Universal renormalization group flow toward perfect Fermi-surface nesting driven by enhanced electron-electron correlations in monolayer vanadium diselenide

Abstract

Reducing the thickness of three-dimensional samples on appropriate substrates is a promising way to control electron-electron interactions, responsible for so called electronic reconstruction phenomena. Although the electronic reconstruction has been investigated both extensively and intensively in oxide heterostructure interfaces, this paradigm is not well established in the van der Waals heterointerface system. In the present study, we examine the nature of a charge ordering transition in monolayer vanadium diselenide $({\text{VSe}}_{2})$. This two-dimensional phase transition would be distinguished from that of ${\text{VSe}}_{2}$ bulk samples, driven by more enhanced electron-electron correlations. We recall that ${\text{VSe}}_{2}$ bulk samples show a charge-density-wave (CDW) transition around ${T}_{\text{CDW}}\ensuremath{\sim}105\phantom{\rule{4pt}{0ex}}\text{K}$. This bulk phase transition results from Fermi-surface nesting properties, where the low-temperature CDW state coexists with itinerant electrons of residual Fermi surfaces. Recently, angle-resolved photoemission spectroscopy measurements [Nano Lett. 18, 5432 (2018)] uncovered that the Fermi-surface nesting becomes perfect, where the dynamics of hot electrons is dispersionless along the orthogonal direction of the nesting wave vector. In addition, scanning tunneling microscopy measurements [Nano Lett. 18, 5432 (2018)] confirmed that the resulting CDW state shows essentially the same modulation pattern as the three-dimensional system of ${\text{VSe}}_{2}$. Here, we perform the renormalization group analysis based on an effective-field theory in terms of critical CDW fluctuations and hot electrons of imperfect Fermi-surface nesting. As a result, we reveal that the imperfect nesting universally flows into perfect nesting in two dimensions, where the Fermi velocity along the orthogonal direction of the nesting vector vanishes generically. We argue that this electronic reconstruction is responsible for the observation [Nano Lett. 18, 5432 (2018).] that the CDW transition temperature is much more enhanced to be around ${T}_{\text{CDW}}\ensuremath{\sim}350\phantom{\rule{4pt}{0ex}}\text{K}$ than that of the bulk sample.