Kekulé Order from Diffuse Nesting near Higher-Order Van Hove Points

Area of Science:

• Condensed matter physics
• Materials science
• Theoretical physics

Background:

• Translation symmetry-breaking order is typically suppressed by the absence of Fermi surface nesting.
• Higher-order Van Hove singularities (HOVHS) often lack the necessary Fermi surface nesting for such orders.

Purpose of the Study:

• To investigate the emergence of symmetry-breaking orders near HOVHS.
• To explore a novel mechanism for Fermi surface instabilities.

Main Methods:

• Unbiased renormalization group calculations.
• Modeling the breathing kagome lattice.

Main Results:

• Anisotropic band-flattening at HOVHS, combined with Fermi surface broadening, leads to approximate nesting.
• This diffuse nesting occurs at a wave vector independent of the Fermi surface's precise shape.
• A sqrt[3]×sqrt[3] Kekulé density wave formation is observed.

Conclusions:

• Diffuse nesting is a new mechanism driving Fermi surface instabilities.
• This mechanism can stabilize symmetry-breaking orders even without traditional Fermi surface nesting.
• The findings challenge existing assumptions about the suppression of such orders near HOVHS.