We study a two-flavor fermion model where each of the flavors form a Sachdev-Ye-Kitaev (SYK) system with arbitrary $q$ -body interactions. The crucial new element is an all-to-all $r$ -body interaction between the two flavors. At high temperatures, the model shows a strange metal phase where both flavors are gapless, similar to the usual single-flavor SYK model. Upon reducing temperature, the coupled system undergoes transitions to previously unseen phases in the SYK framework---first, a strange half-metal phase where one flavor remains a strange metal while the other is gapped, and second, an insulating phase of the Mott kind where both flavors are gapped. At a fixed low temperature, we obtain transitions between these phases by tuning the relative fraction of sites for each flavor. We discuss the physics of these phases and the nature of transitions between them. This work provides an example of an instability of the strange metal with potential to provide new routes to study strongly correlated systems through the rich physics contained in SYK-like models.We study a two-flavor fermion model where each of the flavors form a Sachdev-Ye-Kitaev (SYK) system with arbitrary $q$-body interactions. The crucial new element is an all-to-all $r$-body interaction between the two flavors. At high temperatures, the model shows a strange metal phase where both flavors are gapless, similar to the usual single-flavor SYK model. Upon reducing temperature, the coupled system undergoes transitions to previously unseen phases in the SYK framework---first, a strange half-metal phase where one flavor remains a strange metal while the other is gapped, and second, an insulating phase of the Mott kind where both flavors are gapped. At a fixed low temperature, we obtain transitions between these phases by tuning the relative fraction of sites for each flavor. We discuss the physics of these phases and the nature of transitions between them. This work provides an example of an instability of the strange metal with potential to provide new routes to study strongly correlated systems through the rich physics contained in SYK-like models.

arXiv:1703.05111Physical review. B./Physical review. BOct 24, 201821 citations

Theory of Strange Metals from Hot Fermions

Connie H. Mousatov, Erez Berg, Sean A. Hartnoll

Bulletin of the American Physical SocietyMar 4, 20190 citations

Theory of Strange Metals from Hot Fermions

Erez Berg, Sean A. Hartnoll, Connie H. Mousatov

arXiv:1810.12945Oct 30, 20181 citation

Strange metals and black holes: insights from the Sachdev-Ye-Kitaev model

Subir Sachdev A

Complex many-particle quantum entanglement is a central theme in two distinct major topics in physics: the strange metal state found in numerous correlated electron compounds, and the quantum theory of black holes in Einstein gravity. The Sachdev-Ye-Kitaev model provides a solvable theory of entangled many-particle quantum states without quasiparticle excitations. This article reviews how this toy model has led to realistic universal models of strange metals, and to new insights on the quantum states of black holes.Complex many-particle quantum entanglement is a central theme in two distinct major topics in physics: the strange metal state found in numerous correlated electron compounds, and the quantum theory of black holes in Einstein gravity. The Sachdev-Ye-Kitaev model provides a solvable theory of entangled many-particle quantum states without quasiparticle excitations. This article reviews how this toy model has led to realistic universal models of strange metals, and to new insights on the quantum states of black holes.

arXiv:2305.01001May 1, 20230 citations

Thermoelectric transport in disordered metals without quasiparticles: The Sachdev-Ye-Kitaev models and holography

Richard A. Davison, Wenbo Fu, Antoine Georges +3 more

Essentially all high temperature superconductors display a ``strange metal'' regime above their critical temperatures, where electrical and thermal transport cannot be explained within the traditional Fermi liquid paradigm of quasiparticle excitations. This paper focuses on the first, and newly discovered, solvable theory of a disordered metal without quasiparticle excitations, obtained by extending the Sachdev-Ye-Kitaev (SYK) models to finite spatial dimensions. The complete thermoelectric conductivity matrix is computed, and a surprising exact relation is found between the Seebeck coefficient and the derivative of the thermodynamic entropy with respect to the density. These computations are then compared with holographic theories which map strange metals onto black holes in theories of quantum gravity with one extra spatial dimension.Essentially all high temperature superconductors display a ``strange metal'' regime above their critical temperatures, where electrical and thermal transport cannot be explained within the traditional Fermi liquid paradigm of quasiparticle excitations. This paper focuses on the first, and newly discovered, solvable theory of a disordered metal without quasiparticle excitations, obtained by extending the Sachdev-Ye-Kitaev (SYK) models to finite spatial dimensions. The complete thermoelectric conductivity matrix is computed, and a surprising exact relation is found between the Seebeck coefficient and the derivative of the thermodynamic entropy with respect to the density. These computations are then compared with holographic theories which map strange metals onto black holes in theories of quantum gravity with one extra spatial dimension.

arXiv:1612.00849Physical review. B./Physical review. BApr 18, 2017435 citations

We study a two-flavor fermion model where each of the flavors form a Sachdev-Ye-Kitaev (SYK) system with arbitrary

q

-body interactions. The crucial new element is an all-to-all

r

-body interaction between the two flavors. At high temperatures, the model shows a strange metal phase where both flavors are gapless, similar to the usual single-flavor SYK model. Upon reducing temperature, the coupled system undergoes transitions to previously unseen phases in the SYK framework---first, a strange half-metal phase where one flavor remains a strange metal while the other is gapped, and second, an insulating phase of the Mott kind where both flavors are gapped. At a fixed low temperature, we obtain transitions between these phases by tuning the relative fraction of sites for each flavor. We discuss the physics of these phases and the nature of transitions between them. This work provides an example of an instability of the strange metal with potential to provide new routes to study strongly correlated systems through the rich physics contained in SYK-like models.