Thermopower across the phase diagram of the cuprate La1.6−xNd0.4SrxCuO4: Signatures of the pseudogap and charge density wave phases

Cuprate high-temperature superconductors universally exhibit a phase of charge order and a mysterious pseudogap phase. Using thermopower measurements, the authors explore here how the cuprate La${}_{1.6\ensuremath{-}x}$Nd${}_{0.4}$Sr${}_{x}$CuO${}_{4}$ (Nd-LSCO) evolves across these phases. They find that the thermopower displays a large increase below the pseudogap critical doping point ${p}^{*}$ and becomes negative in the charge order phase below that critical doping point ${p}_{\text{CDW}}$. This evolution hints at profound changes in the electronic structure at ${p}^{*}$ and ${p}_{\text{CDW}}$. They observe that these two critical dopings are well separated, implying that the two phases are clearly distinct.