Coherent terahertz control of antiferromagnetic spin waves

Ultrafast charge and spin excitations in the elusive terahertz regime^{1, 2}of the electromagnetic spectrum play a pivotal role in condensed matter^{3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13.} The electric field of free-space terahertz pulses has provided a direct gateway to manipulating the motion of charges on the femtosecond timescale^{6, 7, 8, 9.} Here, we complement this process by showing that the magnetic component of intense terahertz transients enables ultrafast control of the spin degree of freedom. Single-cycle terahertz pulses switch on and off coherent spin waves in antiferromagnetic NiO at frequencies as high as 1 THz. An optical probe pulse with a duration of 8 fs follows the terahertz-induced magnetic dynamics directly in the time domain and verifies that the terahertz field addresses spins selectively by means of the Zeeman interaction. This concept provides a universal ultrafast means to control previously inaccessible magnetic excitations in the electronic ground state.

online published November 2010