Wigner FK and BME researchers confirm the presence of ultralong spin lifetime in graphite, which is a big step towards the realization of spin computers

Moore’s law predicts (Moore 1965) that informatics devices should soon reach the limit where device speed can no longer be improved using conventional electronics. This has motivated the quest towards novel architectures, which include quantum computers, so-called neuromorphic computing (which essentially mimics the function of the human brain), and spintronics. The latter phrase is a merger of “spin” and the “electronics” associated “tronics” (S. A. Wolf et al. Science 16, 294 (2001).).

Spintronics is based on the concept of using the intrinsic angular momentum or spin of electrons as information carrier unit. The field has been active since the early 2000s and the 2007 Nobel Prize in Physics was awarded to Albert Fert and Peter Grünberg for spintronics-related research. Concurrent HDD head readers employ a spintronics based technology and random-access memories (RAM), based on such principles, have been produced in prototype form. Electron spins interact with the environment through relativistic interactions, thus their coherence is preserved much longer than their collective motion (the electric current). The major governing factor in spintronics is the spin-coherence time. Its length determines whether a material can be used for spintronics. In an international collaboration, Wigner RCP and BME researchers observed that the spin-relaxation time in graphite is an order of magnitude longer than that observed in any other materials.

Graphite is a common material, which has been known since ancient times. It is used for several purposes including writing, as a lubricant and polishing material, in material sciences, energy storage, and even in nuclear technologies. Interest in graphite was revitalized by the discovery of a single graphite layer, graphene, in 2004. The latter material has been proposed for spintronics purposes but its spin-relaxation lifetime was limited to a few nanoseconds and it had to be cooled to liquid helium temperatures (4 K) for its observation. The results reviewed herein showed a spin-relaxation lifetime in graphite around 100 ns at room temperature. Although it may not appear to be very long, it is still sufficient for spintronics applications.

The researchers of Wigner RCP, BME, École Polytechnique Fédérale de Lausanne (Switzerland), University of Notre Dame (USA), University of Regensburg, and Pavol Jozef Šafárik University (Slovakia) have shown that experiments in graphite have been misinterpreted in the past 80 years, and the theoretical description lacked the interpretation of a symmetry present in graphite, which results in ultralong relaxation lifetimes.

Publication:

Bence G. Márkus, Martin Gmitra, Balázs Dóra, Gábor Csősz, Titusz Fehér, Péter Szirmai, Bálint Náfrádi, Viktor Zólyomi, László Forró, Jaroslav Fabian, Ferenc Simon (2023). Ultralong 100 ns spin relaxation time in graphite at room temperature. Nature Communications. DOI: 10.1038/s41467-023-38288-w