NOVEL MAGNETOTRANSPORT EFFECTS AT OXIDE INTERFACES: PROBING QUANTUM BEHAVIOR AND TOPOLOGICAL CHARACTERISTICS

Abstract

Topology, as recognized by the 2016 Nobel Prize in Physics, has emerged as a fundamental concept in solid-state physics, offering a new framework to understand electronic and magnetic states that are robust against perturbations. These topological properties, which are preserved under continuous deformations, enable novel functionalities for information storage, processing, and beyond. The realization of topologically non-trivial states is governed by various material parameters, including crystalline symmetry, electron correlations, spin-orbit coupling, and magnetic interactions. As a result, topological materials—characterized by stable surface states and topologically protected electronic features—have become central to both theoretical studies and practical applications in fields like quantum computing, energy-efficient electronics, and magnetic memory. These materials exhibit robust surface states and topologically protected electronic features, making them prime candidates for exploring exotic quasiparticles such as Weyl fermions and for investigating fundamental phenomena. Among the most promising candidates for topological electronics are perovskite oxides. These materials, with their versatile electronic and magnetic properties, such as high-temperature superconductivity and colossal magnetoresistance, offer a rich platform for exploring topological phenomena. Strong electron correlations and cooperative interactions between charge, spin, and orbital degrees of freedom drive these behaviors. Advancements in epitaxial growth and atomic-scale engineering of complex oxide films have enabled the development of functional materials with properties that surpass those of bulk crystals. Additionally, the ability to precisely control interfacial interactions—such as charge transfer, strain, and magnetic coupling—opens new opportunities for exploring emergent phenomena and advancing the next generation of topological devices. In this work, we present the first experimental evidence of the ABJ anomaly and the possible existence of quasi-2D Weyl fermions at the LaVO3/KTaO3 (LVO/KTO) interface, using magneto-transport techniques. Our measurements reveal significant negative magnetoresistance (NMR) and topological planar Hall effect (PHE) when the electric and magnetic fields are applied parallel, indicative of the topological nature of the electronic states at the interface. Additionally, we observe an enhancement in the charge relaxation time, which is attributed to the ABJ anomaly. Temperature-dependent measurements show a clear correlation between NMR and PHE, offering deeper insights into the mechanisms governing the behavior of these topological states. vii Further, we investigate the realization of Dirac-like band dispersion at the LVO/KTO interface. Detailed angular and temperature-dependent magnetoresistance measurements reveal linear magnetoresistance (LMR) at high magnetic fields, both in-plane (B ‖ I) and out-of-plane (B ⊥ I), which is consistent with a quantum model of Dirac-like dispersion. We also observe weak antilocalization (WAL) features in the magnetoresistance at low fields, which further confirm the presence of a quasi-2D electronic system with non-trivial topological properties. These findings provide a new pathway for designing topological materials based on oxide interfaces, with potential applications in magnetic sensors, non-volatile memory devices, and quantum technologies. The thesis also explores the Shubnikov-de Haas (SdH) oscillations at the EuO/KTaO3 (EuO/KTO) interface, offering new insights into the role of spin texture and electronic structure in momentum space. We observe a non-linear relationship between the Landau index and 1/B, suggesting a non-trivial spin texture that is not accounted for in traditional models of SdH oscillations. Moreover, the constant Berry phase of π, indicative of a Dirac cone-like feature in the electronic structure, is observed, further supporting the topologically non-trivial nature of these systems. Additionally, we identify a surprising angular dependence of quantum mobility, which shows a cosine-squared relationship with the relative angle between the applied electric and magnetic fields. This discovery opens up new directions for the study of quantum materials and their application in next-generation quantum devices.