Electronic band structure of a superconducting nickelate probed by the Seebeck coefficient in the disordered limit

• Main Authors: Grissonnanche, G, Pan, G. A, LaBollita, H, Segedin, D. Ferenc, Song, Q, Paik, H, Brooks, C. M, Beauchesne-Blanchet, E, González, J. L. Santana, Botana, A. S, Mundy, J. A, Ramshaw, B. J
• Format: Journal Article
• Language: English
• Published: 19-10-2022
• Subjects: Physics - Strongly Correlated Electrons; Physics - Superconductivity
• DOI: 10.48550/arxiv.2210.10987

Superconducting nickelates are a new family of strongly correlated electron
materials with a phase diagram closely resembling that of superconducting
cuprates. While analogy with the cuprates is natural, very little is known
about the metallic state of the nickelates, making these comparisons difficult.
We probe the electronic dispersion of thin-film superconducting 5-layer ($n=5$)
and metallic 3-layer ($n=3$) nickelates by measuring the Seebeck coefficient,
$S$. We find a temperature-independent and negative $S/T$ for both $n=5$ and
$n=3$ nickelates. These results are in stark contrast to the strongly
temperature-dependent $S/T$ measured at similar electron filling in the cuprate
La$_{1.36}$Nd$_{0.4}$Sr$_{0.24}$CuO$_4$. The electronic structure calculated
from density functional theory can reproduce the temperature dependence, sign,
and amplitude of $S/T$ in the nickelates using Boltzmann transport theory. This
demonstrates that the electronic structure obtained from first-principles
calculations provides a reliable description of the Fermiology of
superconducting nickelates, and suggests that, despite indications of strong
electronic correlations, there are well-defined quasiparticles in the metallic
state. Finally, we explain the differences in the Seebeck coefficient between
nickelates and cuprates as originating in strong dissimilarities in impurity
concentrations. Our study demonstrates that the high elastic scattering limit
of the Seebeck coefficient reflects only the underlying band structure of a
metal, analogous to the high magnetic field limit of the Hall coefficient. This
opens a new avenue for Seebeck measurements to probe the electronic band
structures of relatively disordered quantum materials.