13,964 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
Spin-dependent tunneling through a symmetric semiconductor barrier: the Dresselhaus effect
Spin-dependent tunneling through a symmetric semiconductor barrier is studied
including the k^3 Dresselhaus effect. The spin-dependent transmission of
electron can be obtained analytically. By comparing with previous work(Phys.
Rev. B 67. R201304 (2003) and Phys. Rev. Lett. 93. 056601 (2004)), it is shown
that the spin polarization and interface current are changed significantly by
including the off-diagonal elements in the current operator, and can be
enhanced considerably by the Dresselhaus effect in the contact regions.Comment: 10 pages, 5 figures, to appear in PR
Consistency check of charged hadron multiplicities and fragmentation functions in SIDIS
We derived the conditions on certain combinations of integrals of the
fragmentation functions of pion using HERMES data of the sum for the charged
pion multiplicities from semi-inclusive deep-inelastic scattering (SIDIS) off
the deuteron target. In our derivation the nucleon parton distribution
functions (PDFs) are assumed to be isospin SU(2) symmetric. Similar conditions
have also been obtained for the fragmentation functions (FFs) of kaon by the
sum of charged kaon multiplicities as well. We have chosen several FFs to study
the impact of those conditions we have derived. Among those FFs, only that
produced in the nonlocal chiral-quark model (NLQM) constantly satisfy the
conditions. Furthermore, the ratios of the strange PDFs and the
nonstrange PDFs extracted from the charged pion and kaon
multiplicities differ from each other significantly. Finally, we demonstrate
that the HERMES pion multiplicity data is unlikely to be compatible with the
two widely-used PDFs, namely CTEQ6M and NNPDF3.0.Comment: 11 pages, 5 fig
Artificial Gauge Field and Quantum Spin Hall States in a Conventional Two-dimensional Electron Gas
Based on the Born-Oppemheimer approximation, we divide total electron
Hamiltonian in a spinorbit coupled system into slow orbital motion and fast
interband transition process. We find that the fast motion induces a gauge
field on slow orbital motion, perpendicular to electron momentum, inducing a
topological phase. From this general designing principle, we present a theory
for generating artificial gauge field and topological phase in a conventional
two-dimensional electron gas embedded in parabolically graded
GaAs/InGaAs/GaAs quantum wells with antidot lattices. By tuning
the etching depth and period of antidot lattices, the band folding caused by
superimposed potential leads to formation of minibands and band inversions
between the neighboring subbands. The intersubband spin-orbit interaction opens
considerably large nontrivial minigaps and leads to many pairs of helical edge
states in these gaps.Comment: 9 pages and 4 figure
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