Gapless state of interacting Majorana fermions in a strain-induced Landau level

Abstract

Mechanical strain can generate a pseudomagnetic field, and hence Landau levels (LL), for low-energy excitations of quantum matter in two dimensions. We study the collective state of the fractionalized Majorana fermions arising from residual generic spin interactions in the central LL, where the projected Hamiltonian reflects the spin symmetries in intricate ways: emergent U(1) and particle-hole symmetries forbid any bilinear couplings, leading to an intrinsically strongly interacting system; also, they allow the definition of a filling fraction, which is fixed at 1/2. We argue that the resulting many-body state is gapless within our numerical accuracy, implying ultra-short-ranged spin correlations, while chirality correlators decay algebraically. This amounts to a Kitaev 'non-Fermi' spin liquid and shows that interacting Majorana Fermions can exhibit intricate behavior akin to fractional quantum Hall physics in an insulating magnet.