The low energy electronic structure of Sr2IrO4 has been well studied and understood in terms of an effective Jeff= 1/2 Mott insulator model. However, little work has been done in studying its high energy electronic behaviors. Here we report a new observation of the anomalous high energy electronic structure in Sr2IrO4. By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4 over a wide energy range, we have revealed for the first time that the high energy electronic structures show unusual nearly-vertical bands that extend over a large energy range. Such anomalous high energy behaviors resemble the high energy waterfall features observed in the cuprate superconductors. While strong electron correlation plays an important role in producing high energy waterfall features in the cuprate superconductors, the revelation of the high energy anomalies in Sr2IrO4, which exhibits strong spin-orbit coupling and a moderate electron correlation, points to an unknown and novel route in generating exotic electronic excitations.

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Published in Scientific Reports, v. 5, article 13036, p. 1-8.

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XJZ thanks financial support from the NSFC (91021006 and 11334010), the MOST of China (973 program No: 2011CB921703, 2011CBA00110, 2012CB821402, 2013CB921700 and 2013CB921904), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020300).

srep13036-s1.pdf (1409 kB)
Supplementary Information

srep13036-f1.jpg (234 kB)
Figure 1: Measured constant energy contours of Sr<sub>2</sub>IrO<sub>4</sub> and its comparison with calculations.

srep13036-f2.jpg (496 kB)
Figure 2: Typical band structures of Sr<sub>2</sub>IrO<sub>4</sub> along high-symmetry cuts in a large energy range.

srep13036-f3.jpg (626 kB)
Figure 3: Momentum dependence of the band structures around Γ and X regions.

srep13036-f4.jpg (356 kB)
Figure 4: Calculated and measured overall band structure of Sr<sub>2</sub>IrO<sub>4</sub>.