Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 12: Poster Session Superconductivity

TT 12.31: Poster

Montag, 11. März 2013, 15:00–19:00, Poster D

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

Iron-based superconductors exhibit rich phase diagrams including tetragonal, orthorhombic/antiferromagnetic (o/afm) and superconducting (sc) states. For the AFe₂As₂ (122) (A = Ba, Sr and Ca) compounds, yet another, nonmagnetic collapsed-tetragonal (cT) phase has been observed at high pressure. It has been shown that for Co-doped Ca 122 single crystals, a postgrowth thermal treatment at an annealing temperature T_a can be used to tune the ground state of the system [1]. Recently we provided evidence that T_a mimics the effect of hydrostatic pressure by demonstrating that for properly heat-treated Ca(Fe_1−xCo_x)₂As₂ the salient ground states can be accessed all in one sample by applying small, truly hydrostatic pressure [2]. We present results of electrical resistance and magnetic susceptibility under pressure for this compound with different combinations of x/T_a. The obtained p-T phase diagrams indicate that preserving fluctuations associated with the o/afm transition to low enough temperatures is vital for sc to form here.
[1] S. Ran et al., Phys. Rev. B 83, 144517 (2011)
E. Gati et al., arXiv:1210.5398 (2012)