Punktkontaktspektroskopie an den Supraleitern MgB2 und Sr2RuO4 (English shop)

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This dissertation investigates the superconducting properties of magnesium diboride (MgB₂) and strontium ruthenate (Sr₂RuO₄) using point-contact spectroscopy. The research focuses on analyzing superconducting energy gaps and the symmetry of the order parameter to gain insights into the underlying pairing mechanisms. Normal-metal–superconductor point contacts are examined at temperatures significantly below their respective superconducting transition temperatures. Differential conductance measurements are interpreted using Andreev reflection and the Blonder-Tinkham-Klapwijk (BTK) theory. In MgB₂, two characteristic superconducting energy gaps of approximately 1.7 meV and 7 meV are identified and interpreted within a two-band superconductivity model. Investigations of Sr₂RuO₄ reveal direction-dependent spectroscopic properties, double-minimum structures, and zero-bias anomalies. These observations are discussed in relation to an unconventional, potentially p-wave superconducting order parameter. Additional analyses address temperature dependence, contact transparency, and possible surface-bound states. The study provides experimental insights into the electronic structure and distinct superconducting behaviors of both materials.