Theory of Superconductivity in La3Ni2O7 and La4Ni3O10: Pairing Mechanism and Transition Temperature vs Pressure

王强华

南京大学物理学院

报告时间：2025年4月14日（周一）下午15:30

报告地点：紫金港校区段永平教学楼2号楼212报告厅

摘要：

In this talk, we discuss the pairing mechanism and pairing symmetry in the new superconductors La₃Ni₂O₇ and La₄Ni₃O₁₀. Using functional renormalization group, variational quantum Monte Carlo, as well as renormalized mean field theory for low energy effective model, we find the pairing is triggered by spin fluctuations, which differ slightly from La₃Ni₂O₇ to La₄Ni₃O₁₀, as well as Hund’s coupling. The pairing symmetry is s_(+/-), with sign change of the gap function on the various Fermi pockets. The interlayer coupling and the multi-orbital nature of the sample play key roles in forming the s_(+/-) pairing. Under the hydrostatic pressure up to 80 GPa for La₃Ni₂O₇, we construct the band structure and tight biding models, and by systematic fRG we find the pairing symmetry is consistently s_(+/-), but the transition temperature drops monotonically with pressure, because of the weakening of the spin fluctuations. The results are in qualitative agreement with the experiments, and shed lights on the itinerant vs local moment picture for the electrons in the superconducting La₃NI₂O₇.

报告人简介：

王强华教授，1993年于南京大学获博士学位，之后留校工作。1995-1997年在香港大学做博士后研究工作，2000-2002年在加州伯克利大学访问研究，2002年起任南京大学教授。获2003年度国家杰出青年基金资助，受聘2006-2009年度教育部长江学者特聘教授。 获国家教委科技进步奖1项，江苏省科学技术奖1项。从事凝聚态理论方面的研究，主要研究方向为强关联电子系统中的超导等物质态的物理性质及其微观机理。发表Nature, Phys. Rev. Lett, Phys. Rev. X, Nature Physics, Nature Communications, Phys. Rev. B等论文多篇。提出并命名准粒子散射相干效应；提出和发展处理强关联系统物理的非约束及有限温情况下的重整化平均场方法；提出和发展基于费米子双线性散射模式分解的泛函重整化群方案; 揭示和发现若干强关联体系中的超导微观机理和超导配对特性，以及其它相关磁性和拓扑物质态特性。