Probing spin correlations using angle-resolved photoemission in a coupled metallic/Mott insulator system

Abstract

T.O.), Andy.Mackenzie@cpfs.mpg.de (A.P.M.), philip.king@st-andrews.ac.uk (P.D.C.K.) † These authors contributed equally to this work.Abstract: A nearly free electron metal and a Mott insulating state can be thought of as opposite ends of possibilities for the motion of electrons in a solid. In the magnetic oxide metal PdCrO 2 , these two coexist as alternating layers. Using angle resolved photoemission, we surprisingly find sharp band-like features in the one-electron removal spectral function of the correlated subsystem. We show that these arise because a hole created in the Mott layer moves to and propagates in the metallic layer while retaining memory of the Mott layer's magnetism. This picture is quantitatively supported by a strong coupling analysis capturing the physics of PdCrO 2 in terms of a Kondo lattice Hamiltonian. Our findings open new routes to use the non-magnetic probe of photoemission to gain insights into the spin-susceptibility of correlated electron systems.One Sentence Summary: An intrinsically non-magnetic spectroscopy is shown to have strong magnetic sensitivity in Kondo-coupled PdCrO 2 .Main Text: PdCrO 2 is a member of the broad class of layered triangular lattice materials whose layer stacking sequence (see Fig. 1A) is that of the delafossite structural family ABO 2 (1). In a simple ionic picture of the delafossites, triangular co-ordinated layers of A + ions are stacked between BO 2 octahedra in which the B ions also have triangular co-ordination (2, 3). Most delafossites are insulating or semiconducting. PdCoO 2 and PtCoO 2 , however, are extremely high

Unconventional magnetism and electronic state in the frustrated layered system PdCrO2

“…Previous DFT calculation of exchange parameters reported in Ref. [31] unfortunately did not take into account strong Coulomb correlations, which were recently shown to be important for PdCrO 2 [9,10]. Also, only two in-plane isotropic exchange parameters were calculated there, namely, between the nearest and next-nearest neighbors.…”

“…According to Ref. [9], weak binding energy dependence and the Cr character of the reconstructed weight indicate that the spectroscopic properties of PdCrO 2 are essentially determined by a Kondo coupling of nearly free electrons in metallic layers, with localized electrons in a Mott insulating state in adjacent layers. Thus, the system can be described by the Anderson lattice model (or s − d exchange model, which corresponds to the case where d states are not close to the Fermi level).…”

“…However, the situation can be more complicated. First, in a very recent spectroscopic study [9], strong enough hybridization between Cr d − sites and metallic electrons of Pd has been observed. Also, first-principles dynamical mean-field theory (DMFT) calculations [10] show that, despite that the Cr d − electron subsystem is strongly correlated and lies on the insulating side of Mott transition, they are pretty far from the atomic limit assumed in Refs.…”

Quasiparticle interference and quantum confinement in a correlated Rashba spin-split 2D electron liquid

“…The coherence length is substantially larger than the spin precession length, making this a promising system for spintronic applications. On a broader perspective, atomic-scale studies of the transition metal oxide terminations of other delafossites provide an opportunity to study the interplay between ISB, SOC, electronic correlations, and magnetic order ( 32 ).…”

Hidden order and multipolar exchange striction in a correlated f -electron system

“…We subsequently employed the FT-HI method ( 38 ) to evaluate all SEIs between the quadruplet for several first Np–Np coordination shells. Previously, the FT-HI method was applied to systems with conventional magnetic primary order ( 52 , 57 ). Within this method, matrix elements of intersite coupling for the Np–Np bond read where is the corresponding element of the density matrix on site , is the derivative of atomic (HI) self-energy over a fluctuation of the element, and is the intersite Green’s function for the Np–Np bond evaluated within the DFT + HI.…”