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<p>In cuprate superconductors, the highest <i>T</i><sub>c</sub> is possessed by the HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+δ</sub> (Hg-1223) system at ambient pressure, but the reason remains elusive. Here we report the scanning tunneling measurements on the Hg-1223 single crystals with <i>T</i><sub>c</sub> ≈ 134 K. The observed gaps determined from the tunneling spectra (STS) can be categorized into two groups: the smaller gap <i>Δ</i><sub>1</sub> ranges from about 45–70 meV, while the larger gap <i>Δ</i><sub>2</sub> from about 65 to 98 meV. The STS was measured up to 200 K and the larger gap can persist well above <i>T</i><sub>c</sub>, indicating a pseudogap feature which may reflect the strong pairing energy in the inner layer. Interestingly, an extremely strong particle-hole asymmetry is observed in associating with a very robust coherence-like peak at the bias of the larger gap in the hole branch of the Bogoliubov dispersion. We argue that the observed asymmetry results may be from the interplay of a flat band (van Hove singularity) in the electronic spectrum and the larger gap in the underdoped (inner) layer. A theoretical approach based on a trilayer model with an interlayer coupling can give a reasonable explanation. Our results provide deep insight into understanding the mechanism of superconductivity in cuprate superconductors.</p>

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Unprecedentedly large gap in HgBa2Ca2Cu3O8+δ with the highest Tc at ambient pressure

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  • 发表日期：

    2025年2月14日

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  • Chuanhao Wen,
  • Zhiyong Hou,
  • Alireza Akbari,
  • Kailun Chen,
  • Wenshan Hong,
  • Huan Yang,
  • Ilya Eremin,
  • Yuan Li,
  • Hai-Hu Wen

摘要

In cuprate superconductors, the highest Tc is possessed by the HgBa2Ca2Cu3O8+δ (Hg-1223) system at ambient pressure, but the reason remains elusive. Here we report the scanning tunneling measurements on the Hg-1223 single crystals with Tc ≈ 134 K. The observed gaps determined from the tunneling spectra (STS) can be categorized into two groups: the smaller gap Δ1 ranges from about 45–70 meV, while the larger gap Δ2 from about 65 to 98 meV. The STS was measured up to 200 K and the larger gap can persist well above Tc, indicating a pseudogap feature which may reflect the strong pairing energy in the inner layer. Interestingly, an extremely strong particle-hole asymmetry is observed in associating with a very robust coherence-like peak at the bias of the larger gap in the hole branch of the Bogoliubov dispersion. We argue that the observed asymmetry results may be from the interplay of a flat band (van Hove singularity) in the electronic spectrum and the larger gap in the underdoped (inner) layer. A theoretical approach based on a trilayer model with an interlayer coupling can give a reasonable explanation. Our results provide deep insight into understanding the mechanism of superconductivity in cuprate superconductors.