November 28, 2022

A new candidate material for Quantum Spin Liquids

Scientists at EPFL’s School of Basic Sciences have successfully produced and studied a Quantum Spin Liquid (QSL) in a highly original material known as EDT-BCO. The system was designed and synthesized at Université d’Angers, France (CNRS).

In 1973, physicist and later Nobel laureate Philip W. Anderson proposed a bizarre state of matter: the Quantum Spin Liquid (QSL). Unlike the everyday liquids we know, the QSL actually has to do with magnetism – and magnetism has to do with spin.

What is exciting about QSLs is that they can be used in a number of applications. Because they come in different varieties with different properties, QSLs can be used in quantum computing, telecommunications, superconductors, spintronics (a variation of electronics that uses electron spin instead of current), and a host of other quantum-based technologies.

But before exploiting them, we first have to gain a solid understanding of QSL states. To do this, scientists have to find ways to produce QSLs on demand – a task that has proven difficult so far, with only a few materials on offer as QSL candidates.

The structure of EDT-BCO is what makes it possible to create a QSL. The electron spins in the EDT-BCO form triangularly organized dimers, each of which has a spin-1/2 magnetic moment which means that the electron must fully rotate twice to return to its initial configuration. The layers of spin-1/2 dimers are separated by a sublattice of carboxylate anions centred by a chiral bicyclooctane. The anions are called “rotors” because they have conformational and rotational degrees of freedom.

The unique rotor component in a magnetic system makes the material special amongst QSL candidates, representing a new material family.

The scientists and their collaborators employed an arsenal of methods to explore the EDT-BCO as a QSL material candidate: density functional theory calculations, high-frequency electron spin resonance measurements, nuclear magnetic resonance, and muon spin spectroscopy. All of these techniques explore the magnetic properties of EDT-BCO from different angles.

The work has significant implications for future technologies, from quantum computing to superconductivity and spintronics.

The work has been published in PNAS.

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