ORAL: Nematicity in the superconducting mixed state of strain detwinned underdoped Ba(Fe1-xCox)2As2

J. SCHMIDT; BORTULÉ, M.V.; CANFIELD, P.C.; V. BEKERIS; BERMÚDEZ, M. MARZIALI; E. FRADKIN; LOZANO, G.S.; HICKS, C.W.; G. PASQUINI

Buenos Aires

Conferencia; Statphys 2019; 2019

The electronic phase diagrams of highly correlated systems, particularly of a variety of non-conventional superconductors, have been described in the context of an intertwining of multiple orders [1]. A cutting edge topic has emerged from the observation of strongly anisotropic electronic states in both cuprates and Fe based superconductors. Raman and elasto-resistivity experiments [2] have established that this symmetry breaking is consistent with the existence of a true nematic phase, where the transport anisotropy is coupled to magnetic and structural anisotropies, and the response is strongly influenced by the formation of nematic domains. The nematic susceptibility is generally measured by means of elasto-resistivity experiments, a powerful technique involving a number of non-trivial technical challenges. Recently, a novel piezoelectric-based apparatus to achieve large sample strains at cryogenic temperatures, with compensation of undesirable piezoelectric thermal deformations, has been designed [3]. In a recent collaboration, such device has been installed to perform elasto-resistiviy measurements at low temperatures and orientable magnetic fields, in the Low Temperature Laboratory of FCEyN, UBA and we have recently published unveiling results regarding the interplay between nematicity and superconductivity [4]. In fact, up to now, the coupling between nematicity and superconductivity has been poorly addressed. Here we show evidence of nematic effects in the mixed superconducting phase of slightly underdoped Ba(Fe1-xCox)2As2. Elasto-resistivity measurements were done under a rotating magnetic field and the analysis of the angular dependence of physical quantities identifies the cases in which the sample is a detwinned single domain. Moreover we were able to evaluate the effects of nematicity on the in-plane superconductor stiffness. Our results show that although nematicity contributes in a decisive way in the conduction properties, its contributions to the anisotropy properties of the stiffness of the superconducting order parameter is not as significant in these samples.[1] E. Fradkin et al., Rev. Mod. Phys. 87, 457 (2015).[2] F. Kretzschmar et al., Nature Physics 12, 560 (2016); H-H Khuo et al., Science 352, 960 (2016).[3] C. W. Hicks et al., Rev. Sci. Instr. 85, 065003 (2014). [4] J. Schmidt et al., Phys. Rev. B 99, 064515 (2019).