Unconventional discontinuous transitions in a two-dimensional system with spin and valley degrees of freedom

Many interesting quasi-two-dimensional materials host effectively conserved low-energy spin and valley isospin degrees of freedom. In a number of these systems isospin symmetry is broken by a cascade of transitions into fractional metal states, where some number of isospin species are spontaneously depleted. Here, the authors study itinerant isospin symmetry breaking transitions in multivalley system, showing that for a range of parameters there is naturally such a cascade of strongly first-order transitions coinciding with a large enhancement of the associated isospin susceptibilities.