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Using ultraviolet (UV) light, scientists have succeeded in switching an extremely conductive state on and off within seconds at the interface between two oxide materials. This newly discovered ‘light switch for electrons’ is a significant step towards light-controlled electronics and could also play a role in superconductivity one day. The findings have been published in Nature Materials. The international research team includes theoretical physicist Professor Rossitza Pentcheva (University of Duisburg-Essen) and her former colleague, Dr Benjamin Geisler (University of Florida).
‘The key aspect of our work is that an exceptionally conductive state can be switched on and off solely by light – almost like flipping a switch,’ says Professor Pentcheva from the Department of Physics at the University of Duisburg-Essen (UDE). ‘This opens up new possibilities to manipulate superconductivity in nickelates using ultrafast light pulses.’
At the centre of the investigation is NdNiO₂, a representative of the so-called infinite-layer nickelates. This class of materials is similar to copper oxide high-temperature superconductors and has gained increasing attention in recent years, as it becomes superconducting under specific conditions.
Already in 2020, Geisler and Pentcheva predicted that a so-called two-dimensional electron gas could form at the interface between the nickelate NdNiO₂ and the insulator strontium titanate (SrTiO₃) – an extremely thin layer in which electrons move almost without resistance. Such states are considered key to future developments in nanoelectronics, spintronics and quantum information. However, in previous experiments this electron gas did not appear, since the atoms at the interface mixed more strongly than expected – as shown in a collaborative study by Cornell, Stanford and Duisburg-Essen Universities published 2023 in Nature Materials.
The international research team now employed light as a targeted stimulus: in their experiments, they illuminated the interface with ultraviolet light while simultaneously measuring its electrical conductivity. In parallel, Geisler and Pentcheva carried out quantum-mechanical simulations on UDE’s supercomputer to precisely describe the behaviour of the electrons.
‘When the light is switched on, the material changes abruptly: its electrical resistance drops by up to a factor of a hundred thousand – the sample suddenly conducts around 100,000 times better,’ Pentcheva explains. The effect is caused by a tiny electric field at the interface, which channels the UV-induced electrons along an invisible track into an ultrathin layer. There, they move with remarkable ease and form a highly conductive electron gas. As soon as the light is switched off, the state disappears completely – the material returns to its original condition without any lasting change.
Prof. Dr Rossitza Pentcheva
University of Duisburg-Essen, Department of Physics, Theoretical Physics
Tel. +49 (0)203 379-2238
rossitza.pentcheva@uni-duisburg-essen.de
Sánchez-Manzano, D., Krieger, G., Raji, A. et al. Giant photoconductance at infinite-layer nickelate/SrTiO₃ interfaces via an optically induced high-mobility electron gas. Nature Materials (2025). https://doi.org/10.1038/s41563-025-02363-y
Light on – current on: UV radiation transforms the material’s interface into a highly conductive ele ...
Copyright: David Sánchez Manzano, AI-generated
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