Ever since the discovery of the charge density wave (CDW) transition in the kagome metal, the nature of its symmetry breaking has been under intense debate. While evidence suggests that the rotational symmetry is already broken at the CDW transition temperature (), an additional electronic nematic instability well belowhas been reported based on the diverging elastoresistivity coefficient in the anisotropic channel (). Verifying the existence of a nematic transition belowis not only critical for establishing the correct description of the CDW order parameter, but also important for understanding low-temperature superconductivity. Here, we report elastoresistivity measurements ofusing three different techniques probing both isotropic and anisotropic symmetry channels. Contrary to previous reports, we find the anisotropic elastoresistivity coefficientis temperature independent, except for a step jump at. The absence of nematic fluctuations is further substantiated by measurements of the elastocaloric effect, which show no enhancement associated with nematic susceptibility. On the other hand, the symmetric elastoresistivity coefficientincreases below, reaching a peak value of 90 at. Our results strongly indicate that the phase transition atis not nematic in nature and the previously reported diverging elastoresistivity is due to the contamination from thechannel.
This content will become publicly available on October 1, 2025
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 five-layer () and metallic three-layer () nickelates by measuring the Seebeck coefficient. We find a temperature-independent and negativefor bothandnickelates. These results are in stark contrast to the strongly temperature-dependentmeasured at similar electron filling in the cuprate. The electronic structure calculated from density-functional theory can reproduce the temperature dependence, sign, and amplitude ofin 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.
- Award ID(s):
- 2045826
- PAR ID:
- 10562402
- Publisher / Repository:
- APS
- Date Published:
- Journal Name:
- Physical Review X
- Volume:
- 14
- ISSN:
- 2160-3308
- Page Range / eLocation ID:
- 041021
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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