[论文解读] Observation of spin polarons in a frustrated moiré Hubbard system

Zui Tao, Wenjin Zhao+6 more|arXiv (Cornell University)|Jul 23, 2023

Physics of Superconductivity and Magnetism被引用 8

一句话总结

论文报道在三角格点莫尔-Hubbard 系统中自旋极化子的实验观测，鉴定出自旋极化子相并表征其自旋与结合能。

ABSTRACT

The electron's kinetic energy plays a pivotal role in magnetism. While virtual electron hopping promotes antiferromagnetism in an insulator, the real process usually favors ferromagnetism. But in kinetically frustrated systems, such as hole doped triangular lattice Mott insulators, real hopping has been shown to favor antiferromagnetism. Kinetic frustration has also been predicted to induce a new quasiparticle -- a bound state of the doped hole and a spin flip called a spin polaron -- at intermediate magnetic fields, which could form an unusual metallic state. However, the direct experimental observation of spin polarons has remained elusive. Here we report the observation of spin polarons in triangular lattice MoTe2/WSe2 moiré bilayers by the reflective magnetic circular dichroism measurements. We identify a spin polaron phase at lattice filling factor between 0.8-1 and magnetic field between 2-4 T; it is separated from the fully spin polarized phase by a metamagnetic transition. We determine that the spin polaron is a spin-3/2 particle and its binding energy is commensurate to the kinetic hopping energy. Our results open the door for exploring spin polaron pseudogap metals, spin polaron pairing and other new phenomena in triangular lattice moiré materials.

研究动机与目标

• 在惯性受限的系统中驱动动能的磁性研究的动机。
• 证明在三角格点莫尔-Hubbard 系统中存在自旋极化子准粒子。
• 表征自旋极化子态的自旋、结合能与相边界。
• 探索对自旋极化子伽马能隙金属及相关现象的潜在影响。

提出的方法

• 使用反射磁圆偏振分光来探测三角格点莫尔双层中的自旋与电荷动力学。
• 调节晶格充填因子与磁场，以绘制0.8–1充填与2–4 T场之间的相行为。
• 鉴定一个自旋极化子相及将其与完全自旋极化相分隔开的亚磁变/磁变边界。
• 确定极化子的自旋为自旋-3/2，并将其结合能与动跃能进行比较。

实验结果

研究问题

• RQ1 在惯性受限莫尔-Hubbard 系统中是否可以观测到自旋极化子？
• RQ2 在三角格点莫尔材料中，自旋极化子的自旋、结合能和相边界是什么？
• RQ3 自旋极化子相与亚磁变转变以及完全自旋极化态之间有何关系？

主要发现

• 在晶格充填0.8–1与磁场2–4 T时检测到自旋极化子相。
• 自旋极化子被鉴定为自旋-3/2准粒子。
• 自旋极化子的结合能与动跃能相当。
• 相边界通过亚磁变转变将自旋极化子态与完全自旋极化相分隔开。