Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.
Department of Physics and Astronomy, Seoul National University (SNU), Seoul 08826, Republic of Korea.
Phys Rev Lett. 2015 Dec 31;115(26):266402. doi: 10.1103/PhysRevLett.115.266402. Epub 2015 Dec 28.
We investigated the metal-insulator transition (MIT) driven by all-in-all-out (AIAO) antiferromagnetic ordering in the 5d pyrochlore Cd(2)Os(2)O(7) using optical spectroscopy and first-principles calculations. We showed that the temperature evolution in the band-gap edge and free carrier density were consistent with rigid upward (downward) shifts of electron (hole) bands, similar to the case of Lifshitz transitions. The delicate relationship between the band gap and free carrier density provides experimental evidence for the presence of an AIAO metallic phase, a natural consequence of such MITs. The associated spectral weight change at high energy and first-principles calculations further support the origin of the MIT from the band shift near the Fermi level. Our data consistently support that the MIT induced by AIAO ordering in Cd(2)Os(2)O(7) is not close to a Slater type but instead to a Lifshitz type.
我们通过光学光谱和第一性原理计算研究了全反全出（AIAO）反铁磁序驱动的 5d 钙钛矿 Cd(2)Os(2)O(7)中的金属-绝缘体转变（MIT）。我们表明，带隙边缘和自由载流子密度的温度演化与电子（空穴）能带的刚性上移（下移）一致，类似于 Lifshitz 转变的情况。带隙和自由载流子密度之间的微妙关系为 AIAO 金属相的存在提供了实验证据，这是这种 MIT 的自然结果。在高能下的相关光谱权重变化和第一性原理计算进一步支持了费米面附近能带位移导致的 MIT 起源。我们的数据一致表明，AIAO 有序诱导的 Cd(2)Os(2)O(7)中的 MIT 不是接近 Slater 型，而是 Lifshitz 型。
