极紫外辐照下钙钛矿超快相变中的瞬态铁磁性：SrTiO3与KTaO3的对比研究
Transient Ferromagnetism in Ultrafast Phase Transitions in Perovskites under XUV Irradiation: A Comparative Study of SrTiO3 and KTaO3
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中文总结 AI 辅助
本研究用XTANT3多尺度代码对比STO与KTO在XUV辐照下的超快相变，发现STO因Ti 3d轨道会产生瞬态铁磁性，KTO因Ta 5d轨道保持顺磁性，还明确了极性势阱加深的应变放大效应，为钙钛矿光电器件的超快光学调控提供依据。
中文摘要 AI 辅助
本研究采用XTANT3多尺度代码，探究钛酸锶（SrTiO3，STO）和钽酸钾（KTaO3，KTO）对强飞秒辐照的超快结构与电子响应。研究发现，在STO的阈值剂量0.7 eV/atom、KTO的阈值剂量0.9 eV/atom下，会热形成超离子态，表现为氧子系统选择性熔化，而金属亚晶格保持有序；该状态持续至STO的1.6 eV/atom、KTO的1.5 eV/atom，超过此阈值则发生完全无序。对瞬态电子态密度的分析表明，B位d轨道决定两种材料的差异行为：STO中紧凑的Ti 3d轨道产生窄导带和大内交换参数，驱动1皮秒（ps）时间尺度上的瞬态铁磁不稳定性；而KTO中空间更延展的Ta 5d轨道产生更宽的导带和更小的交换参数，使KTO保持顺磁性。这些结果表明，d轨道空间延展度是影响相变序列及极端电子激发下磁响应的结构参数，对基于钙钛矿的光电器件中电子与磁性质的超快光学调控具有重要意义。朗道-德文希尔（Landau Devonshire）分析显示，0.3 eV/atom的辐照会使无应变及有应变STO、KTO的极性势阱瞬态加深，其中应变STO的效应较无应变情况放大约2倍，应变KTO则放大约6倍。
英文摘要
We study ultrafast structural and electronic responses of strontium titanate and potassium tantalate to intense femtosecond irradiation using the XTANT3 multiscale code. It is found that at threshold doses of 0.7 eVatom in STO and 0.9 eVatom in KTO, a superionic state thermally forms with selective melting of the oxygen subsystem while metallic sublattices remain ordered. This state persists up to 1.6 eVatom STO and 1.5 eVatom KTO, above which complete disorder occurs. Analysis of the transient electronic density of states suggests that the B site d orbitals govern the divergent behaviour of the two materials: the compact Ti 3d orbitals in STO produce a narrow conduction band and large intraatomic exchange parameter, driving a transient ferromagnetic instability on 1 ps timescales, whereas the more spatially extended Ta 5d orbitals in KTO yield a broader conduction band and smaller exchange parameter, keeping KTO paramagnetic. These results suggest d orbital spatial extent as a structural parameter that influences phase transition sequences, and magnetic response under extreme electronic excitation, with implications for the ultrafast optical control of electronic and magnetic properties in perovskite based optoelectronic devices. Landau Devonshire analysis shows that irradiation at 0.3 eVatom transiently deepens the polar potential well in unstrained and strained STO and KTO, with the effect amplified approximately 2 fold in strained STO and 6 fold in strained KTO with respect to the unstrained cases.
