To study the coupling mechanism in high-Tc superconductors we would like to observe them using STM while suppressing the superconductivity with high currents. As the superconductor under study we...Show moreTo study the coupling mechanism in high-Tc superconductors we would like to observe them using STM while suppressing the superconductivity with high currents. As the superconductor under study we choose Bi2S2C1C2O8+x because of easy exfoliatability and doping. Wanting to achieve the required high current densities we decide on lithographically contacting a flake and performing a cleaving in the STM. Several methods are attempted and successful cleaving outside of the STM is achieved. The procedure, however, cannot be reproduced reliably inside the chamber. The journey leading to the result does yield some promising insights to complete the final step.Show less
The advent of high-temperature superconductivity in 1986 [1] shook the foundations of superconductivity. First identified in the cuprate BanLa5−nCu5O5+x, it propelled these elusive materials unto...Show moreThe advent of high-temperature superconductivity in 1986 [1] shook the foundations of superconductivity. First identified in the cuprate BanLa5−nCu5O5+x, it propelled these elusive materials unto the center stage of physics. To let the cuprates divulge their secrets, quasi-particle interference is nowadays an indispensable tool. In the nascent days of the field research using this method primarily has been performed on the underdoped version of the cuprates. The overdoped regime however is less intensively studied. In this study we apply the T-matrix method to model QPI in the overdoped phase. We modify a simulation for underdoped cuprates to make it suitable for application on the desired regime. Then, in order to obtain a quantative analysis of our result we compare experiment and simulation using the Structural Similarity Index Measure. Using this method the filling of the gap, the characteristics of the dispersion bands and the van Hove singularity are investigated.Show less
Copper oxide superconductors (cuprates) are perhaps among the best known strongly correlated materials. Upon chemical (hole) doping of the antiferromagnetic parent compound, a variety of different...Show moreCopper oxide superconductors (cuprates) are perhaps among the best known strongly correlated materials. Upon chemical (hole) doping of the antiferromagnetic parent compound, a variety of different electronic phases emerges, including a mysterious pseudogap phase and unconventional superconductivity. Alternatively, forcing a transport current can also induce phase transitions [1–4]. In this thesis, we outline the first steps towards the local characterization of these current-induced electronic properties using low-temperature Scanning Tunneling Microscopy (STM). After studying the viability of these experiments, we define different regions in the doping-current phase diagram suitable for the local characterization of the various phases. The large current densities and accurate doping control needed to reach these regions require the usage of thin samples that were proven hard to manufacture. However, we present the first steps towards a simple fabrication method that allows cleaving thin exfoliated flakes after being stamped on a Si/SiO2 chip with pre-patterned contacts. After studying and optimizing the cleaving processes of Bi2Sr2CaCu2O8+x flakes onto Gold and Si/SiO2 we conclude that the presented method is not ideal, and suggest more elaborate methods that include conventional lithography approaches.Show less
In recent years Electronic Double Layer (EDL) gating using ionic liquids or organic electrolytes has been successful in tuning carrier densities in materials such as ZnO [1], SrTiO3 [2–4], La2...Show moreIn recent years Electronic Double Layer (EDL) gating using ionic liquids or organic electrolytes has been successful in tuning carrier densities in materials such as ZnO [1], SrTiO3 [2–4], La2-xSrxCuO4 [5] and YBa2Cu3O7- [6]. The potential for studying High-Tc superconductors and Metal-Insulator transition with great flexibility has been shown. The carriers are pulled into a 1nm layer by the accumulation of ions on the surface (EDL). Here the formation the EDL in time is studied on atomically flat SrTiO3 (100) single crystals and electron doped High-Tc superconductor Nd2-xCexCuO4 thin films. At temperatures close to the melting point of the ionic liquid (DEMETFSI) the ability to separate the EDL formation on the contacts from the formation on STO is demonstrated by measuring resistance and gate current as a function of time. This despite the presence of a significant Faradaic current most likely due to oxidation/reduction at the gold surface. It is argued that the EDL formation on the STO originates from the contacts and its growth largely depends on the mobility of the ions. Measurements on (undoped) Nd2CuO4 show a resistance decrease up to 90% at Vg = 3V and thereby showing the potential of EDL gating on electron doped cuprates.Show less
