Detection of electron matter in Fe-pnictides, Fe-chalchogenides, and heavy fermions
Electronic nematicity occurs when the electronic fluid exhibits a lower symmetry than the underlying lattice; exhibiting non-Fermi liquid (NFL)-like behavior. It can be detected a variety of ways and we have found that point contact spectroscopy (PCS) is surprising sensitive to the resulting density of states (DoS) arising from a NFL. In the Fe pnictides and chalcogenides the electronic nematicity is seen as an excess conductance around zero bias appearing at the onset of the fluctuating nematic phase above the structural phase transition (TSPT) and surviving into the electronic nematic state, below TSPT. This can be explained by an increased density of states at the Fermi level arising from orbital fluctuations above TSPT and as an over-damped collective mode below TSPT. We will also show how PCS detects hybridization in heavy fermions, such as URu2Si2 and YbAl3, and in the later, our measurements suggest a new way to define the coherence temperature. We present a new quantum mechanical theory that shows how PCS can be used as a filter for correlated electron states; thereby aiding in our search for new superconductors.
Cm-Bio 3-19 Greene