Twist-decoupled van der Waals layers as a probe for correlated quantum phases

Determining the symmetry breaking order of correlated quantum phases is essential for understanding the microscopic interactions in their host systems. In this talk, I will discuss a new technique based on twist-decoupled van der Waals layers that enables measurements of their electronic band structure and, by studying the backscattering between counter-propagating edge states in transport, determination of the relative spin polarization of their edge modes. We apply this method to twist-decoupled magic-angle twisted bilayer graphene (MATBG) and monolayer graphene, where we find that the broken-symmetry quantum Hall states that extend from the charge neutrality point in MATBG are spin-unpolarized at even integer filling factors. The measurements also indicate that the correlated Chern insulator emerging from half filling of the flat valence band is spin-unpolarized, but suggest that its conduction band counterpart may be spin-polarized. Our results constrain models of spin-valley ordering in MATBG and establish a versatile approach to study the electronic properties of van der Waals systems.