1,409 research outputs found
Fundamentals on the Noncommutative Plane
We consider the addition of charged matter (``fundametals'') to
noncommutative Yang-Mills theory and noncommutative QED, derive Feynman rules
and tree-level potentials for them, and study the divergence structure of the
theory. These particles behave very much as they do in the commutative theory,
except that (1) they occupy bound-state wavefunctions which are essentially
those of charged particles in magnetic fields, and (2) there is slight momentum
nonconservation at vertices. There is no reduction in the degree of divergence
of charged fermion loops like that which affects nonplanar noncommutative
Yang-Mills diagrams.Comment: LaTeX, 25 pages, 8 figures; revised versio
Trends in ferromagnetism, hole localization, and acceptor level depth for Mn substitution in
We examine the intrinsic mechanism of ferromagnetism in dilute magnetic
semiconductors by analyzing the trends in the electronic structure as the host
is changed from GaN to GaP, GaAs and GaSb, keeping the transition metal
impurity fixed. In contrast with earlier interpretations which depended on the
host semiconductor, we found that a single mechanism is sufficient to explain
the ferromagnetic stabilization energy for the entire series.Comment: 4 figures; To appear in Appl. Phys. Let
First-principles investigation of the assumptions underlying Model-Hamiltonian approaches to ferromagnetism of 3d impurities in III-V semiconductors
We use first-principle calculations for transition metal impurities V, Cr,
Mn, Fe, Co and Ni in GaAs as well as Cr and Mn in GaN, GaP and GaSb to identify
the basic features of the electronic structure of these systems. The
microscopic details of the hole state such as the symmetry and the orbital
character, as well as the nature of the coupling between the hole and the
transition metal impurity are determined. This could help in the construction
of model Hamiltonians to obtain a description of various properties beyond what
current first-principle methods are capable of.Comment: 14 figure
Origin of room-temperature ferromagnetism in Mn doped semiconducting CdGeP2
CdGeP2 chalcopyrites doped with Mn have been recently found to exhibit room
temperature ferromagnetism. Isovalent substitution of the Cd site is expected,
however, to create antiferromagnetism, in analogy with the well-known CdTe:Mn
(d^5) case. However, chalcopyrite semiconductors exhibit low-energy intrinsic
defects. We show theoretically how ferromagnetism results from the interaction
of Mn with hole-producing intrinsic defects.Comment: 4 pages, 4 figures. (To appear in Phys. Rev. Lett.
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