Superconductivity and Ordered Phases in BaNi_2As_2 and UTe_2

Abstract: Topological superconductivity, charge order and electronic nematic phases are all fascinating phases of matter that have been observed in several quantum materials of recent interest. The nematic phase, wherein electronic degrees of freedom drive a reduction in crystal rotational symmetry, is a common motif across a number of high temperature superconductors, while charge order has become a ubiquitous component of several newly studied superconductors. I will discuss the evolution of physical properties, including elastoresistance, in the (Ba,Sr)Ni₂As₂ substitution series, a new electronic nematic system without magnetism or unconventional pairing. Our observation of charge density wave order in the nematic phase of this series evokes comparisons to nematicity in cuprate superconductors, and a strong enhancement of the superconducting transition temperature appears to be driven by nematic fluctuations, establishing a promising route to higher superconducting critical temperatures. I will also overview our recent work on UTe₂, a spin-triplet superconductor with a fascinating landscape of superconducting and magnetic phases and indications of non-trivial topological pairing states. I will review basic properties and our detailed investigations of the gap structure and anomalous normal state properties that have been recently observed.