Nematic-driven anisotropic electronic properties of underdoped detwinned Ba(Fe1−xCox) 2As2 revealed by optical spectroscopy

International Conference and Exhibition on Mesoscopic & Condensed Matter Physics

June 22-24, 2015 Boston, USA

L Degiorgi

ETH - Z�¼rich, Switzerland

Scientific Tracks Abstracts: J Material Sci Eng

Abstract :

We collect optical reflectivity data as a function of temperature across the structural tetragonal-to-orthorhombic phase transition at TS on Ba(Fe1�xCox)2As2 for x = 0, 2.5% and 4.5%, with uniaxial and in-situ tunable applied pressure in order to detwin the sample and to exert on it an external symmetry breaking field. At T < TS, we discover a remarkable optical anisotropy as a function of the applied pressure at energies far away from the Fermi level and very much reminiscent of a hysteretic-like behavior. Such ananisotropy turns into a reversible linear pressure dependence at T�TS. Moreover, the optical anisotropy gets progressively depleted with increasing Cocontentin the underdoped regime, consistent with the doping dependence of the ortho rhombicity but contrary to the non-monotonic behaviour observed for the dc anisotropy. Our findings bear testimony for an important anisotropy of the electronic structure and thus underscore an electronic polarization upon (pressure) inducing and entering the nematic phase.

Biography :

L Degiorgi was awarded the title of Professor at ETH Zurich in 2005. He is Coordinator (Delegierter), Department of Physics, and he is head of the Optical Spectroscopy Group at the Laboratory for Solid State Physics. Magneto-optical investigation of strongly correlated systems and of novel materials with peculiar ground states is the main topic of his research activity.

Email: degiorgi@solid.phys.ethz.ch