单组分分子导体[Ni(dmdt)$_2$]中依赖于碎片轨道的自旋涨落
Fragment-orbital-dependent spin fluctuations in the single-component molecular conductor [Ni(dmdt)$_2$]
AI总结：
本文通过多轨道Hubbard模型和随机相位近似，研究了单组分分子导体[Ni(dmdt)$_2$]中依赖于碎片轨道的自旋涨落，发现低温下$\textbf{q}$=$\textbf{0}$涨落主导导致$1/T_{1}T$上升，并揭示了碎片轨道对磁性质的关键作用。
摘要：
受近期核磁共振实验的启发，我们利用随机相位近似，在描述该化合物中狄拉克节线电子系统的多轨道Hubbard模型中，计算了单组分分子导体[Ni(dmdt)$_2$]的自旋磁化率、Knight位移和自旋-晶格弛豫率（$1/T_{1}T$）。该Hubbard模型由三个碎片轨道和通过从头算多体微扰理论计算得到的在位排斥相互作用构成。我们发现，在动量$\textbf{q}$=$\textbf{0}$处以及自旋磁化率对角元素取最大值的不相称波数$\textbf{q}$=$\textbf{Q}$处，存在依赖于碎片轨道的自旋涨落。$\textbf{q}$=$\textbf{0}$和$\textbf{Q}$响应分别在低温和高温下占主导，其边界为费米口袋能量尺度。我们表明，$1/T_{1}T$随温度降低而减小，但在低温下由于$\textbf{q}$=$\textbf{0}$自旋涨落而开始增大，而Knight位移则持续单调减小。这些性质源于该狄拉克节线系统特征波函数引起的分子内反铁磁涨落，该系统由$n$带（$n\geq 3$）模型描述。我们表明，碎片轨道在[Ni(dmdt)$_2$]的磁性质中起着重要作用。
英文摘要：
Motivated by recent nuclear magnetic resonance experiments, we calculated the spin susceptibility, Knight shift, and spin-lattice relaxation rate ($1/T_{1}T$) of the single-component molecular conductor [Ni(dmdt)$_2$] using the random phase approximation in a multi-orbital Hubbard model describing the Dirac nodal line electronic system in this compound. This Hubbard model is composed of three fragment orbitals and on-site repulsive interactions obtained using ab initio many-body perturbation theory calculations. We found fragment-orbital-dependent spin fluctuations with the momentum $\textbf{q}$=$\textbf{0}$ and an incommensurate value of the wavenumber $\textbf{q}$=$\textbf{Q}$ at which a diagonal element of the spin susceptibility is maximum. The $\textbf{q}$=$\textbf{0}$ and $\textbf{Q}$ responses become dominant at low and high temperatures, respectively, with the Fermi-pocket energy scale as the boundary. We show that $1/T_{1}T$ decreases with decreasing temperature but starts to increase at low temperature owing to the $\textbf{q}$=$\textbf{0}$ spin fluctuations, while the Knight shift keeps monotonically decreasing. These properties are due to the intra-molecular antiferromagnetic fluctuations caused by the characteristic wave functions of this Dirac nodal line system, which is described by an $n$-band ($n\geq 3$) model. We show that the fragment orbitals play important roles in the magnetic properties of [Ni(dmdt)$_2$].
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
