Pressure Effect and Specific Heat of RBa2Cu3Ox at Distinct Charge Carrier Concentrations: Possible Influence of Stripes

In YBa2Cu3Ox, distinct features are found in the pressure dependence of the transition temperature, dTc/dp, and in DeltaCp*Tc, where DeltaCp is the jump in the specific heat at Tc: dTc/dp becomes zero when DeltaCp*Tc is maximal, whereas dTc/dp has a peak at lower oxygen contents where DeltaCp*Tc vanishes. Substituting Nd for Y and doping with Ca leads to a shift of these specific oxygen contents, since oxygen order and hole doping by Ca influences the hole content nh in the CuO2 planes. Calculating nh from the parabolic Tc(nh) behavior, the features coalesce for all samples at nh=0.11 and nh=0.175, irrespective of substitution and doping. Hence, this behavior seems to reflect an intrinsic property of the CuO2 planes. Analyzing our results we obtain different mechanisms in three doping regions: Tc changes in the optimally doped and overdoped region are mainly caused by charge transfer. In the slightly underdoped region an increasing contribution to dTc/dp is obtained when well ordered CuO chain fragments serve as pinning centers for stripes. This behavior is supported by our results on Zn doped NdBa2Cu3Ox and is responsible for the well known dTc/dp peak observed in YBa2Cu3Ox at x=6.7. Going to a hole content below nh=0.11 our results point to a crossover from an underdoped superconductor to a doped antiferromagnet, changing completely the physics of these materials.Comment: 6 pages, 5 figures Proccedings of the 'Stripes 2000' Conference, Rome (2000

Status of the emittance transfer experiment emtex

In order to improve the injection efficiency of the round UNILAC heavy ion beam into the asymmetric acceptance of the SIS18 it would be of great advantage to decreasethe horizontal emittance by a so called emittance transferto the vertical plane. In this contribution the present statusof the emittance transfer experiment EMTEX at GSI will be reported. A short introduction about the theoretical background of the technique will be given, while the mainpart is dedicated to the practical solutions setting up a testbeam line at GSI. Finally, the results of a first commissioning beam time will be presented. The scheduled beam time to apply the emittance transfer technique foreseen in spring 2014 had to be shifted to calendar week 26 in 2014, just after this conference as some components have not been delivered in time by the contractor. The results and comparison to the theoretical predictions you may find in later publications