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Synergistic Jahn-Teller and Spin-Orbit Effects in a transition metal oxide

Researchers are exploring how quantum properties, like spin-orbit entanglement, emerge in materials. While this is well-studied in heavier metals (4d and 5d), it’s harder in lighter 3d metals because their spin-orbit interactions are weaker. This study shows how an electronic-driven structural effect, called the Jahn-Teller effect, can bridge this gap by enhancing spin-orbit entanglement. These findings reveal new ways to connect material’s spin, orbital, and lattice properties, offering insights into exploring quantum phenomena involving different degrees of freedom in solids.

Spin-orbit states have their orbital part (texture and color) intertwined with the spins (arrows up/down). When they are mixed (bottom), the spin-orbit mixing is detected at optical frequencies by polarized light. | Image by M. Àngels Vilella (Complete image below)

What is spin-orbit coupling?

In a solid, electrons have several degrees of freedom. They occupy orbitals with different energies and spatial distributions, which determine how they move through the crystal. This motion affects their spin due to relativistic effects, where the electrons perceive an effective magnetic field in their rest frame. This interaction is known as spin-orbit coupling, where the electron’s orbital motion becomes intertwined with its spin state.

What is the Jahn-Teller effect?

Another key interaction comes from the lattice of ions in the crystal. Electrons interact with these ions and can locally distort the arrangement of surrounding nuclei. A specific form of this electron-lattice interaction is the Jahn-Teller effect, where the system lowers its energy by distorting the lattice and localizing the electrons. This leads to a coupling between the spin, orbital, and lattice degrees of freedom, resulting in entangled states.

How are they related and what is new in this study?

In this work, researchers demonstrate that electromagnetic waves can be used to detect these spin-orbit entangled states at specific resonance frequencies. This opens up a new way to study the dynamic coupling of these degrees of freedom in a broad range of strongly correlated materials. This approach provides insight into their rich phase diagrams, including charge and orbital order, complex magnetic phases, and metal-insulator transitions. It offers a path to explore the intricate interplay between spin, orbital, and lattice interactions, particularly in 3D correlated systems.

Spin-orbit states have their orbital part (texture and color) intertwined with the spins (arrows up/down).

When they are mixed (bottom), the spin-orbit mixing is detected at optical frequencies by polarized light. | Image by M. Àngels Vilella

This is a study led by ICMAB researchers in collaboration with researchers from the Universitat de Barcelona (UB) and the Universitat Rovira i Virgili (URV). The study has been published in Nature Communications.

Reference Article

Spin-orbit entanglement driven by the Jahn-Teller effect
Alejandro S. Miñarro, Mario Villa, Blai Casals, Florencio Sánchez, Jaume Gázquez & Gervasi Herranz.
Nat Commun 15, 8694 (2024)
doi.org/10.1038/s41467-024-52848-8

More information

Spin-orbit entanglement driven by the Jahn-Teller effect (Scientific Highlight at ICMAB website)

Jahn-Teller states mixed by spin-orbit coupling in an electromagnetic field (Scientific Highlight at ICMAB website)

Anna May

25 November 2024