Optical control of an individual Cr spin in a semiconductor quantum dot
Optical control of an individual Cr spin in a semiconductor quantum dot
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半导体量子点中单个 Cr 自旋的光学控制
DOI：
10.1088/1361-6641/ab13f5
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发表时间：
2019
影响因子：
1.9
通讯作者：
K. Makita
中科院分区：
文献类型：
--
作者：
L. Besombes;H. Boukari;V. Tiwari;A. Lafuente-Sampietro;S. Kuroda;K. Makita
半导体中的单个局域自旋在量子信息和量子增强传感等量子技术的框架中引起了极大的兴趣。结合在半导体中的磁性原子的局域自旋对于量子传感特别有前途。在这里，我们证明了在量子点（QD）中的Cr原子的自旋可以被光学控制，我们讨论了这个单自旋系统的主要性质。单个Cr掺杂量子点的光致发光和它们在磁场中的演化揭示了局部应变引起的Cr自旋的大的磁各向异性。这导致Cr自旋态的分裂和低能态Sz = 0和Sz =±1的热化。Cr掺杂量子点的磁光性质可以用一个有效的自旋哈密顿量来模拟，该哈密顿量考虑了量子点的自旋-应变耦合以及量子点对称性的影响。我们还表明，一个单一的Cr自旋可以通过共振光泵浦制备。在此过程中监测量子点的共振荧光强度允许探测自旋的光学初始化的动力学。由空穴-Cr交换相互作用和与声学声子的耦合的相互作用引起的空穴-Cr触发器是解释有效的共振光泵浦的弛豫的主要来源。Cr自旋弛豫时间在μs范围内测量。我们的证据表明，Cr自旋耦合到非平衡声学声子在内部或附近的量子点的光激发过程中产生的）。最后，我们证明了单个铬原子的任何自旋态的能量都可以通过光学斯塔克效应由共振单模激光独立调谐。所有这些特性使得Cr掺杂的量子点非常有希望用于发展混合自旋-机械系统，其中需要在振荡器中对单个自旋进行相干机械驱动。
Individual localized spins in semiconductors are attracting significant interest in the frame of quantum technologies including quantum information and quantum enhanced sensing. Localized spins of magnetic atoms incorporated in a semiconductor are particularly promising for quantum sensing. Here we demonstrate that the spin of a Cr atom in a quantum dot (QD) can be controlled optically and we discuss the main properties of this single spin system. The photoluminescence of individual Cr-doped QDs and their evolution in magnetic field reveal a large magnetic anisotropy of the Cr spin induced by local strain. This results in a splitting of the Cr spin states and in a thermalization on the lower energy states states S z= 0 and S z=±1. The magneto-optical properties of Cr-doped QDs can be modeled by an effective spin Hamiltonian including the spin to strain coupling and the influence of the QD symmetry. We also show that a single Cr spin can be prepared by resonant optical pumping. Monitoring the intensity of the resonant fluorescence of the QD during this process permits to probe the dynamics of the optical initialization of the spin. Hole-Cr flip-flops induced by an interplay of the hole-Cr exchange interaction and the coupling with acoustic phonons are the main source of relaxation that explains the efficient resonant optical pumping. The Cr spin relaxation time is measured in the μs range. We evidence that a Cr spin couples to non-equilibrium acoustic phonons generated during the optical excitation inside or near the QD). Finally we show that the energy of any spin state of an individual Cr atom can be independently tuned by a resonant single mode laser through the optical Stark effect. All these properties make Cr-doped QDs very promising for the development of hybrid spin-mechanical systems where a coherent mechanical driving of an individual spin in an oscillator is required.