The transition metal dichalcogenides offer significant promise for the tunable realisation and application of correlated electronic phases. However, tuning their properties requires an understanding of the physical mechanisms underlying their experimentally observed ordered phases, and in particular the extent to which lattice vibrations are a necessary ingredient. Here we present a potential mechanism for charge-density-wave formation in monolayers of vanadium diselenide in which the key role at low energies is played by a combination of electron–electron interactions and nesting. There is a competition between superconducting and density-wave fluctuations as sections of the Fermi surface are tuned to perfect nesting. This competition leads to charge-density-wave order when the effective Heisenberg exchange interaction is comparable to the effective Coulomb repulsion. When all effective interactions are purely repulsive, it results instead in d-wave superconductivity. We discuss the possible role of lattice vibrations in enhancing the effective Heisenberg exchange during the earlier stages of the renormalisation group flow.

过渡金属二卤化物为相关电子相的可调实现和应用提供了重要的希望。但是，调整它们的特性需要了解其实验观察到的有序相背后的物理机制，尤其是晶格振动是必要成分的程度。在这里，我们介绍了二硒化钒单层中电荷密度波形成的潜在机理，其中低能的关键作用是通过电子-电子相互作用和嵌套的结合。当费米表面的各个部分被调整为完美的嵌套时，超导和密度波波动之间存在竞争。当有效的海森堡交换相互作用可与有效的库仑排斥相媲美时，这种竞争导致电荷-密度-波序。当所有有效的交互作用都是排斥性的时，它会导致d波超导。我们讨论了在重新归一化群流的早期阶段，晶格振动在增强有效的海森堡交换中的可能作用。