Hund-Heisenberg model in superconducting infinite-layer nickelates
Hund-Heisenberg model in superconducting infinite-layer nickelates
复制标题
超导无限层镍酸盐中的洪德-海森堡模型
DOI：
10.1140/epjb/e2020-10343-7
复制
发表时间：
2020-12-02
影响因子：
1.6
通讯作者：
Ding, Yang
中科院分区：
文献类型：
--
作者：
Chang, Jun;Zhao, Jize;Ding, Yang
基于双波段模型，从理论上研究了新发现的无限层镍酸盐Nd1-xSrxNiO2的非常规超导性。通过输运实验分析，我们提出掺杂空穴主要以带电载流子形式进入Ni d（xy）或/和d（3z2-r2）轨道，并形成导电带。通过现场Hund耦合，将掺杂空穴与d（x2-y2）轨道带的Ni局域空穴耦合。我们证明了这个双波段模型可以进一步简化为亨德-海森堡模型。利用简化模型，我们证明了临界T-c以上的非费米液态可能来自于局域空穴的自旋涨落耦合的载流子。在超导阶段，短程自旋涨落将载流子介导成库珀对，建立了d（x2-y2）波超导性。我们进一步预测，即使在很低的温度下，与局部磁矩耦合的掺杂空穴仍然保持流动，因此在镍酸盐中几乎不会出现赝隙。我们的工作为强相关多轨道系统提供了一种新的超导机制，并为探索过渡态或稀土金属氧化物中的新超导体铺平了一条独特的道路。
We theoretically investigate the unconventional superconductivity in the newly discovered infinite-layer nickelates Nd1-xSrxNiO2 based on a two-band model. By analyzing the transport experiments, we propose that the doped holes dominantly enter the Ni d(xy) or/and d(3z2-r2) orbitals as charged carriers, and form a conducting band. Via the onsite Hund coupling, the doped holes are coupled to the Ni localized holes in the d(x2-y2) orbital band. We demonstrate that this two-band model could be further reduced to a Hund-Heisenberg model. Using the reduced model, we show the non-Fermi liquid state above the critical T-c could stem from the carriers coupled to the spin fluctuations of the localized holes. In the superconducting phase, the short-range spin fluctuations mediate the carriers into Cooper pairs and establish d(x2-y2)-wave superconductivity. We further predict that the doped holes ferromagnetically coupled with the local magnetic moments remain itinerant even at very low temperature, and thus the pseudogap hardly emerges in nickelates. Our work provides a new superconductivity mechanism for strongly correlated multi-orbital systems and paves a distinct way to exploring new superconductors in transition or rare-earth metal oxides.