通过氦离子辐照调控SrVO₃薄膜的晶体场与轨道Widom线
Tuning crystal-fields by He-irradiation and orbital Widom line in SrVO$_3$ films
AI总结：
本研究通过DFT+DMFT方法揭示SrVO₃薄膜氦离子辐照引发金属-绝缘体相变的核心机制为晶体场分裂，而非此前认为的莫特局域化，还发现了轨道Widom线，确立了离子注入调控关联材料的可行路径。
AI中文摘要：
外延SrVO₃/SrTiO₃薄膜的氦离子辐照会引发金属-绝缘体相变，此前该相变被归因于动能降低导致的莫特局域化。本研究采用密度泛函理论结合动力学平均场理论，表明驱动机制实为辐照诱导的四方膨胀产生的晶体场分裂，而非相互作用与带宽的比值。所得c轴随温度变化的相图与单带哈伯德模型的相图相似，但其临界点衍生出轨道Widom线，该线源于轨道占据而非电荷占据的反常可压缩性。在有效四分之一填充时，类超交换过程更倾向于轨道长程有序而非磁长程有序。本研究结果半定量复现了实验报道的与注量相关的能隙和相变阈值，确立了离子注入是化学扩展关联材料的一条途径。
英文摘要：
Helium-ion irradiation of epitaxial SrVO$_3$/SrTiO$_3$ films causes a metal-insulator transition, so far attributed to a Mott localization driven by a reduced kinetic energy. Using density-functional theory plus dynamical mean-field theory, we show that the driving mechanism is instead the crystal-field splitting generated by the irradiation-induced tetragonal expansion, not the interaction-to-bandwidth ratio. The resulting $c$-axis vs. temperature phase diagram mirrors that of the one-band Hubbard model, but its critical end-point spawns an orbital Widom line, rooted in an anomalous compressibility of orbital, rather than charge occupation. At an effectively quarter filling, superexchange-like processes favor orbital over magnetic long-range order. Our results semi-quantitatively reproduce the fluence-dependent spectral gaps and transition thresholds reported experimentally, establishing ion implantation as a route to chemically expand correlated materials.
