Magnetic field induced intermediate gapless spin-liquid phase with a spinon Fermi surface*

Quantum spin liquids have generated considerable excitement in the condensed matter physics community. We employ the density matrix renormalization group to study the Kitaev model with a magnetic field in the H∥[111] direction. We show the presence of an intermediate phase, between the gapped Kitaev spin liquid and partially field polarized phase, that is a candidate spin liquid. We show that the spin-spin correlations in real-space obey power-law decay that is indicative of gapless spin excitations. Additionally, we present calculations of specific heat, entropy, and spin susceptibility at the finite temperature to provide further evidence of a gapless phase. Using the peaks of spin structure factor, we propose an existence of a spinon Fermi surface in the intermediate phase.