Tractable model for a fractionalized Fermi liquid (FL $^*$ ) on a square latticeTractable model for a fractionalized Fermi liquid (FL$^*$) on a square lattice

Piers Coleman, Elio J. König, Aaditya Panigrahi +1 more

Motivated by the continued interest in Fermi-surface reconstruction without symmetry breaking, we present an analytically tractable microscopic model of a fractionalized Fermi liquid (FL $^*$ ) on a square lattice and discuss its potential relevance to the cuprates. As in ancilla-qubit constructions, the model is related to Kondo lattice systems, but in this case, the conduction electrons interact with a $\mathbb{Z}_2$ spin liquid of the Yao--Lee type, with a Majorana Fermi surface. The associated $\mathbb Z_2$ gauge theory is static so that the model can be analytically solved to leading-logarithic accuracy. There are two phases: one in which the fractionalized fermions of the spin liquid hybridize with conduction electrons to form a common Fermi surface violating the naive Luttinger count, and one in which they remain decoupled. We discuss the salient features of the small Fermi-surface phase, including analytically derived momentum dependent coherence factors responsible for the appearance of Fermi arcs à la Yang-Rice-Zhang. We further discuss the impact of quantum and thermal fluctuations, including a strong diamagnetic response and a logarithmically divergent Sommerfeld coefficient at the onset of the pseudogap.Motivated by the continued interest in Fermi-surface reconstruction without symmetry breaking, we present an analytically tractable microscopic model of a fractionalized Fermi liquid (FL$^*$) on a square lattice and discuss its potential relevance to the cuprates. As in ancilla-qubit constructions, the model is related to Kondo lattice systems, but in this case, the conduction electrons interact with a $\mathbb{Z}_2$ spin liquid of the Yao--Lee type, with a Majorana Fermi surface. The associated $\mathbb Z_2$ gauge theory is static so that the model can be analytically solved to leading-logarithic accuracy. There are two phases: one in which the fractionalized fermions of the spin liquid hybridize with conduction electrons to form a common Fermi surface violating the naive Luttinger count, and one in which they remain decoupled. We discuss the salient features of the small Fermi-surface phase, including analytically derived momentum dependent coherence factors responsible for the appearance of Fermi arcs à la Yang-Rice-Zhang. We further discuss the impact of quantum and thermal fluctuations, including a strong diamagnetic response and a logarithmically divergent Sommerfeld coefficient at the onset of the pseudogap.

arXiv:2604.06157Apr 7, 20260 citations

The Fractionalized Fermi Liquid

Subir Sachdev A

Cambridge University Press eBooksMar 24, 20230 citations

Fractionalized Fermi liquids in a quantum dimer model

Junhyun Lee, Steven White, Subir Sachdev A

Bulletin of the American Physical SocietyMar 18, 20160 citations

Large-Nlimit of the square-latticet-Jmodel at (1/4 and other filling fractions

Subir Sachdev A

We present a mean-field theory of the t-J model on a square lattice that becomes exact in a particular large-N limit. A detailed study of the free-energy manifold is carried out for the case of filling fraction \ensuremath{\nu}=(1/4 as a function of t/J. Over the manifold examined, the ground state is either an insulating crystal of an N-hole bound state (for small t/J) or a normal Fermi liquid (for large t/J). For (1/4\ensuremath{\le}\ensuremath{\nu}\ensuremath{\le} 1) / 2 , and t= ${0}^{+}$ , states with the localized holes, and nonzero spin correlations restricted to clusters of 4 or smaller, are global free-energy minima; in particular they are lower in energy than the state with uniform flux \ensuremath{\Phi}=\ensuremath{\nu}, with staggered flux or a normal Fermi liquid.We present a mean-field theory of the t-J model on a square lattice that becomes exact in a particular large-N limit. A detailed study of the free-energy manifold is carried out for the case of filling fraction \ensuremath{\nu}=(1/4 as a function of t/J. Over the manifold examined, the ground state is either an insulating crystal of an N-hole bound state (for small t/J) or a normal Fermi liquid (for large t/J). For (1/4\ensuremath{\le}\ensuremath{\nu}\ensuremath{\le} 1) / 2 , and t=${0}^{+}$, states with the localized holes, and nonzero spin correlations restricted to clusters of 4 or smaller, are global free-energy minima; in particular they are lower in energy than the state with uniform flux \ensuremath{\Phi}=\ensuremath{\nu}, with staggered flux or a normal Fermi liquid.

Physical review. B, Condensed matterMar 1, 199020 citations

Fractionalized Fermi liquids and exotic superconductivity in the Kitaev-Kondo lattice

Urban F. P. Seifert, Tobias Meng, Matthias Vojta C

Fractionalized Fermi liquids ( ${\mathrm{FL}}^{*}$ ) have been introduced as non-Fermi-liquid metallic phases, characterized by coexisting electron-like charge carriers and local moments which form a fractionalized spin liquid. Here we investigate a Kondo lattice model on the honeycomb lattice with Kitaev interactions among the local moments, a concrete model hosting ${\mathrm{FL}}^{*}$ phases based on Kitaev's ${\mathbb{Z}}_{2}$ spin liquid. We characterize the ${\mathrm{FL}}^{*}$ phases via perturbation theory, and we employ a Majorana-fermion mean-field theory to map out the full phase diagram. Most remarkably we find nematic triplet superconducting phases which mask the quantum phase transition between fractionalized and conventional Fermi liquid phases. Their pairing structure is inherited from the Kitaev spin liquid; i.e., superconductivity is driven by Majorana glue.Fractionalized Fermi liquids (${\mathrm{FL}}^{*}$) have been introduced as non-Fermi-liquid metallic phases, characterized by coexisting electron-like charge carriers and local moments which form a fractionalized spin liquid. Here we investigate a Kondo lattice model on the honeycomb lattice with Kitaev interactions among the local moments, a concrete model hosting ${\mathrm{FL}}^{*}$ phases based on Kitaev's ${\mathbb{Z}}_{2}$ spin liquid. We characterize the ${\mathrm{FL}}^{*}$ phases via perturbation theory, and we employ a Majorana-fermion mean-field theory to map out the full phase diagram. Most remarkably we find nematic triplet superconducting phases which mask the quantum phase transition between fractionalized and conventional Fermi liquid phases. Their pairing structure is inherited from the Kitaev spin liquid; i.e., superconductivity is driven by Majorana glue.

arXiv:1710.09381Physical review. B./Physical review. BFeb 12, 201840 citations

Tractable model for a fractionalized Fermi liquid (FL

^*

) on a square lattice

Motivated by the continued interest in Fermi-surface reconstruction without symmetry breaking, we present an analytically tractable microscopic model of a fractionalized Fermi liquid (FL

^*

) on a square lattice and discuss its potential relevance to the cuprates. As in ancilla-qubit constructions, the model is related to Kondo lattice systems, but in this case, the conduction electrons interact with a

\mathbb{Z}_2

spin liquid of the Yao--Lee type, with a Majorana Fermi surface. The associated

\mathbb Z_2

gauge theory is static so that the model can be analytically solved to leading-logarithic accuracy. There are two phases: one in which the fractionalized fermions of the spin liquid hybridize with conduction electrons to form a common Fermi surface violating the naive Luttinger count, and one in which they remain decoupled. We discuss the salient features of the small Fermi-surface phase, including analytically derived momentum dependent coherence factors responsible for the appearance of Fermi arcs à la Yang-Rice-Zhang. We further discuss the impact of quantum and thermal fluctuations, including a strong diamagnetic response and a logarithmically divergent Sommerfeld coefficient at the onset of the pseudogap.

{0}^{+}

, states with the localized holes, and nonzero spin correlations restricted to clusters of 4 or smaller, are global free-energy minima; in particular they are lower in energy than the state with uniform flux \ensuremath{\Phi}=\ensuremath{\nu}, with staggered flux or a normal Fermi liquid.

Fractionalized Fermi liquids (

{\mathrm{FL}}^{*}

) have been introduced as non-Fermi-liquid metallic phases, characterized by coexisting electron-like charge carriers and local moments which form a fractionalized spin liquid. Here we investigate a Kondo lattice model on the honeycomb lattice with Kitaev interactions among the local moments, a concrete model hosting

{\mathrm{FL}}^{*}

phases based on Kitaev's

{\mathbb{Z}}_{2}

spin liquid. We characterize the

{\mathrm{FL}}^{*}

phases via perturbation theory, and we employ a Majorana-fermion mean-field theory to map out the full phase diagram. Most remarkably we find nematic triplet superconducting phases which mask the quantum phase transition between fractionalized and conventional Fermi liquid phases. Their pairing structure is inherited from the Kitaev spin liquid; i.e., superconductivity is driven by Majorana glue.