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arXiv 2006.07030cond-mat.str-el
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二氧化钒分子中$d$轨道的超精细相互作用研究

Occupation switching of $d$ orbitals probed via hyperfine interactions in vanadium dioxide

Yasuhiro Shimizu, Takaaki Jin-no, Fumitatsu Iwase, Masayuki Itoh, Yutaka Ueda

摘要:

利用轨道分辨核磁共振(OR-NMR)技术对二氧化钒VO $_2$单晶的金属-绝缘体相变进行了微观研究。各向异性$^{51}$ V奈特位移和核四极频率的观测使我们能够评估轨道相关的自旋磁化率和$d$轨道职业。这一结果与关联金属相中的简并$t_{2g}$轨道和关联绝缘相中的$d$轨道有序相一致。沿着链指向的主要轨道促进自旋单态形成,触发金属-绝缘体转变。磁和电超精细张量的不对称性表明,低对称性晶体场有利于$d$轨道重整,形成局域分子轨道。结果表明,在具有轨道自由度的Mott跃迁中,存在着电子的合作关联和电子-声子耦合。

英文摘要:

Metal-insulator transition was microscopically investigated by orbital-resolved nuclear magnetic resonance (OR-NMR) spectroscopy in a single crystal of vanadium dioxide VO$_2$. Observations of the anisotropic $^{51}$V Knight shift and the nuclear quadrupole frequency allow us to evaluate orbital-dependent spin susceptibility and $d$ orbital occupations. The result is consistent with the degenerated $t_{2g}$ orbitals in a correlated metallic phase and the $d$ orbital ordering in a nonmagnetic insulating phase. The predominant orbital pointing along the chain facilitates a spin-singlet formation triggering metal-insulator transition. The asymmetry of magnetic and electric hyperfine tensors suggests the $d$ orbital reformation favored by a low-symmetry crystal field, forming a localized molecular orbital. The result highlights the cooperative electron correlation and electron-phonon coupling in Mott transition with orbital degrees of freedom.

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