Towards coupling coherent femtosecond charge and spin dynamics in antiferromagnets

Davide Bossini, University of Konstanz

The pressing demand to develop novel information technology schemes has bolstered the research area of spintronics. In particular, the colossal amount of data to process and transfer, especially in the cloud, have pushed researchers to explore concepts for an ever faster and less energy-demanding method to record and handle information. A possible approach consists in employing femtosecond laser pulses to optically generate spin dynamics in magnetic materials. One of the possible outcomes of the light-spin interaction on the sub-picosecond time-scale is the generation of coherent magnons. This process has been demonstrated [1-2] even in the absence of absorption of light by the lattice [3]. Additionally both low- and high-energy magnons can be induced and coherently manipulated [4-5]. In my talk I will introduce first some aspects of the all-optical generation of coherent magnons on the ultrashort time-scale, discussing several possible mechanisms. Furthermore I will focus on the possibility to drive an hybrid electronic-magnonic transition, called exciton-magnon, which allows to arbitrarily amplify coherent THz spin oscillations. In addition, exploring this concept in a multi-domain antiferromagnet, an unprecedented coupling between diﬀerent magnon modes was reported, as the ultrafast spin dynamics enters the nonlinear regime. This eﬀect was proved both experimentally and theoretically to be due to the domain walls, which are eﬀectively able to couple diﬀerent magnon modes in diﬀerent domains [6-7]. While this discovery enables perspectives of coherent transfer of energy on the picosecond time- and (sub)-micrometer length-scale, the implications for the electronic system are left open to investigate.

[1] Nature 435, 655 (2005)
[2] Physical Review Letters 105, 077402 (2010)
[3] Physical Review B 89, 060405(R) (2014)
[4] Nature Communications 7, 10645 (2016)
[5] Physical Review B 100, 024428 (2019)
[6] J. Phys. D: Appl. Phys. 54, 374004 (2021)
[7] Physical Review Letters 127, 077202 (2021)

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PDF file of the talk available here