We solve the spin-1 quantum Ising model with single-ion anisotropy by mapping it onto a series of segmented spin-1/2 transverse Ising chains, separated by the $S^z =0$ states called holes. A recursion formula is derived for the partition function to simplify the summation of hole configurations. This allows the thermodynamic quantities of this model to be rigorously determined in the thermodynamic limit. The low temperature behavior is governed by the interplay between the hole excitations and the fermionic excitations within each spin-1/2 Ising segment. The quantum critical fluctuations around the Ising critical point of the transverse Ising model are strongly suppressed by the hole excitations.
Effect of the Canting of Local Anisotropy Axes on Ground-State Properties of a Ferrimagnetic Chain with Regularly Alternating Ising and Heisenberg Spins
Several Ising-type magnetic van der Waals (vdW) materials exhibit stable magnetic ground states. Despite these clear experimental demonstrations, a complete theoretical and microscopic understanding of their magnetic anisotropy is still lacking. In particular, the validity limit of identifying their one-dimensional (1-D) Ising nature has remained uninvestigated in a quantitative way. Here we performed the complete mapping of magnetic anisotropy for a prototypical Ising vdW magnet FePS$_3$ for the first time. Combining torque magnetometry measurements with their magnetostatic model analysis and…
Thermodynamic Measurement of Angular Anisotropy at the Hidden Order Transition of URu$_2$Si$_2$
重费米子化合物URu $_2$ Si $_2$由于其在17.5K以下形成的未知的隐藏有序而继续吸引着人们的极大兴趣。自旋涨落和低温准粒子的独特的伊辛性质是公认的。我们提出了详细的测量的角度各向异性的非线性磁化，揭示了$\cos^4 θ$伊辛各向异性在和以上的顺序过渡。利用Landau理论，我们证明了这隐含着巡游隐序参量的强Ising特征.
Ising versus XY anisotropy in frustrated R$_{2}$Ti$_{2}$O$_7$ compounds as seen by polarized neutrons
用极化中子衍射方法研究了具有单轴（R=Ho，Tb）和平面（R=Er，Yb）各向异性的R $_{2}$ Ti $_{2}$ O $_7$烧绿石化合物的场致磁序。局域磁化率张量\{ $χ_\parallel,χ_\perp$ \}的确定提供了在顺磁相（2-270 K）的场诱导结构的通用描述，无论场值（1-7 T）和方向。比较热变化的$χ_\parallel$和$χ_\perp$与计算使用稀土晶体场表明，交换和偶极相互作用必须考虑。我们确定在每种情况下的分子场张量，并表明它可以是强各向异性的。
Pressure-induced ferromagnetism with strong Ising-type anisotropy in YbCu$_2$Si$_2$
我们报告直流磁性测量YbCu $_2$ Si $_2$在10 GPa以上的压力使用微型陶瓷砧室。YbCu $_2$ Si $_2$在8 GPa压力下发生了从非磁性相到磁性相的压力诱导相变。我们发现一个自发的直流磁化在压力诱导阶段高于9.4 GPa。测定了2.0K时铁磁转变温度Tc和自发磁矩m_0的压力依赖关系。宏观测量的m_0值不到穆斯堡尔实验的一半。这种差异可以归因于铁磁相和顺磁相之间的空间相分离。这种分离表明，压力引起的相边界之间的顺磁和铁磁状态是一阶的。此外，我们还研究了压致铁磁态的磁各向异性。压力对磁化强度的影响沿磁易$c$ -轴的磁场比沿硬$a$ -轴的磁场大得多。压力诱导相具有很强的Ising型单轴各向异性，与针对YbCu $_2$ Si $_2$提出的两种晶体电场（CEF）模型一致。
We consider the dimerized spin-1 $XXZ$ chain with single-ion anisotropy $D$. In absence of an explicit dimerization there are three phases: a large-$D$, an antiferromagnetically ordered and a Haldane phase. This phase structure persists up to a critical dimerization, above which the Haldane phase disappears. We show that for weak dimerization the phases are separated by Gaussian and Ising quantum phase transitions. One of the Ising transitions terminates in a critical point in the universality class of the dilute Ising model. We comment on the relevance of our results to experiments on quasi-o…
We study phase transitions in the two-dimensional Heisenberg model with the Dzyaloshinskii-Moriya interaction, the Ising anisotropy ($η$), and the dipolar interaction under zero and finite magnetic fields ($H$). For three typical strengths (zero, weak, and strong) of the dipolar interaction, we present the $H$-$η$ phase diagrams by estimating order parameters for skyrmion-lattice and helical phases and in-plane magnetization by using a Monte Carlo method with an $O(N)$ algorithm. We find in the phase diagrams three types of skyrmion-lattice phases, i.e., two square lattices and a triangular la…
Energy dependence of the spin excitation anisotropy in uniaxial-strained BaFe1.9Ni0.1As2
用非弹性中子散射研究了单轴应变电子掺杂铁磷属元素化物BaFe $_{1.9}$ Ni $_{0.1}$ As $_2$在最佳超导性（$T_c=20$ K）附近自旋激发各向异性的温度和能量依赖性.我们的工作是由在单轴压力下观察电子欠掺杂铁磷族化合物的顺磁四元相的面内电阻率各向异性激发的，这归因于自旋驱动的伊辛-伊辛态或轨道有序。在这里，我们表明，自旋激发各向异性，自旋驱动的伊辛-伊辛相的签名，存在的能量低于$\sim$ 60毫电子伏的单轴应变BaFe $_{1.9}$ Ni $_{0.1}$作为$_2$。由于该能量尺度比单轴应变Ba（Fe $_{1-x}$ Co $_x$）$_2$ As $_2$在最佳超导性附近的$d_{xz}$和$d_{yz}$带的能量分裂大得多，因此自旋Ising-Ising相关性可能是电阻率各向异性和相关电子自旋相关性的驱动力。
The honeycomb $K-Γ$ model is known to have both deconfined spin liquid and confined phases. We study here a confinement transition between the Kitaev spin liquid and a dimerized phase in the limit of strong bond anisotropy. By partially projecting out Majorana states we are able to map the model onto a model of weakly coupled Ising chains in a transverse field. Within this mapping the ordered Ising phase corresponds to the condensation of $Z_2$ fluxes, or confinement. Our results may improve our understanding of the extensively studied spin liquid candidate material $α$-RuCl$_3$, where $K-Γ$ i…
Taking the Ising chain as a reference model we have derived a perturbative expression for the free energy density of the Heisenberg-Ising chain with strong easy-axis anisotropy. All calculations are performed on the ground of the Quantum Transfer Matrix approach. The obtained result agrees with the direct high-temperature expansion. It also agrees with the low-temperature cluster expansion in the special subregime when quantum fluctuations are weak against thermodynamical ones.
Exceptional Ising Magnetic Behavior of Itinerant Spin-polarized Carriers in URu2Si2
电子结构计算的基础上，我们表明，铀5 $f$磁矩在URu $_2$ Si $_2$表现出独特的伊辛行为，令人惊讶的是，来自巡回电子状态。分析了这种反常Ising行为的起因，认为是由于URu $_2$ Si $_2$具有特殊的近费米边嵌套电子结构，且具有较强的自旋-轨道相互作用.伊辛各向异性的理论适用于解释隐藏的顺序相在URu $_2$ Si $_2$相关的影响。
The $S=1$ bilinear-biquadratic Heisenberg exchange model on the triangular lattice with a single-ion anisotropy has previously been shown to host a number of exotic magnetic and nematic orders [Moreno-Cardoner $\textit{et al.}$, Phys. Rev. B $\textbf{90}$, 144409 (2014)], including an extensive region of "supersolid" order. In this work, we amend the model by an XXZ anisotropy in the exchange interactions. Tuning to the limit of an exactly solvable $S=1$ generalized Ising-/Blume-Capel-type model provides a controlled limit to access phases at finite transverse exchange. Notably, we find an add…
The $d=2$ critical Ising model is described by an exactly solvable Conformal Field Theory (CFT). The deformation to $d=2+ε$ is a relatively simple system at strong coupling outside of even dimensions. Using novel numerical and analytical conformal bootstrap methods in Lorentzian signature, we show that the leading corrections to the Ising data are more singular than $ε$. There must be infinitely many new states due to the $d$-dependence of conformal symmetry. The linear independence of conformal blocks is central to this bootstrap approach, which can be extended to more rigorous studies of non…
