Liu, Z.K.Yi, M.Zhang, Y.Hu, J.Yu, R.Zhu, J.-X.He, R.-H.Chen, Y.L.Hashimoto, M.Moore, R.G.Mo, S.-K.Hussain, Z.Si, Q.Mao, Z.Q.Lu, D.H.Shen, Z.-X.2016-06-102016-06-102015Liu, Z.K., Yi, M., Zhang, Y., et al.. "Experimental observation of incoherent-coherent crossover and orbital-dependent band renormalization in iron chalcogenide superconductors." <i>Physical Review B,</i> 92, no. 23 (2015) American Physical Society: 235138. http://dx.doi.org/10.1103/PhysRevB.92.235138.https://hdl.handle.net/1911/90495The level of electronic correlation has been one of the key questions in understanding the nature of superconductivity. Among the iron-based superconductors, the iron chalcogenide family exhibits the strongest electron correlations. To gauge the correlation strength, we performed a systematic angle-resolved photoemission spectroscopy study on the iron chalcogenide series Fe1+ySexTe1−x (0<x<0.59), a model system with the simplest structure. Our measurement reveals an incoherent-to-coherent crossover in the electronic structure as the selenium ratio increases and the system evolves from a weakly localized to a more itinerant state. Furthermore, we found that the effective mass of bands dominated by the dxy orbital character significantly decreases with increasing selenium ratio, as compared to the dxz/dyz orbital-dominated bands. The orbital-dependent change in the correlation level agrees with theoretical calculations on the band structure renormalization, and may help to understand the onset of superconductivity in Fe1+ySexTe1−x.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articlehttp://dx.doi.org/10.1103/PhysRevB.92.235138