Majorana Fermi surface state in a network of quantum spin chains

Fabrizio Oliviero^1,2*, Weslei B. Fontana², Rodrigo G. Pereira³

¹Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan
²Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
³Department of Physics, Universidade Federal do Rio Grande do Norte, Natal/RN, Brazil

* Presenter:Fabrizio Oliviero, email:fabrizio@phys.ncts.ntu.edu.tw

In general, quantum spin liquids describe systems where effective degrees of freedom are represented by localized magnetic moments on a lattice, which lack long-range order even at very low temperatures. These systems are characterized by ground-state wave functions with substantial entanglement and excitations that exhibit fractionalization. This work specifically examines chiral spin liquids arising in Mott insulators that break both time-reversal and parity symmetry. Starting from critical spin-1 chain junctions, we construct a honeycomb network that supports a chiral spin liquid with a gapless spectrum. The low-energy excitations are spin-1 Majorana fermions, which yield a genuine two-dimensional state with a Fermi surface when the junction interactions are tuned near chiral fixed points with staggered chirality. We analyze the physical properties and robustness of the chiral spin liquid phase in response to boundary perturbations, using controlled analytical approaches within the network's effective field theory framework. Finally, we connect our findings to previous mean-field studies within the parton framework.

Keywords: spin-1 chains, network construction, Majorana Fermi surface