field. The reduced density matrix of an arbitrarily chosen spin pair was calculated. The entanglement of a spin pair was evaluated with the Wootters criterion. The temperature at which the entangled state arises in the chosen pair was determined. Entanglement (concurrence) is shown to oscillate as a function of the position of a spin pair in the chain. The results demonstrate the dependence of the entanglement in arbitrarily chosen pairs of neighboring spins on the temperature, the position of the spin pair in the chain, chain length, and the ratio between the SSI constants. Qualitative explanation of these dependences is offered. The role of the terminal spins in the generation of entanglement is explained. 相似文献
7.
8.
Helton JS Matan K Shores MP Nytko EA Bartlett BM Yoshida Y Takano Y Suslov A Qiu Y Chung JH Nocera DG Lee YS 《Physical review letters》2007,98(10):107204
We have performed thermodynamic and neutron scattering measurements on the S=1/2 kagomé lattice antiferromagnet ZnCu3(OH)6Cl2. The susceptibility indicates a Curie-Weiss temperature of theta CW approximately = -300 K; however, no magnetic order is observed down to 50 mK. Inelastic neutron scattering reveals a spectrum of low energy spin excitations with no observable gap down to 0.1 meV. The specific heat at low-T follows a power law temperature dependence. These results suggest that an unusual spin liquid state with essentially gapless excitations is realized in this kagomé lattice system. 相似文献
9.
We employ a thermodynamic integration method (TIM) to establish the values of the residual entropy for the geometrically frustrated spin-s triangular Ising antiferromagnet, with the spin values s = 1/2, 1, 3/2, 2 and 5/2. The case of s = 1/2, for which the exact value is known, is used to assess the TIM performance. We also obtain an analytical formula for the lower bound in a general spin-s model and conjecture that it should reasonably approximate the true residual entropy for sufficiently large s. Implications of the present results in relation to reliability of the TIM as an indirect method for calculating global thermodynamic quantities, such as the free energy and the entropy, in similar systems involving frustration and/or higher spin values by standard Monte Carlo sampling are briefly discussed. 相似文献
10.
Entanglement is studied in an open alternating chain of nuclear spins s = 1/2 with spin-spin couplings in an external magnetic field under the thermodynamic equilibrium conditions. A reduced density matrix has been calculated for an arbitrarily chosen spin pair. The entanglement of the spin pair has been estimated according to the Wootters criterion. The temperature at which an entangled state appears in a chosen pair has been determined. It has been shown that the numerical characteristics of the entanglement are oscillating functions of the position of the spin pair in the chain. 相似文献
11.
The one-dimensional spin-1/2 ferromagnetic and antiferromagnetic chains with anisotropic coupling are studied within the Green's function theory in both planar and uniaxial regimes. The spin Green's functions are decoupled at a stage one-step further than the Tyablikov's decoupling under the constraint 2>= 0. The behaviors of the correlation functions are studied in the entire temperature regime. The thermodynamic properties are also discussed, and the result is consistent with the numerical simulation. 相似文献
12.
本文采用与文献[1]完全相类似的方法作出一般化Ising模型s=1在面心立方格子(fcc)上最近邻相互作用的反铁磁系统的统计理论,即用Pad近似式处理配分函数的高、低温幂级数有限项展开式,得出其反铁磁-顺磁转变为一阶相变。Tc=1.33J/k,小于(1/2)相应的相变点。文中算出了相关的热力学量如内能、潜热、熵、比热、长程和短程序参量,以及磁化率等。值得指出的是:(1)fcc上反铁磁-顺磁相变属于一阶,这是由格子密堆积的拓扑特征所决定,与s的大小无关;(2)Tc(s)随s的增加而缓慢地下降。
关键词: 相似文献
13.
X. Wang 《Annals of Physics》2007,322(9):2168-2178
For sufficiently large but finite N independent spin-1/2 paramagnets in a constant magnetic field, the orientation of every spin has the same probability to be parallel or anti-parallel to that of the magnetic field. In our statistical ensemble treatment, all fundamental thermodynamic quantities fluctuate, including the entropy and temperature, and all fluctuations are gradually vanishing as the temperature itself approaches zero. Our approach presents a remedy of infinite temperature fluctuations and reproduces other reasonable results that are given by standard theory. 相似文献
14.
Maliheh Amiri Hossein Akbari Bashir Nedaee-shakarab Arash Boochani Amin Aminian Yousof Zangeneh Sirvan Naderi 《理论物理通讯》2019,71(4):455-462
The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the ?lms thermodynamic stability of the [001] direction in four cases including:Sc-Sc, Sc-Co, Sc-Si and Co-Si terminations are studied using the ?rst principles calculations(FPLAPW) within the framework of the density functional theory(DFT). The band structure calculations represent the ferromagnetic halfmetallic properties with 100% spin polarization and 0.54 e V indirect gap in spin down for Sc2 CoSi bulk with optimized lattice parameters of 6.25 A?. The total magnetic moment obtained for this compound is-1.0 μB, which is in accordance with Slater-Pauling rule. The half-metallic(HM) behavior by 100% spin polarization at Fermi level is occurred in the Sc-Si termination with a 0.32 eV gap in down spin. The optical responses have been calculated for the bulk and ScSi termination by a red shift in these parameters and the metallic treatments have been increased. According to the thermodynamic phase diagrams, it is shown the Sc-Si and Sc-Sc terminations are more stable than other terminations. 相似文献
15.
Thermodynamic properties of the spin-1/2 ferromagnetic Heisenberg chain with long-range interactions
The one-dimensional spin-1/2 XYZ ferromagnetic model in a transverse field and uniform long-range interactions among the z components of the spins is studied using the mean-field Jordan–Wigner transformation. The thermodynamic quantities results like Helmholtz free energy, the internal energy, the specific heat and the isothermal susceptibility are obtained both analytically and numerically. The phase transition of the system at a finite temperature is also discussed. Our results agree with numerical results of the XYZ spin chain by others. 相似文献
16.
研究了以带有Dzyaloshinski-Mariya(DM)相互作用的两比特自旋体系为工质的量子纠缠Otto热机和量子Stirling热机.两种不同热机在各自的循环过程中,通过保持其他参量不变,只有DM相互作用发生改变,从而分析热机循环中DM相互作用与热传递、做功以及效率等热力学量之间的关系.研究结果表明:DM相互作用对两种热机的基本量子热力学量都具有重要的影响,但量子Stirling热机由于回热器的使用,其循环效率会大于量子Otto纠缠热机的效率,甚至会超过Carnot效率;得到了量子Otto纠缠热机和量子Stirling热机做正功的条件.因此,在这两个纠缠体系中,热力学第二定律都依然成立. 相似文献
17.
A complete dimerized state exists for one kind of two-leg spin half ladders, which has local antiferromagnetic ordering and
frustration effect at the same time. The system’s low-lying excitations can be obtained exactly which enables us to calculate
thermodynamic quantities such as specific heat and magnetic susceptibility at low temperatures. Our results also show that
the subset energy spectrum is a good approximation to the whole spectrum even for the usual two-leg spin half ladder without
frustration. 相似文献
18.
The thermodynamic quantities for the gases of massless particles
with spin s = 1 / 2, 1, 3 / 2, 2 around static spherical black
holes are investigated by using the brick-wall method. The
appearance of the spin-dependent subleading terms is demonstrated
and the terms are shown to contain not only the linear and quadratic
terms of the spins but also a zero-power term of the spins. 相似文献
19.
Hoi Yin SHIK 《Frontiers of Physics》2010,5(2):188
A complete dimerized state exists for one kind of two-leg spin half ladders, which has local antiferromagnetic ordering and frustration effect at the same time. The system’s low-lying excitations can be obtained exactly which enables us to calculate thermodynamic quantities such as specific heat and magnetic susceptibility at low temperatures. Our results also show that the subset energy spectrum is a good approximation to the whole spectrum even for the usual two-leg spin half ladder without frustration. 相似文献
20.
We describe a low-temperature thermodynamic model for dynamic nuclear polarization (DNP) via continuous-wave partial saturation of electron spin resonance (ESR) lines that are both homogeneously and inhomogeneously broadened. It is a variant of a reasoning proposed by Borghini, which in turn used Redfield’s thermodynamic treatment of saturation. Our variant is furthermore based on Provotorov’s insight that under partial saturation of a coupled-spin system two distinct spin temperatures should appear in a thermodynamical theory. We apply our model to DNP results obtained at a temperature of 1.2?K and in magnetic fields of 3.35 and 5?T on 1-13C labeled sodium acetate dissolved in a frozen D2O/ethanol-d6 solution doped with the free radical TEMPO. 相似文献