Driving Multiferroicity in BaFe₁₂O₁₉Using Tunable THz Pulses, Part II: Symmetry Dynamics

Resonant excitation of individual vibrational modes presents a promising approach to non-equilibrium materials engineering. Recent work has shown that leveraging nonlinear couplings between phonons can overcome the quantum fluctuations that destabilize ferroelectric order in quantum paraelectrics. In the second part of this two-part talk, I will discuss the results of our technique employing narrow-bandwidth mid-infrared (MIR) light to selectively drive specific phonon activity in M-type barium hexaferrite (BaM). Through time-resolved second harmonic generation, we observe that resonantly pumping modes strongly coupled to strain alters the crystalline symmetry and induces a transient polar order at room temperature. These findings suggests that terahertz light can manipulate strain to not only overcome the quantum fluctuations at low temperature but to access proximal hidden ferroic phases at room temperature.