Cryogenic Lorentz TEM study of a Berezinskii Kosterlitz Thouless phase transition in the quasi-two-dimensional ferromagnet K2CuF4
Cryogenic Lorentz TEM study of a Berezinskii Kosterlitz Thouless phase transition in the quasi-two-dimensional ferromagnet K2CuF4
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准二维铁磁体 K2CuF4 中 Berezinskii Kosterlitz Thouless 相变的低温洛伦兹 TEM 研究
DOI：
10.1017/s1431927621003548
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发表时间：
2021
影响因子：
2.8
通讯作者：
Akimitsu Jun
中科院分区：
文献类型：
--
作者：
Togawa Yoshihiko;Akashi Tetsuya;Kasai Hiroto;Paterson Gary;McVitie Stephen;Kousaka Yusuke;Shinada Hiroyuki;Kishine Jun-ichiro;Akimitsu Jun
系统的维数对其结构和动力学有很大的影响。事实上，低维系统中相变的性质已经引起了人们几十年的极大兴趣。该领域的一个著名工作是由Kosterlitz和Kosterless [1]提出的二维自旋系统的拓扑基态的建议，并获得了2016年的诺贝尔物理学奖。已经确定的是，在有限温度下，海森堡和XY自旋的一维和二维中不存在有序相和自发磁化，而磁化率的发散可以在有限温度下发生，作为海森堡自旋的2D系统中的相变的指示。这个令人困惑的局面被科斯特里茨和雷德莱斯解决了。他们表明，相变发生在TKT给定的有限温度下，其中准长程有序通过涡旋-反涡旋对的形成和解除束缚出现在XY自旋的2D系统中。Berezinskii独立地指出了XY模型中涡旋激发的重要性。二维XY模型使磁涡旋和反涡旋激发，并经历涡旋和反涡旋解束缚的相变，称为BKT相变。
The dimensionality of a system has a strong influence on its structure and dynamics. Indeed, the nature of the phase transition in a low-dimensional system has attracted considerable interest for many decades. One of the celebrated works in the field is the proposal of the topological ground state in the twodimensional (2D) spin system, which was made by Kosterlitz and Thouless [1] and awarded the Nobel Prize in Physics 2016.It is well established that no ordered phase and no spontaneous magnetization appear at a finite temperature in one and two dimensions of Heisenberg and XY spins, while a divergence of susceptibility may occur at a finite temperature as an indication of the phase transition in the 2D system of Heisenberg spins. This puzzling situation was resolved by Kosterlitz and Thouless. They showed that the phase transition occurs at a finite temperature given by TKT where quasi long-range order emerges in the 2D system of XY spins through the formation and unbinding of vortex–antivortex pairs. Berezinskii independently pointed out the importance of vortex excitations in the XY model. The 2D XY model enables magnetic vortex and antivortex excitations and undergoes a phase transition of vortex and antivortex unbinding, referred to as BKT phase transition.