Abstract
Topology, quantum geometry, and superconductivity in quantum materials have become central themes in modern condensed matter physics. In this thesis, we investigate several systems that exemplify the interplay among these concepts, including non-centrosymmetric achiral materials, Kagome antiferromagnets, and superconductors with finite-momentum pairing and anisotropic superconductors.Specifically, in chapter II, we demonstrate the existence of the topological Fermi-arc-like surface states (FALSSs) in Kramers nodal line metals (KNLMs). Notably, as achiral symmetries are gradually broken, the KNLM transitions into a Kramers Weyl semimetal (KWS), allowing the FALSSs to evolve continuously into the Fermi arc states of the KWS.
In Chapter III, we investigate the Kagome material FeSn and CoSn through first-principles calculations. Based on the results, we further study Berry curvature quadrupole of FeSn and the edge states of monolayer CoSn.
In Chapter IV, we propose a new mechanism for realizing Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) Cooper pairing states within flat bands, Unlike conventional the conventional paradigm such as the Zeeman effect, the mismatches in the quantum geometry of paired electrons drive the flat-band FFLO instability.
In chapter V, we show that a direct current bias injected off principal axes in two-dimensional anisotropic superconductors converts anisotropy into transverse nonreciprocity, enabling supercurrent diode effect (SDE). When the control bias exceeds its critical value, the transverse dissipationless currents can only flow unidirectionally. Our findings open new avenues for developing nonreciprocal superconducting electronic devices.
| Date of Award | 2026 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Supervisor | Kam Tuen LAW (Supervisor) |
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