Can Orbital-Selective N\'eel Transitions Survive Strong Nonlocal Electronic Correlations?

TL;DR

This paper explores the possibility of realizing orbital-selective Ne9el transitions in correlated electron systems, emphasizing the role of nonlocal correlations and the absence of Hund's coupling, with implications for spin-orbitronics.

Contribution

It demonstrates that orbital-selective Ne9el transitions can occur across different coupling regimes, revealing a non-trivial intermediate regime influenced by the interplay of Slater and Heisenberg mechanisms.

Findings

Orbital-selective Ne9el transitions are possible without Hund's exchange.

The transition mechanism varies from Slater to Heisenberg depending on coupling strength.

A non-trivial intermediate regime exhibits unique orbital-selective magnetic ordering.

Abstract

Spin- or orbital-selective behaviours in correlated electron materials offer rich promise for spintronics or orbitronics phenomena and applications deriving from them. Strong local electronic Coulomb correlations might lead to an orbital-selective Mott state, characterised by the coexistence of localized electrons in some orbitals with itinerant electrons in others. Nonlocal electronic fluctuations are much more entangled in orbital space than the local ones. For this reason, finding orbital-selective phenomena related to nonlocal correlations, such as orbital-selective magnetic transitions, is a challenge. In this work we investigate possibilities to realize an orbital-selective N\'eel transition (OSNT). We illustrate that stabilising this state requires a decoupling of magnetic fluctuations in different orbitals, which can only be realized in the absence of Hund's exchange coupling. On the basis of two-orbital calculations for a Hubbard model with different bandwidths we show that the proposed OSNT can be found all the way from the weak to the strong coupling regime. In the weak coupling regime the transition is governed by a Slater mechanism and thus occurs first for the narrow orbital. At strong coupling a Heisenberg mechanism of the OSNT sets in, and the transition occurs first for the wide orbital. Remarkably, at intermediate values of the interaction we find a non-trivial regime of the OSNT, where the Slater mechanism leads to a N\'eel transition occurring first for the wide orbital. Our work suggests strategies for searching for orbital-selective N\'eel ordering in real materials, in view of possible spin-orbitronics applications.