Band Structure Near the Dirac Point in HgTe Quantum Wells with Critical Thickness.

Mercury telluride (HgTe) thin films with a critical thickness of 6.5 nm are predicted to possess a gapless Dirac-like band structure. We report a comprehensive study on gated and optically doped samples by magnetooptical spectroscopy in the THz range.

Topologically protected magnetoelectric switching in a multiferroic.

Electric control of magnetism and magnetic control of ferroelectricity can improve the energy efficiency of magnetic memory and data-processing devices. However, the necessary magnetoelectric switching is hard to achieve, and requires more than just a coupling between the spin and the charge degrees of freedom. Here we show that an application and subsequent removal of a magnetic field reverses the electric polarization of the multiferroic GdMnO, thus requiring two cycles to bring the system back to the original configuration.

Low loss and magnetic field-tunable superconducting terahertz metamaterial.

Superconducting terahertz (THz) metamaterial (MM) made from niobium (Nb) film has been investigated using a continuous-wave THz spectroscopy. The quality factors of the resonance modes at 0.132 THz and 0.