Light pulses enable next-generation stable data storage
Traditional data storage systems rely on ferroic materials, such as ferromagnets or ferroelectrics, which can flip between two stable states under external magnetic or electric fields. However, these systems are prone to interference and degradation, driving efforts to find more stable alternatives.
Ferroaxial materials, a newly identified member of the ferroic family, exhibit vortices of electric dipoles that can rotate in two opposing directions without generating an overall magnetic or electric polarization. This inherent stability has made them attractive for data storage - but their resistance to external manipulation has limited practical use.
The research team led by Andrea Cavalleri overcame this challenge by using circularly polarized terahertz pulses to toggle ferroaxial domains in rubidium iron dimolybdate (RbFe(MoO4)2). "We take advantage of a synthetic effective field that arises when a terahertz pulse drives ions in the crystal lattice in circles," explained lead author Zhiyang Zeng. "This effective field is able to couple to the ferroaxial state, just like a magnetic field would switch a ferromagnet or an electric field would reverse a ferroelectric state."
"By adjusting the helicity, or twist, of the circularly polarized light pulses, we can selectively stabilize a clockwise or anti-clockwise rotational arrangement of the electric dipoles," added co-author Michael Forst. "In this way enabling information storage in the two ferroic states. Because ferroaxials are free from depolarizing electric or stray magnetic fields, they are extremely promising candidates for stable, non-volatile data storage."
"This is an exciting discovery that opens up new possibilities for the development of a robust platform for ultrafast information storage," said Cavalleri. "It also shows how circular phonon fields, first achieved in our group in 2017, are emerging as a new resource for the control of exotic material phases."
The research was supported by the Max Planck Society and the Max-Planck Graduate Center for Quantum Materials, with collaborations involving the University of Oxford. The MPSD also receives funding from the Deutsche Forschungsgemeinschaft through the Cluster of Excellence "CUI: Advanced Imaging of Matter" and partners with the Center for Free-Electron Laser Science (CFEL), DESY, and the University of Hamburg.
Research Report:Photo-induced nonvolatile rewritable ferroaxial switching
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