Yar Abdullah, Taif Usman Muhammad, Sabeeh Kashif
Department of Physics, Kohat University of Science and Technology, Kohat 26000, Khyber Pakhtunkhwa, Pakistan.
Department of Physics, Quaid-i-Azam University, Islamabad 45320, Pakistan.
J Phys Condens Matter. 2023 Aug 8;35(44). doi: 10.1088/1361-648X/acebaa.
We investigate the spin tunability of Dirac fermions on the surface of a 3D topological insulator in proximity to a helical spin density wave, acting as an applied one-dimensional periodic potential for spins produced by spiral multiferroic oxide. It is observed that the spin mean values of Dirac fermion undergo oscillations under the influence of such a periodic potential created by the exchange field of magnetization. The tunability of spin is strongly affected by the strength, orientation and period of the exchange field. In particular, the mean values of spin are anisotropic around the Dirac point, depending strongly on the amplitude and spatial period of the periodic potential. We also find that the spin expectation values change significantly by changing the plane of magnetization. Interestingly, the in-plane components of spin mean values perform pronounced oscillations, whereas the out of plane component does not oscillate at all. The oscillations of planar components of spin are originated from the spin-momentum locking on the surface of topological insulator.
我们研究了三维拓扑绝缘体表面上的狄拉克费米子在靠近螺旋自旋密度波时的自旋可调性，螺旋自旋密度波作为由螺旋多铁氧化物产生的自旋的外加一维周期性势。观察到狄拉克费米子的自旋平均值在由磁化交换场产生的这种周期性势的影响下发生振荡。自旋的可调性受到交换场的强度、取向和周期的强烈影响。特别是，自旋平均值在狄拉克点周围是各向异性的，强烈依赖于周期性势的幅度和空间周期。我们还发现，通过改变磁化平面，自旋期望值会发生显著变化。有趣的是，自旋平均值的面内分量表现出明显的振荡，而面外分量根本不振荡。自旋平面分量的振荡源于拓扑绝缘体表面上的自旋-动量锁定。
