Electronic structure evolution across the peierls metal-insulator transition in a correlated ferromagnet

P. A. Bhobe, A. Kumar, M. Taguchi, R. Eguchi, M. Matsunami, Y. Takata, A. K. Nandy, P. Mahadevan, D. D. Sarma, A. Neroni, E. Şaşioğlu, M. Ležaić, M. Oura, Y. Senba, H. Ohashi, K. Ishizaka, M. Okawa, S. Shin, K. Tamasaku, Y. KohmuraM. Yabashi, T. Ishikawa, K. Hasegawa, M. Isobe, Y. Ueda, A. Chainani

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9 引文 斯高帕斯(Scopus)


Transition metal compounds often undergo spin-charge-orbital ordering due to strong electron-electron correlations. In contrast, low-dimensional materials can exhibit a Peierls transition arising from low-energy electron-phonon-coupling-induced structural instabilities. We study the electronic structure of the tunnel framework compound K2Cr8O16, which exhibits a temperature-dependent (T-dependent) paramagnetic-toferromagnetic- metal transition at TC = 180 K and transforms into a ferromagnetic insulator below TMI = 95 K. We observe clear T-dependent dynamic valence (charge) fluctuations from above TC to TMI, which effectively get pinned to an average nominal valence of Cr+3.75 (Cr4+:Cr3+ states in a 3:1 ratio) in the ferromagnetic-insulating phase. High-resolution laser photoemission shows a T-dependent BCS-type energy gap, with 2G(0) ~ 3.5(kBTMI) ~ 35 meV. First-principles band-structure calculations, using the experimentally estimated on-site Coulomb energy of U ~ 4 eV, establish the necessity of strong correlations and finite structural distortions for driving the metal-insulator transition. In spite of the strong correlations, the nonintegral occupancy (2.25 d-electrons/Cr) and the half-metallic ferromagnetism in the t2g up-spin band favor a low-energy Peierls metal-insulator transition.

期刊Physical Review X
出版狀態Published - 2015

All Science Journal Classification (ASJC) codes

  • 物理與天文學 (全部)


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