English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

Transition metal oxides exhibit various competing phases and exotic phenomenadepending on how their reaction to the rich degeneracy of the $d$-orbital.Large spin-orbit coupling (SOC) reduces this degeneracy in a unique way byproviding a spin-orbital-entangled ground state for 4$d$ and 5$d$ transitionmetal compounds. In particular, the spin-orbital-entangled Kramers doublet,known as the $J_{\mathbf{eff}}$=1/2 pseudospin, appears in layered iridates and$\alpha$-RuCl$_3$, manifesting a relativistic Mott insulating phase. Suchentanglement, however, seems barely attainable in 3$d$ transition metal oxides,where the SOC is small and the orbital angular momentum is easily quenched.From experimental and theoretical evidence, here we report on the CuAl$_2$O$_4$spinel as the first example of a $J_{\mathbf{eff}}$=1/2 Mott insulator in 3$d$transition metal compounds. Based on the experimental study, includingsynthesis of the cubic CuAl$_2$O$_4$ single crystal, density functional theoryand dynamical mean field theory calculations reveal that the$J_{\mathbf{eff}}$=1/2 state survives the competition with anorbital-momentum-quenched $S$=1/2 state. The electron-addition spectra probingunoccupied states are well described by the $j_{\mathbf{eff}}$=1/2 hole state,whereas electron-removal spectra have a rich multiplet structure. The fullyrelativistic entity found in CuAl$_2$O$_4$ provides new insight into theuntapped regime where the spin-orbital-entangled Kramers pair coexists withstrong electron correlation.

Theoretical evidence of spin-orbital-entangled $J_{\mathbf{eff}}$=1/2 state in the 3$d$ transition metal oxide CuAl$_2$O$_4$