In a recent ACS Nano publication (featured on a cover), an international research team has revealed how assemblies of radical organic molecules on a superconducting surface can host different quantum states. By precisely placing these molecules and probing them with scanning tunneling microscopy (STM), the researchers observed distinct resonances within the superconducting gap known as Yu–Shiba–Rusinov states—electronic excitations that arise when local magnetic moments interact with superconducting electrons.
The data show that varying the distance and orientation of molecules alters their magnetic coupling, driving transitions between singlet and doublet ground states. This is significant because it offers a strategy to control and engineer the quantum behavior of molecular assemblies—an essential step toward quantum electronics or spintronics applications. For example, the work shows that a tetramer ensemble can be switched between two distinct charge configurations nondestructively using just the probing tip. Tetramer can therefore serve as an information unit.
The theoretical explanation of the experiments was provided by Dr. Martin Žonda of our theoretical group and Dr. Vladislav Pokorný from the Institute of Physics of the Czech Academy of Sciences. By combining advanced numerical methods with physical insights, they successfully predicted conditions under which the system changes its state and how the Yu–Shiba–Rusinov peaks shift in the spectra.
The findings presented in the paper pave the way for designing “tailored” quantum materials, in which magnetic molecules are precisely arranged on superconductors to achieve targeted properties. Beyond fundamental research, this progress could eventually inform the development of novel nanoelectronic devices or superconducting logic elements.
For more information, see the full article in ACS Nano or contact our theory group.
