Thakur Tanmay, Szafran Bartłomiej
Faculty of Physics and Applied Computer Science, AGH University of Krakow, al. Mickiewicza 30, 30-059, Kraków, Poland.
Sci Rep. 2023 Nov 1;13(1):18796. doi: 10.1038/s41598-023-45860-3.
We consider an array of four quantum dots defined in phosphorene containing three excess electrons, i.e., in the conditions of near half filling when itinerant Nagaoka ferromagnetism is expected to appear in a square array with isotropic interdot hopping. The interdot hopping in the array arranged in a square inherits the anisotropy from the form of the phosphorene conduction band. We apply the configuration interaction method for discussion of the appearance and stability of the spin-polarized ground state and discuss the compensation of the effective mass anisotropy by the geometry of the quantum dot array. Our study shows strong stability of Nagaoka ferromagnetism for optimized geometry of the array, with the Nagaoka gap as large as ∼ 230 µeV. A phase diagram for the ground-state spin ordering versus the geometric parameters of the array is presented. We study the suppression of the ferromagnetism in a transition of the [Formula: see text] array to a quasi-1D chain and indicate that the shift of one of the quantum dots away from the array center is enough to transform the system to a quantum dot chain. A shift in the zigzag crystal direction induces the low-spin ground state more effectively than a shift along the armchair direction. We also discuss the robustness of the spin ordering against detuning one of the dots. The ferromagnetic ground-state survives as long as the detuning is not large enough to trap one of the electrons within a single quantum dot (for positive detuning) or remove one of the quantum dots of the accessible energy range (for negative detuning).
我们考虑在含三个多余电子的磷烯中定义的四个量子点阵列，即处于近半填充条件下，此时预计在具有各向同性点间跳跃的方形阵列中会出现巡游型永冈铁磁性。方形排列的阵列中的点间跳跃继承了磷烯导带形式的各向异性。我们应用组态相互作用方法来讨论自旋极化基态的出现和稳定性，并讨论量子点阵列的几何形状对有效质量各向异性的补偿。我们的研究表明，对于优化的阵列几何形状，永冈铁磁性具有很强的稳定性，永冈能隙高达约230微电子伏特。给出了基态自旋序相对于阵列几何参数的相图。我们研究了从[公式：见原文]阵列到准一维链的转变中铁磁性的抑制，并指出将其中一个量子点从阵列中心移开足以将系统转变为量子点链。沿锯齿形晶体方向的位移比沿扶手椅方向的位移更有效地诱导低自旋基态。我们还讨论了自旋序对其中一个量子点失谐的鲁棒性。只要失谐程度不足以将其中一个电子捕获在单个量子点内（对于正失谐）或移除可及能量范围内的一个量子点（对于负失谐），铁磁基态就会存在。
