Date of Completion

5-4-2018

Embargo Period

5-4-2018

Keywords

Superoxygenated cuprates, superoxgenated nickelates, charge order, nematicity, cobalt telluride, nanoribbons, quantum spin hall effect

Major Advisor

Barrett O. Wells

Associate Advisor

Joseph I. Budnick

Associate Advisor

Nora Berrah

Field of Study

Physics

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Electronic orders in cuprates and nickelates have been of great interest in condensed matter physics. In particular, well-ordered charge and spin stripes have been observed. Charge stripes were observed in most of the 214 cuprates except the superoxygenated ones. Stripe-like spin ordering was found in these superoxygenated cuprates.

Here I present a resonant x-ray scattering study on our superoxygenated cuprates. The evidence for seeing charge order is well established from the data. This is one of the first results that evidently shows charge order appears in a low-temperature orthorhombic structure. Additionally, our charge-ordered sample shows an absence of a scattering that is reported to be related to an electronic nematicity associated with stripe-like charge order. Our discovery implies different ordering pattern of charges than other compounds.

In our superoxygenated nickelates, a nematic-like order parameter is found associated with an incommensurate charge order identified in another similar sample. The transition temperature matches a typical one for charge order.

I will also present three works, one on 113-type cobalt oxide films, one on cobalt telluride compounds and one on strained nanoribbons. The purpose to grow high-quality epitaxial cobalt oxide films with 0.25 doping is to search for charge order. In the cobalt telluride project I show how our result helps to identify the magnetic source of the cobalt-tellurium compound. I will also include a discussion on topological phases in strained squared ribbons. These projects give promising results and opens interesting further research.

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