Fysiker publicerade i tidskriften Physical Review Letters
Ska även presentera artikeln vid American Physical Societys årliga sammankomst i Dallas i mars.
Carlo Canali, professor i fysik vid Linnéuniversitetet, och Tor Olof Strandberg, tidigare doktorand vid universitetet, har tillsammans med professor Allan H MacDonald vid University of Texas at Austin fått en artikel publicerad i januari månads utgåva av Physical Review Letters (Vol.106, No.1). Artikeln bär titeln ”Chern number spins of Mn acceptor magnets in GaAs” och finns att läsa online på http://link.aps.org/doi/10.1103/PhysRevLett.106.017202.
Utifrån detta arbete har Carlo Canali även blivit inbjuden att tala vid American Physical Societys årliga konferens i Dallas den 21-25 mars. Läs mer på www.aps.org/meetings/march/index.cfm.
Former Ph.D. student Tor Olof Strandberg and Professor Carlo M. Canali of Linnaeus University, together with Professor Allan H. MacDonald at the University of Texas at Austin have recently published a paper in Physical Review Letters, entitled ”Chern number spins of Mn acceptor magnets in GaAs”.
The paper presents a theoretical study of the properties of magnetic impurities in semiconductors. This is a topic of present great interest in condensed matter physics, for its relevance to nanospintronics and quantum information processing. This work is in part motivated by ongoing STM experiments carried out by some of the leading experimental groups in the field.
In the paper the authors argue that small clusters of Mn impurities in GaAs represent novel magnetic entities for which they coined the name acceptor or donor magnets. Under certain conditions, the magnetic behaviour of these composite objects can be described by a one effective quantum spin that includes the local moments of the impurities and the spin and orbital moments of the itinerant acceptor states associated to them. This total spin can be identified with a topological quantity known as Berry phase Chern number. As an example of the theory, the authors have carried out calculations for one and two Mn atoms in GaAs. The calculations show the value of the total spin for one Mn atom in GaAs changes from the known value J = 1 for the Mn in bulk to J = 2 when the Mn is inserted in one of the layers close to the surface, due to quenching of the acceptor orbital moment. For two Mn atoms, the theory predicts a more complex dependence of the total spin on pair direction and Mn atom separation. Berry phase corrections included in the theory influence qualitatively the quantum spin dynamics of these acceptor magnets.
These predictions are in principle testable in the STM experiments that are currently being carried out around the world.
Professor Canali has been invited to present a talk on this topic at the March Meeting of the American Physical Society, which will take place in Dallas on March 21-25, 2011. www.aps.org/meetings/march/index.cfm