9,369 research outputs found
Focusing RKKY interaction by graphene P-N junction
The carrier-mediated RKKY interaction between local spins plays an important
role for the application of magnetically doped graphene in spintronics and
quantum computation. Previous studies largely concentrate on the influence of
electronic states of uniform systems on the RKKY interaction. Here we reveal a
very different way to manipulate the RKKY interaction by showing that the
anomalous focusing - a well-known electron optics phenomenon in graphene P-N
junctions - can be utilized to refocus the massless Dirac electrons emanating
from one local spin to the other local spin. This gives rise to rich spatial
interference patterns and symmetry-protected non-oscillatory RKKY interaction
with a strongly enhanced magnitude. It may provide a new way to engineer the
long-range spin-spin interaction in graphene.Comment: 9 pages, 4 figure
Thermal effect in hot QCD matter in strong magnetic fields
The quasiparticle model is improved by the free magnetic contribution to
investigated the QCD matter in a strong magnetic field. The
temperature-dependent bag function is determined by the thermodynamic
consistency to represent the difference in energy density between physical
vacuum and lowest state of QCD. It is found that the positive bag function
vanishes at high temperature indicating the deconfinement. The rapid decrease
of the bag function in stronger magnetic fields reveals the so-called inverse
magnetic catalysis. The interaction measure at high temperature remains so
large that the usual Stefan-Boltzmann limit can not be reached. We suggest a
limit for each landau level pressure. Finally, it is
demonstrated that the positive magnetization modified by the bag function and
free magnetic contribution indicates the paramagnetic characteristic of QCD
matter.Comment: 8 pages, 6 figures, accepted for publication in PR
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