When cuprate compounds are sufficiently doped with extra holes, the Mott insulating phase gives way to the puzzling phenomenon of high-temperature superconductivity. Here, we use spectroscopic...Show moreWhen cuprate compounds are sufficiently doped with extra holes, the Mott insulating phase gives way to the puzzling phenomenon of high-temperature superconductivity. Here, we use spectroscopic-imaging scanning tunnelling microscopy (SI-STM) to probe two overdoped cuprate samples belonging to the family of BSCCO. The two samples have slightly different doping levels and critical temperatures TC of 3 K and 12 K. At this doping level, the band structure contains a saddle point close to the Fermi surface. As such, one expects to see a van Hove singularity (vHS) peak in the local density of states at every spatial position, i.e. in every STM dI/dV spectrum. Surprisingly, we find that the vHS peak is absent in part of the measured dI/dV spectra. Hence, to enable further investigation into the partial absence of the vHS peak, we developed a phenomenological model that is capable of fitting all the single dI/dV spectra. Using this model, we are able to spatially map the presence of the van Hove singularity and to correlate its energy to the width of the measured gap.Show less
Bi(2)Sr(2)Cu(1)O(6+x) is a high-temperature superconductor exhibiting strange metal behaviour. A strange metal shows linear resistivity over a long range of temperatures. The strange metal...Show moreBi(2)Sr(2)Cu(1)O(6+x) is a high-temperature superconductor exhibiting strange metal behaviour. A strange metal shows linear resistivity over a long range of temperatures. The strange metal behaviour can possibly be explained by the Anti-de Sitter (AdS)/Conformal Field Theory (CFT) correspondence. In order to investigate the correspondence, a method for reliably measuring the strange metal phase is required. Because measurements on macroscopic crystals deviate from the expected linear resistivity due to C-axis contribution, microscopic Bi(2)Sr(2)Cu(1)O(6+x) flakes had to be used for the measurements. Therefore macroscopic crystals were exfoliated and the resulting flakes were contacted with electron beam lithography. Observing the strange metal regime of Bi(2)Sr(2)Cu(1)O(6+x) under the superconducting dome furthermore requires high current densities and high magnetic fields. These prerequisites for breaking the superconducting phase were obtained by structuring the contacted flakes using a Focused Ion Beam. After successfully contacting the flakes, linear resistivity was actually observed. Calculations on a Hall-bar and a constriction then yielded values for the resistivity of Bi(2)Sr(2)Cu(1)O(6+x) in agreement with literature. By contacting flakes showing the strange metal behaviour the first step for research into the AdS/CFT correspondence has been taken.Show less
