Author : Anthony Lyle Edgeton
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (142 download)
Book Synopsis Heteroepitaxy of Quantum Oxides for Emergent Electronic Phenomena by : Anthony Lyle Edgeton
Download or read book Heteroepitaxy of Quantum Oxides for Emergent Electronic Phenomena written by Anthony Lyle Edgeton and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growth of high-quality epitaxial thin films and thin film heterostructures plays a critical role in advancing the field of quantum materials. At reduced dimensions, thin films can offer unique functionalities compared to their bulk counterparts aimed at harnessing quantum mechanical properties. By precisely engineering thin films through novel synthesis routes, principles in defect design, and heterostructuring, the complex interplay between spin, charge, lattice and orbital degrees of freedom is revealed. In this thesis, I present approaches to engineering novel electronic phenomena in three prototypical complex oxide thin film quantum material systems: Sr3SnO, SrTiO3, and BaPb1-xBixO3. Topological materials are derived from the interplay between symmetry and topology. Advances in topological band theories have led to the prediction that the antiperovskite oxide Sr3SnO is a topological crystalline insulator, a new electronic phase of matter where the conductivity in its (001) crystallographic planes is protected by crystallographic point group symmetries. Realization of this material, however, is challenging. Guided by thermodynamic calculations we design and implement a deposition approach to achieve the adsorption-controlled growth of epitaxial Sr3SnO single-crystal films by molecular-beam epitaxy (MBE). In-situ transport and angle-resolved photoemission spectroscopy measurements reveal the metallic and non-trivial topological nature of the as-grown samples. Compared with conventional MBE, the synthesis route used results in superior sample quality and is readily adapted to other topological systems with antiperovskite structures. The successful realization of thin films of topological crystalline insulators opens opportunities to manipulate topological states by tuning symmetries via epitaxial strain and heterostructuring. Point defects play a major role in tuning the properties of materials. In quantum heterostructures based on complex oxides, however, the control of individual point defects continues to be challenging arising mostly from inherent non-stoichiometry. Herein, the ability to tune point defects in oxide-based quantum heterostructure LaAlO3/SrTiO3 (LAO/STO) is demonstrated using a newly-developed metal-organic pulsed laser deposition (MOPLD) technique. Density functional theory (DFT) calculations predict that increasing the ratio of [antisite Ti (TiSr)]/[strontium vacancies (VSr)] reduces the equilibrium amount of oxygen vacancies (VO) which is the most dominant scattering center at low temperatures. X-ray diffraction and Raman spectroscopy show that the MOPLD technique, with titanium tetraisopropoxide (TTIP) used as Ti source, provides a wide process parameter window for controlling the stoichiometry of STO without inducing structural alterations. Depth-resolved cathodoluminescence spectroscopy reveals that STO films grown at larger TTIP flux have a higher ratio of [TiSr]/[VSr], and lower [VO], leading to high mobility of two-dimensional electron gas at the interface of LAO/STO at low temperature and clear Shubnikov de Haas oscillations. These results provide new insights into point defect engineering of the next generation of complex oxide thin films and heterostructures to investigate novel quantum phenomena. The introduction of new mechanisms and materials platforms for efficient spin manipulation is of fundamental and technological interest to realize the full potential of spintronics. Bismuthate superconductors have long been considered as centrosymmetric systems with weak spin-orbit coupling. Remarkably, in bismuthate-based superconductor-ferromagnet heterostructures, we report giant spin-orbit torque (SOT) driven by spin polarization in the normal state of Ba(Pb,Bi)O3 heterostructures. Using spin-torque ferromagnetic resonance (ST-FMR) and d.c. non-linear Hall measurements, we find a robust SOT efficiency exceeding unity and demonstrate current driven magnetization switching at current densities as low as 4©7105 Acm−2. We postulate the emergence of hidden Rashba-like physics due to electric fields from local structural distortions. Our results suggest the importance of hidden forms of spin polarization for engineering efficient spintronics and renew questions of the superconducting pairing in bismuthates.
