The properties of ultrapure delafossite metals

Abstract

Although they were first synthesized in chemistry laboratories nearly fifty years ago, the physical properties of the metals PdCoO2, PtCoO2 and PdCrO2 have only more recently been studied in detail. The delafossite structure contains triangular co-ordinated atomic layers, and electrical transport in the delafossite metals is strongly two-dimensional. Their most notable feature is their in-plane conductivity, which is amazingly high for oxide metals. At room temperature, the conductivity of non-magnetic PdCoO2 and PtCoO2 is higher per carrier than those of any alkali metal and even the most conductive elements, copper and silver. At low temperatures the best crystals have resistivities of a few nΩcm, corresponding to mean free paths of tens of microns. PdCrO2 is a frustrated antiferromagnetic metal, with magnetic scattering contributing to the resistivity at high temperatures and small gaps opening in the Fermi surface below the Néel temperature. There is good evidence that electronic correlations are weak in the Pd/Pt layers but strong in the Co/Cr layers; indeed the Cr layer in PdCrO2 is thought to be a Mott insulator. The delafossite metals therefore act like natural heterostructures between strongly correlated and nearly free electron sub-systems. Combined with the extremely high conductivity, they provide many opportunities to study electrical transport and other physical properties in new regimes. The purpose of this review is to describe current knowledge of these fascinating materials and set the scene for what is likely to be a considerable amount of future research.

References in corpus (8)

• Unconventional Anomalous Hall Effect in the Metallic Triangular-Lattice Magnet PdCrO2
• Critical behavior of the metallic triangular-lattice Heisenberg antiferromagnet PdCrO2
• On the metallic conductivity of the delafossites PdCoO2 and PtCoO2
• Magnetic structure of the conductive triangular-lattice antiferromagnet PdCrO2
• Exceptional type-I superconductivity of the layered silver oxide Ag${}_5$Pb${}_2$O${}_6$
• Large anisotropic thermal conductivity of intrinsically two-dimensional metallic oxide PdCoO${}_2$
• Cascade of field-induced magnetic transitions in a frustrated antiferromagnetic metal
• Interplay between localized and itinerant d electrons in a frustrated metallic antiferromagnet, 2H-AgNiO2

Cited by in corpus (48)

• Electronic structure of quantum materials studied by angle-resolved photoemission spectroscopy
• Maximal Rashba-like spin splitting via kinetic energy-driven inversion symmetry breaking
• Unconventional aspects of electronic transport in delafossite oxides
• Yb delafossites: unique exchange frustration of 4f spin 1/2 moments on a perfect triangular lattice
• Directional ballistic transport in the two-dimensional metal PdCoO2
• Electron hydrodynamics with a polygonal Fermi surface
• Evidence of a coupled electron-phonon liquid in NbGe${}_2$
• From basic properties to the Mott design of correlated delafossites
• Field-induced compensation of magnetic exchange as the possible origin of reentrant superconductivity in UTe${}_2$
• The planar triangular $S=3/2$ magnet AgCrSe${}_2$: magnetic frustration, short range correlations, and field tuned anisotropic cycloidal magnetic order
• Nonreciprocal transport in a Rashba ferromagnet, delafossite PdCoO${}_2$
• Growth of CuFeO${}_2$ Single Crystals by the Optical Floating-Zone Technique
• Quasiparticle interference and quantum confinement in a correlated Rashba spin-split 2D electron liquid
• Tuneable electron-magnon coupling of ferromagnetic surface states in PdCoO${}_2$
• Low-symmetry non-local transport in microstructured squares of delafossite metals
• Electrons in helical magnetic field: a new class of topological metals
• Metallic delafossite thin films for unique device applications
• Para-hydrodynamics from weak surface scattering in ultraclean thin flakes
• Stripe magnetic order and field-induced quantum criticality in the perfect triangular-lattice antiferromagnet CsCeSe${}_2$
• Quasi two-dimensional Fermi surface topography of the delafossite PdRhO${}_2$
• Molecular beam epitaxy growth of the highly conductive oxide SrMoO${}_3$
• Avoided metallicity in a hole-doped Mott insulator on a triangular lattice
• Unraveling the unusually high electrical conductivity of the delafossite metal PdCoO${}_2$
• Investigation of Planckian behavior in a high-conductivity oxide: PdCrO${}_2$
• Emergent magnetism with continuous control in the ultrahigh conductivity layered oxide PdCoO2
• Effective reduction of PdCoO2 thin films via hydrogenation and sign tunable anomalous Hall effect
• Bloch-Lorentz magnetoresistance oscillations in delafossites
• Fully two-dimensional incommensurate charge modulation on the Pd-terminated polar surface of PdCoO2
• Probing hidden Mott gap and incommensurate charge modulation on the polar surfaces of PdCrO${}_2$
• Universal superdiffusive modes in charged two dimensional liquids
• $T-$linear resistivity from magneto-elastic scattering: application to PdCrO${}_2$
• Heisenberg spins on an anisotropic triangular lattice: PdCrO2 under uniaxial stress
• Adsorbate-induced formation of a surface-polarity-driven nonperiodic superstructure
• Intermediate-scale theory for electrons coupled to frustrated local-moments
• Diffusion-assisted molecular beam epitaxy of CuCrO${}_2$ thin films
• Anomalous Hall effect in electrolytically reduced PdCoO${}_2$ thin films
• Concurrence of directional Kondo transport and incommensurate magnetic order in the layered material AgCrSe${}_2$
• Dichotomy of electron-phonon interactions in the delafossite PdCoO${}_2$: From weak bulk to polaronic surface coupling
• Disorder-enhanced effective masses and deviations from Matthiessen's rule in PdCoO${}_2$ thin films
• Multipolar Fermi Surface Deformations in Sr${}_2$RuO${}_4$ Probed by Resistivity and Sound Attenuation: A Window into Electron Viscosity and the Collision Operator
• Universality in Non-Equilibrium Quantum Systems
• Novel electronic state of honeycomb iridate Cu${}_2$IrO${}_3$ at high pressure
• Control of Impurity Phase Segregation in a PdCrO${}_2$/CuCrO${}_2$ Heterostructure
• Topological bands in metals
• Layer-Resolved Many-Electron Interactions in Delafossite PdCoO2 from Standing-Wave Photoemission Spectroscopy
• Revisiting the metal-to-metal transition in $2H$-AgNiO${}_2$
• Twin-domain formation in epitaxial triangular lattice delafossites
• Electron-phonon origins of unconventional resistivity in moderately correlated perovskite oxides