Differentiated roles of Lifshitz transition on thermodynamics and superconductivity in La<sub>2-</sub><i><sub>x</sub></i>Sr<i><sub>x</sub></i>CuO<sub>4</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 35914123.
- Also identified by DOI 10.1073/pnas.2204630119 and PMC identifier 9371668.
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Abstract
The effect of Lifshitz transition on thermodynamics and superconductivity in hole-doped cuprates has been heavily debated but remains an open question. In particular, an observed peak of electronic specific heat is proposed to originate from fluctuations of a putative quantum critical point <i>p*</i> (e.g., the termination of pseudogap at zero temperature), which is close to but distinguishable from the Lifshitz transition in overdoped La-based cuprates where the Fermi surface transforms from hole-like to electron-like. Here we report an in situ angle-resolved photoemission spectroscopy study of three-dimensional Fermi surfaces in La<sub>2-</sub><i><sub>x</sub></i>Sr<i><sub>x</sub></i>CuO<sub>4</sub> thin films (<i>x</i> = 0.06 to 0.35). With accurate <i>k</i><sub>z</sub> dispersion quantification, the said Lifshitz transition is determined to happen within a finite range around <i>x</i> = 0.21. Normal state electronic specific heat, calculated from spectroscopy-derived band parameters, reveals a doping-dependent profile with a maximum at <i>x</i> = 0.21 that agrees with previous thermodynamic microcalorimetry measurements. The account of the specific heat maximum by underlying band structures excludes the need for additionally dominant contribution from the quantum fluctuations at <i>p*</i>. A <i>d</i>-wave superconducting gap smoothly across the Lifshitz transition demonstrates the insensitivity of superconductivity to the dramatic density of states enhancement.