标题： 分子固体$κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$绝缘相和超导相的起源 显示英文标题

标题： Origin of the insulating and superconducting phases in molecular solid $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$

摘要： 最近对有机分子固体的研究因其复杂的相图和光诱导现象而受到关注，例如莫特绝缘体、自旋液体相和超导性。 然而，在$\kappa$-(BEDT-TTF)$_2$X 系列中，实验观察与第一性原理计算之间存在差异，这阻碍了对其性质的理解。 在此，我们利用最近开发的 DFT+GOU 方法重新研究$\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$的电子结构，以修正分子固体中分子轨道态的能量水平。 我们的工作表明，$\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$的绝缘电子结构来源于BEDT-TTF二聚体的最高占据分子轨道和最低未占据分子轨道状态之间的能隙，这些二聚体是分子固体的周期单元。我们验证了计算结果提供的带隙、光学电导率以及金属-绝缘体转变随压力的变化与实验观测结果一致。 特别是，来自费米能级平带态的超导穹顶$\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$被再现了。 此外，我们构建了一个新的低能晶格模型，基于电子结构数据的能力，可用于研究多体物理问题，如量子自旋液体和双空穴动力学。 我们的研究为理解$\kappa$-(BEDT-TTF)$_2$X 系列以及其他复杂有机分子固体中的复杂相图和各种光致现象提供了更深入的理解。 显示英文摘要

摘要： Recent studies of organic molecular solids are highlighted by their complex phase diagram and light-induced phenomena, such as Mott insulator, spin liquid phase, and superconductivity. However, a discrepancy between experimental observation and first-principle calculation on the $\kappa$-(BEDT-TTF)$_2$X family inhibits understanding their properties. Here, we revisit the electronic structure of $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ with the recently developed DFT+GOU method to correct the energy level of molecular orbital states in the molecular solid. Our work reveals that the insulating electronic structure of $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ originates from the energy gap between the highest occupied and the lowest unoccupied molecular orbital states of the BEDT-TTF dimers, that are the periodic unit of the molecular solid. We verify that our calculation result provides consistent band gap, optical conductivity, and evolution of the metal-insulator transition as a function of pressure with experimental observations. Especially, the superconducting dome of $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$, which originates from the flat band state at the Fermi level, is reproduced. Additionally, we constructed a new low-energy lattice model based on the ability of electronic structure data that can be used to address many-body physics, such as quantum spin liquid and double-holon dynamics. Our provides a deeper understanding of the complex phase diagram and various light-induced phenomena in the $\kappa$-(BEDT-TTF)$_2$X family and the other complex organic molecular solids.