Experimental approaches to nickelate superconductivity

Abstract: 

Since the discovery of high temperature superconductivity in the copper oxides, there have been sustained experimental and theoretical efforts to understand these phases and discover new materials that could host unconventional superconductivity.  The rare-earth nickelates have been long sought-after as a cuprate analogue, as nickel is adjacent to copper on the periodic table.  In recent years, nickelates have indeed emerged as a major family of unconventional superconductors, with two phenomenologically distinct classes: square-planar nickelates, which can be closely mapped onto hole-doped cuprates, and Ruddlesden-Popper nickelates, which superconduct at high Tcs under applied pressure or strain.  In this talk, I will survey the evolving experimental landscape in this rapidly developing field.  I will focus on our discovery of superconductivity in the layered square-planar nickelates Ndn+1NinO2n+2.  By adjusting the dimensionality n, we tune the nominal nickel count by +1/n holes per Ni1+, enabling us to reveal a full superconducting dome and correlated phases that point to underlying universalities in the phase diagram of square-planar nickelates.  I will also discuss emerging experimental efforts to understand and tune the broader family of correlated nickelate materials.