Temperature dependence of the $(\pi,0)$ anomaly in the excitation spectrum of the 2D quantum Heisenberg antiferromagnet
Temperature dependence of the $(\pi,0)$ anomaly in the excitation spectrum of the 2D quantum Heisenberg antiferromagnet
复制标题
二维量子海森堡反铁磁体激发光谱中 $(pi,0)$ 异常的温度依赖性
DOI：
10.1088/1361-648x/ab757a
复制
发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Rønnow, H M
中科院分区：
文献类型：
--
作者：
Wan, W;Christensen, N B;Sandvik, A W;Tregenna-Piggott, P;Nilsen, G J;Mourigal, M;Perring, T G;Frost, C D;McMorrow, D F;Rønnow, H M
在低温极限下，方形晶格上的二维量子海森堡反铁磁体（2DQHAFSL）在区域边界的短波长处表现出光谱异常。在这一点附近，一磁振子响应中的极点表现出向下色散，受到严重的阻尼和衰减，让位于向高能量延伸的各向同性连续激发。异常的起源和连续体的存在是目前理论界的兴趣所在，人们认为后者证明了二维系统中自旋的存在。本文介绍了金属有机化合物Cu (DCOO) d2o （CFTD）的中子非弹性散射实验和量子蒙特卡罗计算结果，这是2DQHAFSL的一个很好的物理实现，旨在研究异常如何演变到有限温度。我们的数据表明，在变暖的情况下，这种异常现象在长程三维秩序的丧失中幸存下来，因此它是二维系统的一个强大特征。随着温度的进一步升高，带边界响应逐渐变软、变宽，将异常冲掉。我们的数据与有限温度量子蒙特卡罗模拟结果的比较证实了这一点，两者非常吻合。在反铁磁区中心附近，在所研究的温度范围内，磁激励没有明显的软化。
It is well established that in the low-temperature limit, the two-dimensional quantum Heisenberg antiferromagnet on a square lattice (2DQHAFSL) exhibits an anomaly in its spectrum at short-wavelengths on the zone-boundary. In the vicinity of the point the pole in the one-magnon response exhibits a downward dispersion, is heavily damped and attenuated, giving way to an isotropic continuum of excitations extending to high energies. The origin of the anomaly and the presence of the continuum are of current theoretical interest, with suggestions focused around the idea that the latter evidences the existence of spinons in a two-dimensional system. Here we present the results of neutron inelastic scattering experiments and Quantum Monte Carlo calculations on the metallo-organic compound Cu (DCOO) D 2 O (CFTD), an excellent physical realisation of the 2DQHAFSL, designed to investigate how the anomaly at evolves up to finite temperatures. Our data reveal that on warming the anomaly survives the loss of long-range, three-dimensional order, and that it is thus a robust feature of the two-dimensional system. With further increase of temperature the zone-boundary response gradually softens and broadens, washing out the anomaly. This is confirmed by a comparison of our data with the results of finite-temperature Quantum Monte Carlo simulations where the two are found to be in good accord. In the vicinity of the antiferromagnetic zone centre, there was no significant softening of the magnetic excitations over the range of temperatures investigated.