Unified mechanism of charge-density-wave and high-T_c superconductivity protected from oxygen vacancies in bilayer nickelates

摘要

Unconventional charge and spin density-wave states are commonly observed in bilayer nickelates, drawing considerable attention due to their proximity to high-T_c superconductivity in various phase diagrams. However, the nature and mechanisms of charge and spin density-waves (DWs) in nickelates remain poorly understood. Numerous experiments have reported that the charge-density-wave (CDW) transition temperature T cdw and the spin-density-wave (SDW) transition temperature Tsdw are closely related but distinct. However, in contrast to these experiments, previous mean-field-type analyses have yielded only a simple SDW phase. To resolve this key problem, this paper demonstrates that sizable CDW instabilities emerge in proportion to the SDW instability in La₃Ni₂O₇.This behavior is driven by the paramagnon-interference (PMI) mechanism, which captures important electron correlations beyond mean-field theory. Therefore, (i) experimental CDW + SDW coexisting state is naturally explained. In addition, (ii) the CDW + SDW fluctuations cooperatively drive high-T_c superconductivity. Notably, the predicted s-wave SC state is robust against the inner apical O vacancies. Furthermore, (iii) the CDW instability is highly sensitive to the size of the dz2-orbital hole pocket, allowing for the realization of CDW quantum criticality through carrier-doping and pressure application. We find that the coexistence of charge and spin fluctuations is essential in bilayer nickelates, with both playing a cooperative role in mediating high-T_c superconductivity.

材料

• La₃Ni₂O₇

方法

• paramagnon-interference mechanism
• mean-field theory

关键词

• charge density wave
• spin density wave
• cdw quantum criticality
• s wave superconductivity

亮点

• CDW instabilities emerge in proportion to SDW instability via paramagnon-interference mechanism.
• The CDW+SDW fluctuations cooperatively drive high-T_c superconductivity.
• The mechanism is protected from oxygen vacancies.

结论

• Experimental CDW + SDW coexisting state is naturally explained.
• CDW + SDW fluctuations cooperatively drive high-T_c superconductivity.
• The predicted s-wave SC state is robust against the inner apical O vacancies.
• CDW instability is highly sensitive to the size of the d_z2-orbital hole pocket.

主要论断

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研究流程

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