Seminar H.-J. Grafe

 On Tuesday July 26^th begining at 14:15 dr. sc. Hans-Joachim Grafe from Leibniz Institute for Solid State Research, Dresden (Germany) will within the framework of the SOLeNeMaR project hold a seminar entitled: "New NMR results in the prototypical high temperature superconductors La_2-x Sr_x CuO₄ and YBa₂ Cu₃ O_y " .

 The seminar will be held on the Physics Department, lecture room 201 (I.st floor), and the abstract can be found below:

 "Even after 25 years of intense research on the high temperature superconducting cuprates it is still possible to either prove findings which were not generally accepted, or even to find totally new results which were not known before. In my talk, I will present new NMR results on the prototypical HTSC compounds La_2-x Sr_x CuO₄ and YBa₂ Cu₃ O_y . In the first compound, we could recently prove that the average low temperature orthorhombic structure as determined by x-ray scattering is fully compatible with its local structure determined by a local probe as NMR [1]. In the second compound, we explored the highly underdoped regime (y=6.35-6.6), and found a new NMR signal which proves the emergence of a static order below a critical hole doping of p_c ~ 0.095 [2]. Surprisingly, the pseudogap as determined by the NMR spin lattice relaxation appears only above this critical doping level. Our data suggests that a possibly stripe-like static order competes with the spin-pseudogap phase, whereby both are separated by a critical hole doping p_c .

[1] S.-H. Baek, A. Erb, B. Büchner, and H.-J. Grafe, Phys. Rev. B 85, 184508 (2012)

[2] S.-H. Baek, T. Loew, V. Hinkov, C. T. Lin, B. Keimer, B. Büchner, and H.-J. Grafe, to be published"