Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 98: Poster Session: Superconductivity

TT 98.17: Poster

Donnerstag, 15. März 2018, 15:00–19:00, Poster B

Magnetic and electronic excitations in underdoped YBCO — •Ulrike Zweck, Mirko Riedl, Andreas Baum, Daniel Jost, Andreas Erb, and Rudolf Hackl — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany

The interrelation of magnetism, charge order and superconductivity is among the most complex open problems in the cuprates and possibly the key for understanding unconventional superconductivity. YBa₂Cu₃O_{6 + x} is a laboratory for systematic studies since single crystals with extremely high purity can be prepared. In addition, the most interesting doping range 0 ≤ p ≤ 0.18 with p the number of holes per CuO₂ formula unit can be accessed by varying x between 0 and 1. For the intended Raman scattering experiments homogeneously doped and highly ordered crystals are crucial since impurities or residual strain compromise the results. In a first step crystals with oxygen contents of approximately x = 0.56 and x = 0.67 were prepared. For improving the order in the crystals the temperature and the oxygen partial pressure were reduced simultaneously after the initial annealing step at constant temperature in order to keep the oxygen concentration in the crystals constant. In this way the ordering was already substantially improved. After detwinning the crystals were equilibrated following the protocol of Liang et al. [Physica C 336, 57 (2000)]. The resulting transition temperatures were 60 and 66 K. For x = 0.56 the two-magnon excitation in B_1g symmetry was found in the expected energy range as opposed to what was observed earlier in quenched samples.