Hidden Mott insulator in metallic PdCrO2

Abstract

There has been a long-standing debate on the coexistence between itinerant electrons and localized spins in the PdCrO2 delafossite. By means of the charge self-consistent combination of density functional theory and dynamical mean-field theory, it is corroborated that despite overall remarkable metallic response, the CrO2 layers are indeed Mott insulating as suggested by previous experimental work. The resulting k-resolved spectral function in the paramagnetic phase is in excellent agreement with available photoemission data. Subtle coupling between the itinerant and Mott-localized degrees of freedom is revealed. Different doping scenarios are simulated in order to manipulate the electronic states within the inert layers. In particular, oxygen vacancies prove effective in turning the hidden Mott insulator into a strongly correlated itinerant subsystem. The present results may open a new venue in research on quantum materials beyond canonical classification schemes. Pd O Cr c−axis FIG. 1. (color online) Delafossite ABO2 crystal structure exemplified for PdCrO2 with Pd (grey), Cr (blue) and O (red).arXiv:1805.01738v3 [cond-mat.str-el]

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

“…Apart from this, however, our calculated spectral function is in excellent agreement with that obtained in Ref. (20) using a numerically exact quantum Monte Carlo method (one may notice a rather weak lifetime broadening for the occupied part of , shown in Fig. 3 of Ref.…”

Theoretical design of highly correlated electron states in delafossite heterostructures

“…The cPd dispersion is dominantly formed by a linear combination of in-plane d x 2 −y 2 and d xy , as well as by some d z 2 contribution (see Ref. 10 for more details). Note that the kintegrated projected spectral function A proj (ω) still displays sizable Cr-weight at low energy, associated with the cPd band.…”

“…presents a summary of the spectral characteristics. For PdCrO 2 , local Coulomb interactions on the chromium site of U = 3 eV and J H = 0.7 eV prove adequate as discussed in Ref 10…”

“…Among these fascinating materials, the PdCrO 2 compound stands further out as it unites high metallicity from the Pd + (4d 9 ) planes with Mott-insulating CrO 2 layers [8][9][10][11] . Replacing Pd by neighboring Ag formally leads to a closed 4d 10 shell and nonsurprisingly, AgCrO 2 is indeed insulating with a technologically interesting band gap of 1.68 eV 5 .…”

Unconventional magnetism and electronic state in the frustrated layered system PdCrO2

“…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. [5,6].…”