A microscopic model of fractionalized Fermi liquid

Abstract

In this short letter we identify a relationship between the Kondo lattice model formulated in Coleman {\it et.al}, Phys. Rev. Lett. {\bf 129}, 177601 (2022) and Ancilla Layer formulation of the Hubbard model recently proposed by Zhang and Sachdev.

Figures (2)

• Figure 1: a.) In the CPT model (1) each site is trivalent, hosting conduction electrons, shown here as black circles, localized spins-1/2 ${\bf S}_1$ linked by Heisenberg exchange and ${\bf S}_2$, linked by color-coded Kitaev interactions. The frustrated Kitaev interactions induce a Majorana fractionalization of spins, which are then Kondo-coupled to the conduction electrons on the same lattice. b.) FL* phase. At large Kondo coupling spins ${\bf S}_1$ are "absorbed" into the electron band contributing to its Luttinger volume. Then spins ${\bf S}_2$ create Kitaev spin liquid - a Majorana thermal metal with a Fermi surface. c.) FL phase. Zero Kondo coupling. The spins do not contribute to the Luttinger volume of the conduction band. They create Yao-Lee spin liquid instead.
• Figure 2: Phase diagram of the CPT model Eq.(1) and Fig. 1a at one electron per site CPT2. In FL$_{1,2}$ phases the spin and electron subsystems are decoupled (Fig. 1c). Below the Kondo temperature $T_K$ they are coupled . At $J <J_c$ the ground state is an exotic (fractionalized) superconductor. At $J>J_c$ the ground state is a fractionalized Fermi liquid FL* (Fig. 1b). The transition lines $T_{c1}, T'_{c1}$ mark phase transitions in, respectively, the Yao-Lee and Kitaev spin liquids. Below these transitions the visons become rare.