Donghui Lu (SIMES Friday Seminar)

Date(s) - Feb 28 2014
11:00 AM - 12:00 PM

Shasta Room, Bldg. 40, Room 361


Role of orbital degree of freedom in iron-based superconductors – experimental observations by ARPES

 Donghui Lu

 Stanford Synchrotron Radiation Lightsource

 The discovery of iron-based superconductors has opened up a new playground toward the ultimate understanding of high-temperature superconductivity.  While this new family of high temperature superconductors shares many similarities with high-Tc cuprates, there are also important disparities in their physical properties and underlying electronic structures.  One fundamental difference is the multi-band and multi-orbital nature of the electronic states near the Fermi level in iron-based superconductors.  In this talk, I will present two case studies of iron-based superconductors by angle-resolved photoemission spectroscopy (ARPES).  For the first part, I will discuss the observation of symmetry breaking orbital anisotropy in iron pnictides Ba(Fe1-xCox)2As2 and NaFeAs [1,2].  For the second part, I will report more recent results on iron chalcogenides, in which a universal strong orbital-dependent correlation effects has been observed, accompanied by a crossover to an orbital-selective Mott phase upon raising temperature [3].  These two examples suggest that the orbital degree of freedom plays an important role in determining the physical properties and possibly the mechanism of high temperature superconductivity in iron-based superconductors.

[1]      Ming Yi, Donghui Lu, Jiun-Haw Chu, James G. Analytis, Adam P. Sorini, Alexander F. Kemper, Brian Moritz, Sung-Kwan Mo, Rob G. Moore, Makoto Hashimoto, Wei-Sheng Lee, Zahid Hussain, Thomas P. Devereaux, Ian R. Fisher, and Zhi-Xun Shen, PNAS 108, 6878 (2011).

[2]      M. Yi, D. H. Lu, R. G. Moore, K. Kihou, C.-H. Lee, A. Iyo, H. Eisaki, T. Yoshida, A. Fujimori and Z.-X. Shen, New Journal of Physics 14, 073019 (2012).

[3]      M. Yi, D. H. Lu, R. Yu, S. C. Riggs, J.-H. Chu, B. Lv, Z. K. Liu, M. Lu, Y.-T. Cui, M. Hashimoto, S.-K. Mo, Z. Hussain, C. W. Chu, I. R. Fisher, Q. Si, and Z.-X. Shen, Phys. Rev. Lett. 110, 067003 (2013).