Electronic Structure Evolution across the Peierls Metal-Insulator Transition in a Correlated Ferromagnet
Electronic Structure Evolution across the Peierls Metal-Insulator Transition in a Correlated Ferromagnet
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DOI：
10.1103/physrevx.5.041004
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发表时间：
2015-10
影响因子：
12.5
通讯作者：
P. A. Bhobe;A. Kumar;M. Taguchi;R. Eguchi;M. Matsunami;Y. Takata;A. Nandy;P. Mahadevan;D. Sarma;A. Neroni;E. Şaşıoğlu;M. Ležaić;M. Oura;Y. Senba;H. Ohashi;K. Ishizaka;M. Okawa;Shik Shin;K. Tamasaku;Y. Kohmura;M. Yabashi;T. Ishikawa;K. Hasegawa;M. Isobe;Y. Ueda;A. Chainani
中科院分区：
文献类型：
--
作者：
P. A. Bhobe;A. Kumar;M. Taguchi;R. Eguchi;M. Matsunami;Y. Takata;A. Nandy;P. Mahadevan;D. Sarma;A. Neroni;E. Şaşıoğlu;M. Ležaić;M. Oura;Y. Senba;H. Ohashi;K. Ishizaka;M. Okawa;Shik Shin;K. Tamasaku;Y. Kohmura;M. Yabashi;T. Ishikawa;K. Hasegawa;M. Isobe;Y. Ueda;A. Chainani
由于强的电子-电子关联，过渡金属化合物经常经历自旋-电荷-轨道有序。相比之下，低维材料可以表现出由低能电子-声子耦合引起的结构不稳定性引起的Peierls跃迁。研究了隧道骨架化合物K2 Cr 8 O 16的电子结构，该化合物在T-C = 180 K时表现出随温度变化的顺磁-铁磁-金属转变，在T-MI = 95 K以下转变为铁磁绝缘体.我们观察到明确的T依赖的动态价（电荷）波动，从上述T-C T-MI，有效地得到钉扎到一个平均名义价的Cr+3.75（Cr 4+：Cr 3+状态在3：1的比例）的铁磁绝缘相。高分辨率激光光电子能谱显示了T依赖的BCS型能隙，2G（0）类似于3.5（k（B）T（MI））类似于35 meV。第一性原理能带结构计算，使用实验估计的现场库仑能量U类似于4 eV，建立强相关性和有限的结构扭曲驱动的金属-绝缘体过渡的必要性。尽管有很强的相关性，非积分占有率（2.25 d电子/Cr）和半金属铁磁性的t（2g）上自旋带有利于低能Peierls金属-绝缘体转变。
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 T-C = 180 K and transforms into a ferromagnetic insulator below T-MI = 95 K. We observe clear T-dependent dynamic valence (charge) fluctuations from above T-C to T-MI, 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) similar to 3.5(k(B)T(MI)) similar to 35 meV. First-principles band-structure calculations, using the experimentally estimated on-site Coulomb energy of U similar to 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 t(2g) up-spin band favor a low-energy Peierls metal-insulator transition.