Journal Article

FZJ-2015-06979

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Electronic Structure Evolution across the Peierls Metal-Insulator Transition in a Correlated Ferromagnet

Bhobe, P.  A. ; Kumar, A. ; Taguchi, M. ; Eguchi, R. ; Matsunami, M. ; Takata, Y. ; Nandy, A. K.FZJ* ; Mahadevan, P. ; Sarma, D.  D. ; Neroni, A.FZJ* ; Şaşıoğlu, E.FZJ* ; Ležaić, M.FZJ* ; Oura, M. ; Senba, Y. ; Ohashi, H. ; Ishizaka, K. ; Okawa, M. ; Shin, S. ; Tamasaku, K. ; Kohmura, Y. ; Yabashi, M. ; Ishikawa, T. ; Hasegawa, K. ; Isobe, M. ; Ueda, Y. ; Chainani, A. (Corresponding author)

2015
APS College Park, Md.

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Please use a persistent id in citations: http://hdl.handle.net/2128/9507  doi:10.1103/PhysRevX.5.041004

Abstract: 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-to-ferromagnetic-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.

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Contributing Institute(s):

1. Quanten-Theorie der Materialien (IAS-1)
2. Quanten-Theorie der Materialien (PGI-1)
3. JARA-FIT (JARA-FIT)

Research Program(s):

1. 142 - Controlling Spin-Based Phenomena (POF3-142) (POF3-142)

Appears in the scientific report 2015

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Database coverage:
; ; ; ; Current Contents - Physical, Chemical and Earth Sciences ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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