Tunable terahertz metamaterials with negative permeability

We demonstrate experimentally and theoretically dielectric metamaterials exhibiting a tunable range of negative effective permeability in the terahertz spectral region (0.2--0.36 THz). Our structures consist of an array of intrinsically nonmagnetic rods made of an incipient ferroelectric ${\text{SrTiO}}_{3}$ which shows a high tunable permittivity. The magnetic response and its tuning are achieved by a temperature control of the permittivity of ${\text{SrTiO}}_{3}$, which defines the resonant confinement of the electromagnetic field within the rods.