Large-Amplitude Spin Dynamics Driven by a THz Pulse in Resonance with an Electromagnon

Abstract

Multiferroics have attracted strong interest for potential applications where electric fields control magnetic order. The ultimate speed of control via magnetoelectric coupling, however, remains largely unexplored. Here, we report an experiment in which we drove spin dynamics in multiferroic TbMnO3 with an intense few-cycle terahertz (THz) light pulse tuned to resonance with an electromagnon, an electric-dipole active spin excitation. We observed the resulting spin motion using time-resolved resonant soft x-ray diffraction. Our results show that it is possible to directly manipulate atomic-scale magnetic structures with the electric field of light on a sub-picosecond time scale.

Terahertz Sum-Frequency Excitation of a Raman-Active Phonon

“…Many control strategies take advantage of terahertz (THz) modes of the material. An ubiquitous example is lattice vibrations (phonons) whose control by femtosecond laser pulses [4,5] has enabled new pathways to permanent material modification [6], insulator-to-metal transitions [7,8], and magnetization manipulation [2,9].…”

“…Gaining control over ultrafast elementary motions of electrons, spins, and ions in solids is of major scientific and applied interest. Examples include steering of chemical reactions along a desired pathway [1] and switching of spins in magnetically ordered materials [2,3]. Many control strategies take advantage of terahertz (THz) modes of the material.…”

Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

“…Recently, the advance of intense THz sources towards E0.1 GV m À 1 field strength enabled first observations of nonlinear light matter interactions [2][3][4][5][6] , the induction of insulator-to-metal transitions 7 and the cause of DNA damage 8 . However, a large range of THz applications, ranging from ultrafast domain switching [9][10][11] to particle acceleration 12 , requires a giant leap in brightness to match the theoretically predicted needs in field strength being on the order of a few GV m À 1 .…”

Combining THz laser excitation with resonant soft X-ray scattering at the Linac Coherent Light Source

“…This motivates the use of lower-energy laser sources because resonant pumping can be performed to separate these mechanisms. By tuning to different types of modes, the physics in complex systems can be unraveled on ultrafast timescales such as in the recent study of electromagnons (Kubacka et al, 2014).…”

“…Recent work has even utilized pulsed pumping schemes at specialized photon energies to exclusively excite phonons (Fö rst et al, 2011(Fö rst et al, , 2013 as a route to material control. However, using low-photon-energy excitation to study the intricate workings of quantum materials (Kubacka et al, 2014) is an area which has so far been under-utilized, but remains quite promising.…”