It has been corroborated in the past that Pauli blockade mechanisms of weakly spin-coupled charge carrier pairs undergoing transitions into doubly occupied singlet states are among the most dominant spin-selection rules influencing room-temperature magnetoresistance and luminescence of organic semiconductors. Thus, at distances long compared to the strip width, they demonstrate that the system is described by a Dirac fermion coupled to an emergent gauge field, with an anti-unitary particle-hole symmetry, precisely the form conjectured recently by Son to be the low-energy description of a particle-hole symmetric half-filled Landau level. Out of these modes, they construct a neutral Dirac fermion coupled to an emergent U(1) gauge field. Gauge invariance requires the existence of gapless edge modes at the interface between the CFL and CHL. The authors construct a particle-hole symmetric theory by studying a system consisting of alternating quasi-one-dimensional strips of composite Fermi liquid (CFL) and composite hole liquid (CHL), both of which break particle-hole symmetry. One then attaches flux to the holes, and the resulting composite hole description is another viable description of the half-filled Landau level. However, an equivalent starting point is one where one starts with a filled Landau level, depletes electrons (or equivalently, adds holes) to the point of half filling. In this theory, composite fermions arise when flux is attached to electrons in a half-filled Landau level. Specifically, they start with the traditional approach to the half-filled Landau level: an effective field theory known as the composite Fermi liquid pioneered by Halperin, Lee, and Read. Here, the authors investigate the possibility that particle-hole symmetry in the lowest Landau level at half filling arises as an emergent low-energy symmetry.
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