Nature of the van Hove singularity symmetry-breaking state

Determine the exact nature of the non-superconducting symmetry-breaking ground state that forms at the van Hove singularity near filling factor ν ≈ 0.78 in twisted bilayer WSe₂ with twist angle θ ≈ 3.5°.

Background

In the θ ≈ 3.5° twisted bilayer WSe₂ device, the van Hove singularity occurs near filling factor ν ≈ 0.78. At temperatures below approximately 150 mK, the resistivity develops a dip associated with a symmetry-breaking phase transition. The state is not superconducting, because its resistivity remains nonzero at low temperatures and its magnetoresistance differs from superconducting behavior.

The measurements establish the existence of a symmetry-breaking ground state near the van Hove singularity but do not identify its microscopic order or character. Resolving its exact nature is important for understanding the relationship between the van Hove singularity, strong electronic interactions, and the neighboring superconducting domes.