Department of Physics, Jadavpur University, 188, Raja Subodh Chandra Mallick Rd, Jadavpur, Kolkata, West Bengal 700032, India.
J Phys Condens Matter. 2023 May 30;35(34). doi: 10.1088/1361-648X/accf56.
Very often the magnetic skyrmions (topologically protected spin textures) form a triangular crystal in chiral magnets. Here we study the effect of itinerant electrons on the structure of skyrmion crystal (SkX) on triangular lattice using Kondo lattice model in the large coupling limit and treating the localized spins as classical vectors. To simulate the system, we employ hybrid Markov Chain Monte Carlo method (hMCMC) which includes electron diagonalization in each MCMC update for classical spins. We present the low-temperature results for12×12system at electron densityn=1/3which show a sudden jump in skyrmion number reducing the size of the skyrmions when we increase the hopping strength of the itinerant electrons. We find that this high skyrmion number SkX phase is stabilized by a combined effect: lowering of density of states at electron fillingn=1/3and also pushing the bottom energy states further down. We show that these results hold for larger24×24system using traveling cluster variation of hMCMC. We expect that itinerant triangular magnets might exhibit the possible transition between low-density to high-density SkX phases by applying external pressure.
通常情况下，磁 skyrmions（拓扑保护的自旋纹理）在手性磁体中形成三角形晶体。在这里，我们使用近藤晶格模型在大耦合极限下研究巡游电子对三角晶格上 skyrmion 晶体（SkX）结构的影响，并将局域自旋视为经典向量。为了模拟系统，我们采用了混合 Markov 链蒙特卡罗方法（hMCMC），其中包括在每个经典自旋的 MCMC 更新中进行电子对角化。我们给出了电子密度为 n=1/3 的 12×12 系统在低温下的结果，结果表明当我们增加巡游电子的跃迁强度时，skyrmion 的数量会突然减少，从而减小 skyrmion 的尺寸。我们发现，这种高 skyrmion 数 SkX 相是由多种因素共同稳定的：在电子填充 n=1/3 时降低态密度，同时也将底部的能态进一步向下推。我们使用 hMCMC 的旅行团变分法证明了这些结果对于更大的 24×24 系统也是成立的。我们预计，通过施加外部压力，巡游三角磁体可能会在低密度和高密度 SkX 相之间发生可能的转变。
