Kapitza stabilization of a quantum critical order

We explore the mechanism to control the quantum order near a quantum critical point (QCP) using a fast drive by an external field. To illustrate the proposed approach, we consider the ferroelectric QCP, where the externally applied electric field couples to the incipient ferroelectric order parameter P in SrTiO₃ (STO). To estimate the magnitude of the effect and its dependence on the polarization of the field, we use the Ginzburg-Devonshire free-energy anharmonic parameters. We find that STO irradiated by continuous-wave, off-resonant, coherent light with suitable polarization can induce ferroelectric order. We also suggest the generation of a second harmonic signal and X-ray diffraction measurements of the resulting strain as the experimental signature of the stabilized order. The approach can be viewed as a field-theory extension of mechanical control of the Kapitza pendulum where fast base oscillations stabilize the inverted pendulum position and are an example of Kapitza state engineering [1]. We also draw similarities and differences between the Kapitza approach and Floquet engineering.

[1] Kuzmanovski, D., Aeppli, G., Rønnow, H. M., & Balatsky, A. V. (2022). Kapitza stabilization of a quantum critical order. arXiv preprint arXiv:2208.09491.