Light-induced states and non-equilibrium phases in antiferromagnets

• Applicants: Dr. Davide Bossini; Professor Dr. Johannes Knolle; Professor Dr. István Kézsmárki
• Subject Area: Experimental Condensed Matter Physics ; Theoretical Condensed Matter Physics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572654405

Exploring novel forms of antiferromagnetism and controlling their electronic and magnetic properties are trending in condensed-matter physics and materials science, partly fueled by the tremendous potential of these materials in next-generation information-processing and storage devices. Obvious advantages of antiferromagnets with respect to ferromagnets are their potentially faster operation, higher integrity, and enhanced stability against interfering magnetic fields. Although the latter makes the control of antiferromagnetic (AFM) states challenging, their appealing properties keep antiferromagnets in the focus of fundamental research and may also render them game changers in information technologies. Light has recently emerged as a highly promising tool to detect and manipulate AFM states, although its interaction with materials of zero net magnetization has been considered to be inherently weak. The PIs of the project have recently identified different types of antiferromagnets, where light-matter coupling is strong and demonstrated the optical imaging of antiferromagnetic domains in these systems. Built on this, our first objective is the ultrafast optical control of AFM states, namely the writing of antiferromagnetic domains by intense light pulses in magnetoelectric insulators and itinerant altermagnets. Despite the intense research activity, the understanding of how intense optical stimulus can bring antiferromagnets out of equilibrium, e.g., how femtosecond laser pulses can activate different magnetic phases, is still in its infancy. Our second objective aims at filling this gap by establishing efficient schemes for light-induced magnetic transitions in antiferromagnets, where the strong coupling of light to the AFM order was previously demonstrated by the PIs. The evolution of the system across the phase transition will be tracked in real time, thus disclosing that non-equilibrium states are directly triggered by the optical excitation. In addition to photo-induced transitions between conventional long-range ordered states, we seek to induce quantum spin liquid states by light in highly frustrated antiferromagnets. Our team contains 5 renowned groups, where the 3-3 PIs from the Japanese and the German side are all well-recognized researchers with complementarity expertise, also in advanced theoretical modelling. The proposed collaborative network comprises a large toolbox, including various linear and non-linear optical techniques, far beyond what is typically available in a single project. In our synergic approach, giving high priority to knowledge transfer among the partners, the combination of unique competences will grant the successful achievement of the ambitious goals.

• DFG Programme: Research Grants
• International Connection: Hungary, Japan
• Partner Organisation: Japan Society for the Promotion of Science (JSPS)
• Co-Investigator: Professor Francesco Piazza, Ph.D.
• Cooperation Partners: Professor Dr. Sándor Bordács; Professor Dr. Tsuyoshi Kimura; Dr. Naoki Ogawa; Professor Yoshinori Tokura