Impact of multiband effects on non-Fermi-liquid transport phenomena in bilayer nickelates

Summary

This study employs a multi-orbital tight-binding model to analyze non-Fermi liquid transport phenomena in the bilayer nickelate La₃Ni₂O₇, focusing on the influence of multiband effects on the Hall coefficient. Using the Green's function method, a rigorous formula for the Hall coefficient incorporating the quasi-quantum metric (qQM) term is derived, revealing that the temperature dependence of this qQM term is crucial in strongly correlated multiband systems. Calculations show that spin fluctuations in the Ni d₂² orbital lead to stronger quasiparticle damping, while the Ni d_x²_-y² orbital forms cold spots. The pronounced temperature dependence of the Hall coefficient in La₃Ni₂O₇ originates from the competition between the positive contribution of the hole band and the negative contribution of the electron band, with the qQM term enhancing the positive Hall coefficient at low temperatures and explaining the experimentally observed T-linear resistivity and the increase of the Hall coefficient upon cooling. Furthermore, the qQM term also plays a key role in describing the Nernst coefficient and other transport phenomena involving second derivatives of velocity. This study reveals the core mechanism of spin-fluctuation-induced orbital-selective renormalization in non-Fermi liquid transport, providing a theoretical framework for understanding the anomalous transport properties of this system.

Materials

• La₃Ni₂O₇

Methods

• Multi-orbital tight-binding model
• Fluctuation-exchange approximation (FLEX)
• Green's function method
• Linear response theory

Keywords

• non fermi liquid transport
• t linear resistivity
• hall coefficient
• quasi quantum metric
• cold spots
• spin fluctuations
• orbital selective renormalization

Highlights

• First derivation of a rigorous formula for the Hall coefficient including many-body qQM effects in strongly correlated multiband systems.
• Explains both T-linear resistivity and the increasing positive Hall coefficient at low temperatures in thin-film bilayer nickelates.

Conclusions

• Spin fluctuations cause stronger quasiparticle damping in the Ni dz2 orbital, leading to cold spots on the Ni dx2-y2 orbital.
• Derived a rigorous formula for the Hall coefficient incorporating the many-body quasi-quantum metric (qQM) term; the temperature dependence of the qQM term is crucial for determining RH.
• The temperature dependence of RH arises from competition between positive hole band and negative electron band contributions; the qQM term enhances positive RH at low temperatures, explaining experimental observations.

Main claims

• The temperature dependence of the Hall coefficient in La₃Ni₂O₇ is dominated by the quasi-quantum metric term, which becomes significant due to strong orbital-dependent quasiparticle damping.
  • Evidence: Derived rigorous formula for Hall coefficient with qQM term; calculations show qQM term enhances positive contribution at low T
• Spin fluctuations cause stronger quasiparticle damping in the d_z² orbital, while dx²-y² forms cold spots, leading to orbital-selective transport.
  • Evidence: FLEX self-energy calculations show larger ImΣ for d_z² than dx²-y²; cold spots appear on α and β FSs where dx²-y² weight dominates
• The competition between hole and electron pockets, together with the qQM term, explains the observed T-linear resistivity and positive Hall coefficient increasing at low temperatures.
  • Evidence: Calculated ρxx shows linear T dependence; R_H positive and increases at low T; matches experimental data from Ref. 1,4

Workflow

• model_construction — Realistic tight-binding model for thin-film La₃Ni₂O₇.
  • Materials: thin-film La₃Ni₂O₇
  • Methods: multiorbital tight-binding model from DFT; modification to match ARPES
  • Observations: three Fermi surfaces: α, β, γ; cold spots near X point
• flex_calculation — Orbital-selective quasiparticle damping due to spin fluctuations.
  • Materials: tight-binding model
  • Methods: fluctuation exchange approximation; self-energy calculation
  • Observations: spin fluctuations cause larger quasiparticle damping in d_z² orbital; dx²-y² forms cold spots
• transport_calculation — Non-Fermi-liquid transport phenomena reproduced.
  • Materials: self-energy from FLEX
  • Methods: linear response theory with qQM formula for Hall coefficient
  • Observations: T-linear resistivity; positive Hall coefficient that increases at low T; negative Nernst coefficient