21 February 2013 Ultrafast terahertz spin dynamics: from phonon-induced spin order to coherent magnon control
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Ultrashort pulses in the terahertz (THz) spectral range allow us to study and control spin dynamics on time scales faster than a single oscillation cycle of light. In a first set of experiments, we harness an optically triggered coherent lattice vibration to induce a transient spin-density wave in BaFe2As2, the parent compound of pnictide superconductors. The time-dependent multi-THz response of the non-equilibrium phases shows that the ordering quasi-adiabatically follows a coherent lattice oscillation at a frequency as high as 5.5 THz. The results suggest important implications for unconventional superconductivity. In a second step, we utilize the magnetic field component of intense THz transients to directly switch on and off coherent spin waves in the antiferromagnetic nickel oxide NiO. A femtosecond optical probe traces the magnetic dynamics in the time domain and verifies that the THz field addresses spins selectively via Zeeman interaction. This concept provides a universal ultrafast handle on magnetic excitations in the electronic ground state.
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K. W. Kim, K. W. Kim, M. Porer, M. Porer, C. Bernhard, C. Bernhard, J. Demsar, J. Demsar, A. Pashkin, A. Pashkin, T. Kampfrath, T. Kampfrath, A. Sell, A. Sell, M. Wolf, M. Wolf, A. Leitenstorfer, A. Leitenstorfer, R. Huber, R. Huber, "Ultrafast terahertz spin dynamics: from phonon-induced spin order to coherent magnon control", Proc. SPIE 8623, Ultrafast Phenomena and Nanophotonics XVII, 862307 (21 February 2013); doi: 10.1117/12.2001236; https://doi.org/10.1117/12.2001236

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