On the phase diagram of the superconducting ferromagnet UCoGe and other unconventional superconductors

Superconductivity has inspired many scientists all around the world in the past hundred years. The mechanism which causes superconductivity was investigated in detail. Nevertheless, up to now, there is no unifying theory which can describe all the different types of superconductors. Therefore, it is important to collect empirical knowledge of special cases of superconductivity that have emerged in exotic materials in recent years. This thesis is dedicated to an experimental investigation of two fascinating classes of superconductors. The member of the first class, UCoGe, belongs to the family of heavy-fermion system. In this compound, superconductivity forms unexpectedly within the ferromagnetic phase. This makes it a unique laboratory tool to study the experimental realization of equal-spin paring superconductivity. The second type of studied superconductors is topological superconductors: Sr_xBi₂Se₃ and HoPdBi. These compounds belong to the family of materials which exhibit a non-trivial band inversion. The combination of the topological band structure and superconductivity can potentially be applied in spintronics and quantum computation. The main experimental techniques used in the thesis are electron transport and thermal expansion. An important part of the thesis project was devoted to the design and construction of a dilatometer with very high sensitivity that could be rotated in the magnetic field.