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中国物理学会期刊

光辐照蜂窝状基塔耶夫-海森堡铁磁体中的相互作用弗洛凯拓扑磁子

Interacting Floquet topological magnons in light-irradiated honeycomb Kitaev-Heisenberg ferromagnets with Dzyaloshinskii-Moriya interaction

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  • 近年来,基塔耶夫材料因其独特的物理性质受到了越来越多研究者的关注。在真实的二维铁磁材料中,基塔耶夫相互作用常伴随Dzyaloshinskii-Moriya (DM)相互作用。本文在平均场近似下,发展了适用于二维蜂窝状基塔耶夫-海森堡铁磁体的自洽重整化自旋波理论。主要研究了含DM相互作用的二维蜂窝状基塔耶夫-海森堡铁磁体在激光辐照下,由磁子间相互作用引起的重整化效应。重点分析了不同光强下温度和磁场对能带结构及拓扑相的影响。研究结果表明,在一定的光强范围内,适当增强光强可降低带隙闭合所对应的临界温度Tc,但同时会提高该过程中所需的临界磁场强度hc。通过对临界点Tc (hc)两侧磁子能带的陈数进行数值计算,可确认拓扑相变的发生以狄拉克点处的磁子能隙闭合为特征,且该相变发生在热力学稳定区域内。此外,这类相变可通过改变温度或调节磁场加以诱导,并伴随热霍尔系数的符号反转。该现象可作为实验探测拓扑相变发生的重要指标。

     

    In recent years, Kitaev materials have garnered significant attention for their unique physical properties. While light-field manipulation of magnonic topological states in realistic two-dimensional ferromagnetic systems has been extensively explored theoretically, existing studies remain largely confined to zero-temperature or static limits. Consequently, several critical issues remain unresolved: the dynamic mechanisms of magnonic gap closing and reopening in light-driven ferromagnets at finite temperatures below the Curie point; the quantitative validation of thermal Hall conductivity as a criterion for topological phase transitions; and the differential impacts of light irradiation on the critical points of temperature- versus magnetic-field-induced topological phase transitions. To address these challenges, we develop a self-consistent renormalized spin-wave theory within the mean-field approximation for a two-dimensional honeycomb Kitaev-Heisenberg ferromagnet with Dzyaloshinskii-Moriya interaction. We systematically investigate the renormalization effects arising from magnon-magnon interactions under laser irradiation. Our key findings are threefold. First, we reveal a reversible, light-controlled magnonic bandgap tuning mechanism at finite temperatures. We demonstrate that, under specific light intensities and below the Curie temperature, the magnonic bandgap can be closed and reopened solely by adjusting temperature or magnetic field. This finding overcomes the limitations of previous studies restricted to zero-temperature photoinduced topological phase transitions. Second, we establish the sign reversal of thermal Hall conductivity as a reliable experimental signature of topological phase transitions. Numerical calculations of the Chern numbers across the critical point confirm that the topological phase transition is characterized by magnonic bandgap closure at the Dirac point within the thermodynamically stable region. Crucially, the jump in the Chern number strictly corresponds to the anomalous variation in thermal Hall conductivity.Third, we uncover a novel asymmetric evolution of the topological phase diagram induced by light irradiation. Increasing light intensity synchronously reduces both the critical temperature (Tc) for temperature-induced topological phase transitions and the Curie temperature, while significantly increasing the critical magnetic field (hc), for magnetic-field-induced transitions. This previously unreported asymmetry elucidates the distinct influence mechanisms of temperature and magnetic field on band structures under varying light intensities and provides new insights into the selective control of topological phase transition pathways via light fields. Notably, the accompanying sign reversal of thermal Hall conductivity serves as a vital indicator for the experimental detection of these topological phase transitions.

     

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