标题： 配对对称性和La$_3$Ni$_2$O$_7$薄膜中的超导性 显示英文标题

标题： Pairing symmetry and superconductivity in La$_3$Ni$_2$O$_7$ thin films

摘要： 在常压下，La$_3$Ni$_2$O$_7$和 (La,Pr)$_{3}$Ni$_2$O$_7$薄膜中发现超导性，其转变温度$T_c$超过40 K，这标志着镍酸盐超导体领域的重要进展。 在这里，我们对$\mathrm{La_3Ni_2O_7}$薄膜中的超导性进行了重整化平均场理论研究，使用双层两轨道$t-J$模型。 我们的结果揭示了由$d_{z^2}$轨道的强层间超交换耦合驱动的$s_\pm$波配对对称性，类似于加压的块体情况。 此外，我们大致再现了实验观察到的在$\beta$穴处超导能隙的无节点形状以及超导$T_c$。 此外，通过分析轨道分辨的配对配置及其在费米面上的投影，我们发现$\beta$费米面口袋的无节点特性与$d_{z^2}$和$d_{x^2-y^2}$轨道之间的层间配对有关。 此外，我们确定了$d_{z^2}$和$d_{x^2-y^2}$轨道之间平面内轨道间的$d$波配对的形成，这甚至可以增强主导的层间$s_\pm$波配对。 显示英文摘要

摘要： The recent discovery of superconductivity with a transition temperature $T_c$ over 40 K in La$_3$Ni$_2$O$_7$ and (La,Pr)$_{3}$Ni$_2$O$_7$ thin films at ambient pressure marks an important step in the field of nickelate superconductors. Here, we perform a renormalized mean-field theory study of the superconductivity in $\mathrm{La_3Ni_2O_7}$ thin films, using a bilayer two-orbital $t-J$ model. Our result reveals an $s_\pm$-wave pairing symmetry driven by the strong interlayer superexchange coupling of $d_{z^2}$ orbital, resembling the pressurized bulk case. Also, we roughly reproduce the experimentally observed nodeless shape of the superconducting gap at the $\beta$ pocket and the superconducting $T_c$. In addition, by analysing the orbital-resolved pairing configurations and their projections onto Fermi surface, we find that the nodeless feature of $\beta$ pocket is related to the interlayer pairing within both $d_{z^2}$ and $d_{x^2-y^2}$ orbitals. Moreover, we identify a formation of the inplane inter-orbital $d$-wave pairing between $d_{z^2}$ and $d_{x^2-y^2}$ orbitals, which can even enhance the dominated interlayer $s_\pm$-wave.