Doctor of Philosophy (PhD)


Physics and Astronomy

Document Type



Intermetallic compounds exhibit various interesting phenomena, such us superconductivity and non - trivial topology, which are usually dictated by the interplay of crystal symmetry, spin - orbit coupling, electron – electron and electron – phonon interactions. This dissertation presents the experimental study of interesting phenomena observed in Pd - P – based, and Eu - based compounds due to the interplay between various degrees of freedom.

For Pd-P-based compounds, we find that CaPd2P2 and SrPd2P2 crystallize in a tetragonal space group I4/mmm and exhibit superconductivity below Tc = 1.0 K and 0.7 K, respectively. The antibonding interaction between Pd and P orbitals play a critical role in inducing superconductivity. On the other hand, CaPd1-xP1+x and SrPd1-xP1+x form a honeycomb lattice: one is centrosymmetric and another non-centrosymmetric, respectively. Our study indicates that it is necessary to mix Pd and P site within honeycomb lattice to stabilize the crystal structure. Both compounds are diamagnetic materials and exhibit metallic behavior.

For Eu-based compounds, involving f – electrons, magnetism will play an important role. We discovered a new magnetic semiconductor Eu3Sn2P4, which shows an antiferromagnetic transition at TN = 14 K, and semiconducting behavior with the energy gap of 0.14 eV. Eu can also bring the magnetism into the topologically non-trivial materials, which motivated us to study EuZn2As2, an analogue to EuCd2As2. EuZn2As2 exhibits an A - type antiferromagnetic ordering below TN = 19 K, with strong ferromagnetic fluctuations up to Tfl ~ 200 K. Since the TN and Tfl are two times higher than that for EuCd2As2, it provides a better platform for exploring topological properties in both the magnetically ordered and fluctuation regimes. The high magnetic field resistivity data show giant magnetoresistance (MR) unsaturated up to 60 T and Shubnikov-de Haas quantum oscillations with a single frequency of F = 38 T. Quantitative data analysis indicates that the corresponding hole band has a non - trivial Berry phase and reaches the first Landau level at ~50 T, thus exhibiting linear MR in the quantum limit.



Committee Chair

Jin, Rongying



Available for download on Sunday, March 31, 2030