18,984 research outputs found
Dynamical correlation functions and the related physical effects in three-dimensional Weyl/Dirac semimetals
We present a unified derivation of the dynamical correlation functions
including density-density, density-current and current-current, of
three-dimensional Weyl/Dirac semimetals by use of the Passarino-Veltman
reduction scheme at zero temperature. The generalized Kramers-Kronig relations
with arbitrary order of subtraction are established to verify these correlation
functions. Our results lead to the exact chiral magnetic conductivity and
directly recover the previous ones in several limits. We also investigate the
magnetic susceptibilities, the orbital magnetization and briefly discuss the
impact of electron interactions on these physical quantities within the random
phase approximation. Our work could provide a starting point for the
investigation of the nonlocal transport and optical properties due to the
higher-order spatial dispersion in three-dimensional Weyl/Dirac semimetals.Comment: 21 pages, 3+1 figures, 1 table. Accepted in PR
Anomalous spin Hall effects in Dresselhaus (110) quantum wells
Anomalous spin Hall effects that belong to the intrinsic type in Dresselhaus
(110) quantum wells are discussed. For the out-of-plane spin component,
antisymmetric current-induced spin polarization induces opposite spin Hall
accumulation, even though there is no spin-orbit force due to Dresselhaus (110)
coupling. A surprising feature of this spin Hall induction is that the spin
accumulation sign does not change upon bias reversal. Contribution to the spin
Hall accumulation from the spin Hall induction and the spin deviation due to
intrinsic spin-orbit force as well as extrinsic spin scattering, can be
straightforwardly distinguished simply by reversing the bias. For the inplane
component, inclusion of a weak Rashba coupling leads to a new type of
intrinsic spin Hall effect solely due to spin-orbit-force-driven spin
separation.Comment: 6 pages, 5 figure
Switching off the magnetic exchange coupling by quantum resonances
We clarify the role of quantum-well states in magnetic trilayer systems from
majority carrier in the ferromagnetic and all carriers in the antiferromagnetic
configurations. In addition to numerical and analytic calculations, heuristic
pictures are provided to explain effects of a capping layer and side-layer
modulation in recent experiments. This immediately offers answers to two
unexplained subtle findings in experiments and band-structure calculations,
individually. Furthermore, it allows a more flexible tuning of or even turning
off the interlayer exchange coupling.Comment: 5 pages, 5 figure
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