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R. G. Herb Condensed Matter Seminar
Origin of the in-plane resistivity anisotropy of the iron pnictides: scattering rate or plasma frequency?
Date: Thursday, February 11th
Time: 10:00 am - 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Michael Schuett, University of Minnesota
Abstract: In-plane resistivity anisotropy has been the prime tool to probe the electronic nematic state of the iron-based high-temperature superconductors. In these correlated phases, the electronic degrees of freedom spontaneously lower the point-group symmetry of the system from tetragonal to orthorhombic. Thus, the elucidation of the origin of the resistivity anisotropy could provide invaluable information about the microscopic nature of the nematic state of the iron pnictides. In general, an anisotropic resistivity anisotropy can be the result of an anisotropic scattering rate (either elastic or inelastic) and/or an anisotropic plasma frequency. To shed light on this problem, here we investigate the impact of spin fluctuations on the anisotropic ac conductivity of the iron pnictides.

We show that spin fluctuations affect both the scattering rate and the effective plasma frequency. Interestingly, the anisotropy in the effective scattering rate is antagonistic to the anisotropy induced in the effective plasma frequency and can become comparable near the nematic transition temperature. As a result, the ac conductivity may seem to be dominated by an effective plasma frequency anisotropy, although the dc conductivity is actually determined solely by the scattering rate anisotropy. Our results agree qualitatively with recent experiments in detwinned iron pnictides, and reveal an unavoidable entanglement between scattering rate anisotropy and plasma frequency anisotropy caused by spin fluctuations.
Host: Alex Levchenko
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