Direct observation of the energy gain underpinning ferromagnetic superexchange in the electronic structure of CrGeTe$_3

• Main Authors: Watson, Matthew D, Marković, Igor, Mazzola, Federico, Rajan, Akhil, Morales, Edgar A, Burn, David M, Hesjedal, Thorsten, van der Laan, Gerrit, Mukherjee, Saumya, Kim, Timur K, Bigi, Chiara, Vobornik, Ivana, Hatnean, Monica Ciomaga, Balakrishnan, Geetha, King, Philip D. C
• Format: Journal Article
• Language: English
• Published: 24-12-2019
• Subjects: Physics - Materials Science; Physics - Strongly Correlated Electrons
• DOI: 10.48550/arxiv.1912.11314

Phys. Rev. B 101, 205125 (2020) We investigate the temperature-dependent electronic structure of the van der
Waals ferromagnet, CrGeTe$_3$. Using angle-resolved photoemission spectroscopy,
we identify atomic- and orbital-specific band shifts upon cooling through
${T_\mathrm{C}}$. From these, together with x-ray absorption spectroscopy and
x-ray magnetic circular dichroism measurements, we identify the states created
by a covalent bond between the Te ${5p}$ and the Cr ${e_g}$ orbitals as the
primary driver of the ferromagnetic ordering in this system, while it is the Cr
${t_{2g}}$ states that carry the majority of the spin moment. The ${t_{2g}}$
states furthermore exhibit a marked bandwidth increase and a remarkable
lifetime enhancement upon entering the ordered phase, pointing to a delicate
interplay between localized and itinerant states in this family of layered
ferromagnets.