Anomalous spectral-weight transfers unraveling oxygen screening and electronic correlations in the insulator-metal transition of VO 2
2015; American Physical Society; Volume: 91; Issue: 8 Linguagem: Inglês
10.1103/physrevb.91.081112
ISSN1550-235X
AutoresLi Hsia Yeo, Amar Srivastava, Muhammad Aziz Majidi, Ronny Sutarto, Feizhou He, Sock Mui Poh, Caozheng Diao, Xiaojiang Yu, M. Motapothula, Surajit Saha, Sunil Ojha, D. Kanjilal, Paolo E. Trevisanutto, Mark B. H. Breese, T. Venkatesan, Andrivo Rusydi,
Tópico(s)Advanced Condensed Matter Physics
ResumoVanadium dioxide $({\mathrm{VO}}_{2})$ undergoes an unusual insulator-metal transition (IMT), and after decades of study, the origin of the IMT remains hotly debated. Here, by analyzing spectral-weight transfers (SWTs) of x-ray absorption spectroscopy at the $\mathrm{V}\phantom{\rule{0.28em}{0ex}}{L}_{3,2}$ and O K edges on specially designed ${\mathrm{VO}}_{2}$ films, we observe ${d}_{||}\phantom{\rule{0.28em}{0ex}}({d}_{{x}^{2}\ensuremath{-}{y}^{2}})$ band splitting at the $\mathrm{V}\phantom{\rule{0.28em}{0ex}}{L}_{3,2}$ edges across the IMT, accompanied by anomalous SWTs as high as $\ensuremath{\sim}12\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ at the $\mathrm{O}\phantom{\rule{0.28em}{0ex}}K$ edge, indicating strong electronic correlations. Surprisingly, a few oxygen vacancies induce dramatic SWTs at the $\mathrm{O}\phantom{\rule{0.28em}{0ex}}K$ edge, but the sample remains conducting. Supported by theoretical calculations, we find that in the metallic state, direct $\mathrm{V}(3{d}_{\ensuremath{\parallel}})\text{-V}(3{d}_{\ensuremath{\parallel}})$ and $\text{O}(2p)\text{-V}(3{d}_{\ensuremath{\parallel}})$ hybridized orbital correlations are screened by $\text{O}(2p)\text{-V}(3{d}_{\ensuremath{\pi}})$ hybridized orbitals, while in the insulating state they are strongly correlated due to changes in the oxygen orbital occupancy. Our result shows the importance of screenings and electronic correlations for IMTs in ${\mathrm{VO}}_{2}$.
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