Left-handed metamaterials matched to free space through mechanical tuning

We have proposed a unit cell with a hybridized electric-magnetic resonant mode. The electric and magnetic polarizabilities approximately match one each other in a certain frequency range around the resonance, so that the effective wave impedance matches the one of the free space. The left-handed behavior was demonstrated between 3.38 GHz and 3.59 GHz where the transmission coefficient approximately reaches 1 with negligible ripples. This fact can be interpreted as a very good impedance matching with the free space.