钛铁矿异质结构中基塔耶夫自旋液体边缘的自旋-轨道耦合绝缘体与金属
Spin-Orbit Coupled Insulators and Metals on the Verge of Kitaev Spin Liquids in Ilmenite Heterostructures
AI总结：
本文理论研究了MgIrO3基钛铁矿异质结构，发现其可调控自旋-轨道耦合电子与磁性质，为实现基塔耶夫自旋液体提供平台，并可能支持马约拉纳费米面与拓扑超导。
摘要：
电子关联与相对论性自旋-轨道耦合之间的竞争与合作在固体中产生了多种奇异的量子现象。一个典型的例子是自旋-轨道纠缠的量子液体，它们展现出拓扑序和分数激发等显著特征。基塔耶夫蜂窝模型实现了这类有趣的状态，称为基塔耶夫自旋液体，但其实验可行性仍具挑战性。在此，我们从理论上研究了包含基塔耶夫磁体候选材料MgIrO$_3$的六方异质结构，以主动调控电子和磁性质，从而向实现基塔耶夫自旋液体迈进。对于三种不同结构类型的钛铁矿双层MgIrO$_3$/$A$TiO$_3$（其中$A$ = Mn、Fe、Co和Ni），我们获得了优化的晶格结构、电子能带结构、稳定的磁有序以及有效的磁耦合。我们发现，在所有异质结构中，MgIrO$_3$层均保留了以赝自旋$j_{\ m eff}=1/2$为特征的自旋-轨道耦合能带，但磁态和带隙取决于异质结构的类型以及$A$原子。特别地，一种类型无论$A$为何均为金属性，而另外两种类型大多为绝缘性。我们表明，绝缘情形提供了具有主导基塔耶夫型相互作用的自旋-轨道耦合莫特绝缘态，并伴随因异质结构类型和$A$不同而异的次主导相互作用的组合，而金属情形则实现了具有不同掺杂率的自旋-轨道耦合金属。我们的结果表明，这些六方异质结构是工程化自旋-轨道耦合关联材料的电子和磁性质的良好平台，包括马约拉纳费米面和拓扑超导的可能性。
英文摘要：
Competition and cooperation between electron correlation and relativistic spin-orbit coupling give rise to diverse exotic quantum phenomena in solids. An illustrative example is spin-orbit entangled quantum liquids, which exhibit remarkable features such as topological orders and fractional excitations. The Kitaev honeycomb model realizes such interesting states, called the Kitaev spin liquids, but its experimental feasibility is still challenging. Here we theoretically investigate hexagonal heterostructures including a candidate for the Kitaev magnets, MgIrO$_3$, to actively manipulate the electronic and magnetic properties toward realizing the Kitaev spin liquids. For three different structure types of ilmenite bilayers MgIrO$_3$/$A$TiO$_3$ with $A$ = Mn, Fe, Co, and Ni, we obtain the optimized lattice structures, the electronic band structures, the stable magnetic orders, and the effective magnetic couplings. We find that the spin-orbital coupled bands characterized by the pseudospin $j_{\rm eff}=$ 1/2 are retained in the MgIrO$_3$ layer for all the heterostructures, but the magnetic state and the band gap depend on the types of heterostructures as well as the $A$ atoms. In particular, one type becomes metallic irrespective of $A$, while the other two are mostly insulating. We show that the insulating cases provide spin-orbit coupled Mott insulating states with dominant Kitaev-type interactions, accompanied by different combinations of subdominant interactions depending on the heterostructural type and $A$, while the metallic cases realize spin-orbit coupled metals with various doping rates. Our results indicate that these hexagonal heterostructures are a good platform for engineering electronic and magnetic properties of the spin-orbital coupled correlated materials, including the possibility of Majorana Fermi surfaces and topological superconductivity.
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