Thu, 13.01.2022  |  16:00 - 17:00
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Ultrafast optical manipulation and probing of antiferromagnetic states

Dr. Christian Tzschaschel | Harvard University, Dept. of Chemistry and Chemical Biology

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Antiferromagnets are a promising class of materials with the potential to enable the next generation of energy-efficient spintronic device concepts. In particular, the high frequency of antiferromagnetic (AFM) spin resonances – often in the THz regime – suggests the possibility to coherently control AFM order on sub-picosecond time scales thus outpacing established ferromagnetic information technologies. Controlling AFM states, however, is often challenging due to their insensitivity to external fields. Finding new mechanisms for manipulating and probing antiferromagnetic states is therefore a crucial prerequisite for realizing breakthrough antiferromagnetic spintronics. ere, I show how ultrafast near-infrared laser pulses can trigger coherent spin precessions in fully compensated antiferromagnets. These spin precessions result in a symmetry reduction of the AFM order. I present time-resolved optical second-harmonic generation as a symmetry sensitive technique that enables us to track the motion of the AFM order parameter and even allows separating electron from spin dynamics in a single measurement. Beyond classical antiferromagnets, I will further discuss how electron topology enables fundamentally new pathways for manipulating and probing AFM states. These recent results open up for the ultrafast investigation of the interplay between topology and magnetism in the emerging class of topological quantum magnets.