论文标题
D $^3 $旋转轨Mott绝缘子中的多极相互作用和磁激发差距
Multipolar interactions and magnetic excitation gap in d$^3$ spin-orbit Mott insulators
论文作者
论文摘要
在具有半填充$ t_ {2g} $的莫特绝缘子中，hund的规则耦合会诱导旋转3/2轨道 - 轨道 - 单孔基态。预期自旋轨道相互作用不会在质量上影响这种系统中低能的自由度。实际上，重型过渡金属的$ d^3 $立方双钙棍（DP）被认为表现出常规的截线磁性。然而，它们的非弹性中子散射光谱具有巨大的差距不清楚。在这里，我们为立方DP ba $ _2 $ y $ y $ y $ o $ $ _6 $（$ b'= $ os，ru）提供了第一原理低能汉密尔顿人，并表明它们包括大量的多极 - 偶极 - octupolar-dipole-octupolar-互换条款。这些术语打破了Spin-3/2 Hamiltonian的连续对称性。计算出的差距与实验非常吻合。偶极 - 二八叠纤维间交换是由于$ t_ {2g}^3 $歧管的激发态引起的，这些均由旋转轨道相互作用与Spin-3/2基态相结合。
In Mott insulators with a half-filled $t_{2g}$ shell the Hund's rule coupling induces a spin-3/2 orbital-singlet ground state. The spin-orbit interaction is not expected to qualitatively impact low-energy degrees of freedom in such systems. Indeed, $d^3$ cubic double perovskites (DP) of heavy transition metals are believed to exhibit conventional collinear magnetic orders. However, their inelastic neutron scattering spectra feature large gaps of unclear origin. Here we derive first-principles low-energy Hamiltonians for the cubic DP Ba$_2$Y$B'$O$_6$ ($B'=$ Os, Ru) and show that they include significant multipolar - dipole-octupolar - intersite exchange terms. These terms break continuous symmetry of the spin-3/2 Hamiltonian opening an excitation gap. The calculated gap magnitudes are in good agreement with experiment. The dipole-octupolar intersite exchange is induced due to excited states of the $t_{2g}^3$ manifold that are admixed by the spin-orbit interaction into the spin-3/2 ground state.
