Zheng Huihuo, Wagner Lucas K
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080, USA.
Phys Rev Lett. 2015 May 1;114(17):176401. doi: 10.1103/PhysRevLett.114.176401. Epub 2015 Apr 27.
Vanadium dioxide (VO2) is a paradigmatic example of a strongly correlated system that undergoes a metal-insulator transition at a structural phase transition. To date, this transition has necessitated significant post hoc adjustments to theory in order to be described properly. Here we report standard state-of-the-art first principles quantum Monte Carlo (QMC) calculations of the structural dependence of the properties of VO2. Using this technique, we simulate the interactions between electrons explicitly, which allows for the metal-insulator transition to naturally emerge, importantly without ad hoc adjustments. The QMC calculations show that the structural transition directly causes the metal-insulator transition and a change in the coupling of vanadium spins. This change in the spin coupling results in a prediction of a momentum-independent magnetic excitation in the insulating state. While two-body correlations are important to set the stage for this transition, they do not change significantly when VO2 becomes an insulator. These results show that it is now possible to account for electron correlations in a quantitatively accurate way that is also specific to materials.
二氧化钒（VO₂）是强关联体系的一个典型例子，它在结构相变时会发生金属-绝缘体转变。迄今为止，为了恰当地描述这种转变，必须对理论进行重大的事后调整。在此，我们报告了关于VO₂性质的结构依赖性的标准的、最先进的第一性原理量子蒙特卡罗（QMC）计算。使用这种技术，我们明确地模拟了电子之间的相互作用，这使得金属-绝缘体转变能够自然出现，重要的是无需特殊调整。QMC计算表明，结构转变直接导致了金属-绝缘体转变以及钒自旋耦合的变化。这种自旋耦合的变化导致了在绝缘态下与动量无关的磁激发的预测。虽然两体关联对于为这种转变奠定基础很重要，但当VO₂变成绝缘体时，它们并没有显著变化。这些结果表明，现在有可能以一种定量准确且针对特定材料的方式来考虑电子关联。
