We have applied the diffusion quantum Monte Carlo (DMC) method to study the electron confinement and magnetic structure in the (LaTiO3)1/(SrTiO3)5 heterostructure. The DMC results were compared with various density functional theory (DFT) methods, including local density approximation (LDA), generalized gradient approximation (GGA), LDA+U, and GGA+U, as well as the recently proposed strongly constrained appropriately normed (SCAN) and van der Waals-Bayesian error estimation functional (vdW-BEEF). We found that many-body correlations are crucial to accurately describe the localization of the two-dimensional (2D) electron gas around the lanthanum planes. DMC predicts 20% more electron density within the first interfacial titanium layer in (LaTiO3)1/(SrTiO3)5 than LDA+U, suggesting that the degree of confinement of the 2D electron gas in the interfacial region is underestimated with semilocal DFT approximations. DMC yields the ferromagnetic (FM) state as the ground state of (LaTiO3)1/(SrTiO3)5 and the antiferromagnetic (AFM) and nonmagnetic (NM) states that are higher in energy by 37(15) and 238(15) meV per lanthanum atom at the interface, respectively. Most DFT methods yield the FM and NM states within less than 25 meV in energy and could not find the AFM state.

中文翻译：

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（LaTiO3）1 /（SrTiO3）5异质结构的电子约束和磁性：扩散量子蒙特卡洛研究。

我们已经应用了扩散量子蒙特卡罗（DMC）方法来研究（LaTiO3）1 /（SrTiO3）5异质结构中的电子约束和磁性结构。将DMC结果与各种密度泛函理论（DFT）方法进行了比较，包括局部密度逼近（LDA），广义梯度逼近（GGA），LDA + U和GGA + U，以及最近提出的强约束适当归一化（扫描（SCAN）和范德瓦尔斯-贝叶斯误差估计功能（vdW-BEEF）。我们发现，多体关联对于准确描述镧平面周围的二维（2D）电子气的定位至关重要。DMC预测（LaTiO3）1 /（SrTiO3）5的第一界面钛层中的电子密度比LDA + U高20％，这表明用半局部DFT近似低估了界面区域中二维电子气的约束程度。DMC产生铁磁性（FM）态作为（LaTiO3）1 /（SrTiO3）5的基态，反铁磁性（AFM）和非磁性（NM）态的能量高37（15）和238（15）meV界面上的每个镧原子。大多数DFT方法产生的能量小于25 meV的FM和NM状态，无法找到AFM状态。