Electrically controlled optical diode mechanism in a magnetoelectric crystal was discovered by the BME Complex Magnetic Structures research group. Published in Physical Review Letters.

The research group, leading an international collaboration, has studied the optical properties of a magnetoelectric antiferromagnet (Ba2CoGe2O7) in the terahertz frequency range. They found a optical diode effect, also known as non-reciprocal light absorption, meaning that a crystal absorbs the electromagnetic radiation for a given propagation direction but transmits most of the light for the counterpropagating radiation. The BME researchers could control the optical diode effect by electric fields. This study also revealed that tuning the electric field can switch the state of the antiferromagnetic domains of the sample, and this is the mechanism that allows for an electrical control of the optical diode effect. These results might enable the design of light switches in the terahertz domain based on antiferromagnets similar to Ba2CoGe2O7.

Our colleagues at the BME Department of Physics created a novel artificial molecule in nano-sized electronic circuits, at extremely low temperatures. In natural molecules, electrons can tunnel between neighboring atoms. In this new, artificial, so-called Andreev molecule, the artificial atoms are cca. 1000-times larger than natural atoms, and the tunneling of electrons happens via a superconducting electrode. Interestingly, the superconducting electrode can absorb and re-emit pairs of electrons from and to the molecule This is a feature absent in usual molecules, altering the energy spectrum which was now measured by the BME researchers for the first time. The artificial atoms of the Andreev molecule are created in semiconducting nanowires from the group of Prof. Jesper Nygard (University of Copenhagen). This newly demonstrated artificial molecule is an important step in the development of long-lived quantum bits. 

Press coverage of recent breakthrough experiments on Hungarian science portal qubit.hu. Featuring theoretical physicist and head of BME Institute of Physics, Gergely Zaránd.