Date of Award

6-2021

Degree Name

Doctor of Philosophy

Department

Physics

First Advisor

Dr. Clement Burns

Second Advisor

Dr. Pnina Ari-Gur

Third Advisor

Dr. Asghar Kayani

Fourth Advisor

Dr. Lisa Paulius

Keywords

Heavy fermion, Kondo effect, superconductivity, skutterudite, zero-gap semiconductor, specific heat

Abstract

The skutterudite family of materials has garnered a lot of attention in the condensed matter community and it persists to be an important system for exploring the fundamental physics of solids. The initial interest into compounds with this common structure was due to their promising thermoelectric properties giving the possibility of efficient energy harvesting. Since, there has been a huge effort to systematically synthesize new filled skutterudite compounds, as nearly every type of strongly correlated behavior has been found within this family. As the field of topological materials has gained momentum, these materials have also been given a renewed interest in this regard. The skutterudite IrSb3 has been characterized in past studies with a focus on its (high temperature) thermoelectric properties, however not much work has been reported on the low temperature properties of single crystal samples. There have also been conflicting results found in ab initio calculations that have been carried out in the past few decades.

In this study, I report novel properties of single crystal IrSb3 grown using a horizontal flux transport method, those that are in contrast to previous measurements and theoretical calculations. I also discuss the implications of filling IrSb3 with a rare-earth ion and the characterization of the new single crystal skutterudite, Pr0.5Ir4Sb10.2Sn1.8. The structure and composition of these materials are first confirmed through powder x-ray diffraction and energy dispersive x-ray spectroscopy. The physical characterization is carried out through low temperature measurements of the specific heat, resistivity, and magnetization. These measurements show that IrSb3 can express behavior consistent with a zero-gap point fermi surface semimetal, as some calculations predict. This material also shows many transport characteristics common to topological semimetals, such as ultrahigh mobility, extremely large magnetoresistance, and sublinear magnetoresistance. The Pr filled skutterudite shows heavy fermion correlations in the resistivity and specific heat, while the magnetic susceptibility predicts a Kondo temperature Tk ˜4 K . There is also evidence of a superconducting transition seen as a small drop in the resistivity and a diamagnetic signal in the magnetization. Only a very small fraction of material becomes superconducting at low temperatures, possibly due to an impurity phase, superconductivity of reduced dimensionality, or sample inhomogeneity.

Access Setting

Dissertation-Open Access

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