Migdal-Eliashberg theory breaks down to polaron/bipolaron states before phonon softening at extreme densities, with variational upper bounds on coupling λ showing this occurs well before softening in 2D/3D systems.
Fractionalized Fermi liquids and the cuprate phase diagram
8 Pith papers cite this work. Polarity classification is still indexing.
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Pith papers citing it
abstract
We review a theoretical framework for the cuprate superconductors, rooted in a fractionalized Fermi liquid (FL*) description of the intermediate-temperature pseudogap phase at low doping. The FL* theory predicted hole pockets each of fractional area $p/8$ at hole doping $p$, in contrast to the area $p/4$ in spin density wave theory. Magnetotransport measurements, including observation of the Yamaji angle, show clear evidence of hole pocket quasiparticles which can tunnel coherently between square lattice layers, and are consistent with the FL* description. The FL* phase of a single-band model is described using a layer construction with a pair of ancilla qubits on each site: the Ancilla Layer Model (ALM). Fluctuations are described by the SU(2) gauge theory of a background spin liquid with critical Dirac spinons. A Monte Carlo study of the thermal SU(2) gauge theory transforms the hole pockets into Fermi arcs in photoemission. One route to confinement of FL* upon lowering temperature yields a $d$-wave superconductor via a Kosterlitz-Thouless transition of $h/(2e)$ vortices, with nodal Bogoliubov quasiparticles featuring anisotropic velocities and vortices surrounded by charge order halos. Increasing doping from the FL* phase in the ALM drives a transition to a conventional Fermi liquid (FL) at large doping, passing through an intermediate strange metal regime. We formulate a theory of the FL*-FL metal-metal transition without a symmetry-breaking order parameter, using a critical quantum `charge' liquid of mobile electrons in the presence of disorder, developed via an extension of the Sachdev-Ye-Kitaev model to two spatial dimensions. At low temperatures, and across optimal and over doping, we address the regimes of extended non-Fermi liquid behavior by Griffiths effects near quantum phase transitions in disordered metals.
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UNVERDICTED 8roles
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In the Holstein model, polaronic and bipolaronic states emerge before phonon softening across wide fillings in 2D and 3D, via an intermediate pseudogap mixed state where Luttinger theorem is broken.
A conserving diagrammatic theory for the doped Hubbard model shows four magnetic polaron hole pockets, doping-softened magnons, and pseudogap-like lattice modulation responses near half filling.
The model has a hybridized phase where spin-liquid Majorana fermions and conduction electrons form a common small Fermi surface violating the Luttinger count, with momentum-dependent coherence factors that produce Fermi arcs.
Inelastic neutron scattering on CeCoIn5 shows spin excitations consistent with fractionalized spinons coexisting with d-wave superconductivity near a quantum critical point.
Monte Carlo study of thermal SU(2) gauge theory with Higgs boson reconciles Fermi arcs and p/8 hole pockets while describing intertwined orders and d-wave superconductivity at lower temperatures.
Identifies a relationship between the Kondo lattice model and the ancilla layer Hubbard model as a microscopic realization of the fractionalized Fermi liquid.
The fractionalized Fermi liquid state obtained by doping quantum spin liquids resolves key experimental difficulties in cuprate pseudogap metals and d-wave superconductors.
citing papers explorer
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Breakdown of the Migdal-Eliashberg theory for electron-phonon systems. Role of polarons/bi-polarons
Migdal-Eliashberg theory breaks down to polaron/bipolaron states before phonon softening at extreme densities, with variational upper bounds on coupling λ showing this occurs well before softening in 2D/3D systems.
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Limits of validity for Migdal-Eliashberg theory: role of polarons/bi-polarons
In the Holstein model, polaronic and bipolaronic states emerge before phonon softening across wide fillings in 2D and 3D, via an intermediate pseudogap mixed state where Luttinger theorem is broken.
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Hole and spin dynamics in an anti-ferromagnet close to half filling
A conserving diagrammatic theory for the doped Hubbard model shows four magnetic polaron hole pockets, doping-softened magnons, and pseudogap-like lattice modulation responses near half filling.
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Tractable model for a fractionalized Fermi liquid (FL$^*$) on a square lattice
The model has a hybridized phase where spin-liquid Majorana fermions and conduction electrons form a common small Fermi surface violating the Luttinger count, with momentum-dependent coherence factors that produce Fermi arcs.
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Superconductivity and fractionalized magnetic excitations in CeCoIn5
Inelastic neutron scattering on CeCoIn5 shows spin excitations consistent with fractionalized spinons coexisting with d-wave superconductivity near a quantum critical point.
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Thermal SU(2) lattice gauge theory for intertwined orders and hole pockets in the cuprates
Monte Carlo study of thermal SU(2) gauge theory with Higgs boson reconciles Fermi arcs and p/8 hole pockets while describing intertwined orders and d-wave superconductivity at lower temperatures.
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A microscopic model of fractionalized Fermi liquid
Identifies a relationship between the Kondo lattice model and the ancilla layer Hubbard model as a microscopic realization of the fractionalized Fermi liquid.
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Lectures on insulating and conducting quantum spin liquids
The fractionalized Fermi liquid state obtained by doping quantum spin liquids resolves key experimental difficulties in cuprate pseudogap metals and d-wave superconductors.