Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 27: Superconductivity: Fe-based Superconductors - 122

TT 27.1: Topical Talk

Dienstag, 12. März 2013, 09:30–10:00, H18

Hydrostatic-Pressure Tuning of Magnetic, Nonmagnetic and Superconducting States in Annealed Ca(Fe_1−xCo_x)₂As₂ — •Elena Gati¹, Sebastian Köhler¹, Daniel Guterding¹, Bernd Wolf¹, Stephan Knöner¹, Sheng Ran², Sergey L. Bud’ko², Paul C. Canfield², and Michael Lang¹ — ¹Physikalisches Institut, J.W. Goethe-Universität, SPP 1458, D-60438 Frankfurt (Main), Germany — ²Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

Iron-based superconductors manifest rich phase diagrams where antiferromagnetic (afm), tetragonal (t), orthorhombic (o) and superconducting (sc) phases are observed in close proximity. We report on measurements of the magnetic susceptibility and electrical resistance under ⁴He-gas pressure on single crystals of Ca(Fe_1−xCo_x)₂As₂. We demonstrate that for accurately heat-treated crystals with modest Co-concentration the salient ground states associated with iron-arsenide superconductors, i.e., o/afm, sc, and nonmagnetic collapsed-t states can be accessed all in one sample with reasonably small and truly hydrostatic pressure. Systematic investigations of the various phase transitions and ground states through pressure tuning revealed no coexistence of bulk superconductivity with the o/afm phase which we relate to the strongly first-order character of the o/afm transition in the present compound. Our results [1], together with literature results, indicate that preserving fluctuations associated with the o/afm transition to low enough temperatures is essential for superconductivity to form.
[1] E. Gati et al., arXiv:1210.5398 (2012)