近日，浙江大学的郑毅&陆赟豪及其研究团队取得一项新进展。经过不懈努力，他们揭示范德华反铁磁体中具有可调谐自旋几何相位的量子隧穿。相关研究成果已于2024年10月22日在国际知名学术期刊《自然—物理学》上发表。
本研究在多层范德华反铁磁体CrPS4中展示了具有可调自旋几何相位的量子隧穿现象。电子隧穿的自旋几何相位由磁场依赖的变磁性相变所控制。CrPS4单层的方形晶格导致传导带最小值附近出现强烈的t2g轨道离域化。
这产生了一个一维自旋系统，其中t2g和eg自旋通道之间的能量顺序发生逆转，这既阻止了通过集体磁振子激发的层内自旋弛豫，也阻止了t2g和eg自旋通道之间的层间自旋跳跃。由此产生的相干电子传输显示出显著的隧穿磁阻振荡，这体现了单个电子布洛赫波在时间反演对称隧穿回路中周期性量子演化的量子干涉。
这项研究结果表明，源于贝里相位非绝热推广的阿哈罗诺夫-安南丹相位的出现。
据悉，电子在固体中的隧穿效应作为一种基本的量子现象，为多种现代技术奠定了基础。范德华磁体的出现为研究非常规隧穿现象提供了新的契机。
附：英文原文
Title: Quantum tunnelling with tunable spin geometric phases in van der Waals antiferromagnets
Author: Cheng, Man, Hu, Qifeng, Huang, Yuqiang, Ding, Chenyang, Qiang, Xiao-Bin, Hua, Chenqiang, Fang, Hanyan, Lu, Jiong, Peng, Yuxuan, Yang, Jinbo, Xi, Chuanying, Pi, Li, Watanabe, Kenji, Taniguchi, Takashi, Lu, Hai-Zhou, Novoselov, Kostya S., Lu, Yunhao, Zheng, Yi
Issue&Volume: 2024-10-22
Abstract: Electron tunnelling in solids, a fundamental quantum phenomenon, lays the foundation for various modern technologies. The emergence of van der Waals magnets presents opportunities for discovering unconventional tunnelling phenomena. Here, we demonstrate quantum tunnelling with tunable spin geometric phases in a multilayer van der Waals antiferromagnet CrPS4. The spin geometric phase of electron tunnelling is controlled by magnetic-field-dependent metamagnetic phase transitions. The square lattice of a CrPS4 monolayer causes strong t2g-orbital delocalization near the conduction band minimum. This creates a one-dimensional spin system with reversed energy ordering between the t2g and eg spin channels, which prohibits both intralayer spin relaxation by means of collective magnon excitations and interlayer spin hopping between the t2g and eg spin channels. The resulting coherent electron transmission shows pronounced tunnel magnetoresistance oscillations, manifesting quantum interference of cyclic quantum evolutions of individual electron Bloch waves by means of the time-reversal symmetrical tunnelling loops. Our results suggest the appearance of Aharonov–Anandan phases that originate from the non-adiabatic generalization of the Berry’s phase.
DOI: 10.1038/s41567-024-02675-x
Source: https://www.nature.com/articles/s41567-024-02675-x