When molecules are exposed to infrared light, they start to vibrate as they absorb energy. This well-known phenomenon inspired Andreas Hauser from the Institute of Experimental Physics at Graz University of Technology (TU Graz) to explore whether these vibrations could be used to create magnetic fields. As atomic nuclei are positively charged, movement of these charged particles results in the generation of magnetic fields. Focusing on metal phthalocyanines – ring-shaped, planar dye molecules – Hauser and his team have calculated that these molecules can indeed produce minute magnetic fields in the nanometre range when stimulated by infrared pulses. Their findings, which suggest that these fields can be accurately measured using nuclear magnetic resonance spectroscopy, have been published in the Journal of the American Chemical Society.

The Molecular Ballet

The team’s calculations relied on early laser spectroscopy research, coupled with cutting-edge electron structure theory and the use of supercomputers at the Vienna Scientific Cluster and TU Graz. When circularly polarised infrared light is directed at phthalocyanine molecules, it excites two perpendicular molecular vibrations simultaneously. This intricate dance of movement creates a small, localised magnetic field in the nanometre range, akin to a rumba couple twirling on the dance floor.

Molecules: The Building Blocks of Quantum Computers

By fine-tuning the infrared light, it is possible to manipulate the strength and direction of the magnetic field generated by the molecules. This transformative capability could transform the molecules into ultra-precise optical switches, potentially forming the basis for circuits in quantum computers.

From Theory to Practice: The Path Ahead

Hauser, alongside colleagues from the Institute of Solid State Physics at TU Graz and the University of Graz, is now gearing up to validate their findings experimentally. To do so, the phthalocyanine molecules must be strategically placed on a surface. However, this step alters the physical environment, impacting light-induced excitation and magnetic field characteristics. The team is actively seeking a support material that minimally interferes with the desired mechanism. Before diving into experiments, the physicists plan to computationally analyze the interactions between the deposited molecules, support material, and infrared light to identify the most promising configurations.