3,751 research outputs found
Hear the Sound of Weyl Fermions
Quasiparticles and collective modes are two fundamental aspects that
characterize a quantum matter in addition to its ground state features. For
example, the low energy physics for Fermi liquid phase in He-III was featured
not only by Fermionic quasiparticles near the chemical potential but also by
fruitful collective modes in the long-wave limit, including several different
sound waves that can propagate through it under different circumstances. On the
other hand, it is very difficult for sound waves to be carried by the electron
liquid in the ordinary metals, due to the fact that long-range Coulomb
interaction among electrons will generate plasmon gap for ordinary electron
density fluctuation and thus prohibits the propagation of sound waves through
it. In the present paper, we propose a unique type of acoustic collective modes
in Weyl semimetals under the magnetic field called chiral zero sound. The
chiral zero sound can be stabilized under so-called "chiral limit", where the
intra-valley scattering time is much shorter than the inter-valley one, and
only propagates along an external magnetic field for Weyl semimetals with
multiple-pairs of Weyl points. The sound velocity of the chiral zero sound is
proportional to the field strength in the weak field limit, whereas it
oscillates dramatically in the strong field limit, generating an entirely new
mechanism for quantum oscillations through the dynamics of neutral bosonic
excitation, which may manifest itself in the thermal conductivity measurements
under magnetic field.Comment: 9+16 pages, 2+0 figures, a new appendix added, accepted in PR
Light Induced Hall effect in semiconductors with spin-orbit coupling
We show that optically excited electrons by a circularly polarized light in a
semiconductor with spin-orbit coupling subject to a weak electric field will
carry a Hall current transverse to the electric field. This light induced Hall
effect is a result of quantum interference of the light and the electric field,
and can be viewed as a physical consequence of the spin current induced by the
electric field. The light induced Hall conductance is calculated for the p-type
GaAs bulk material, and the n-type and p-type quantum well structures.Comment: 5 pages, 3 figure
Metal-insulator transition in three-band Hubbard model with strong spin-orbit interaction
Recent investigations suggest that both spin-orbit coupling and electron
correlation play very crucial roles in the transition metal oxides. By
using the generalized Gutzwiller variational method and dynamical mean-field
theory with the hybridization expansion continuous time quantum Monte Carlo as
impurity solver, the three-band Hubbard model with full Hund's rule coupling
and spin-orbit interaction terms, which contains the essential physics of
partially filled sub-shell of materials, is studied
systematically. The calculated phase diagram of this model exhibits three
distinct phase regions, including metal, band insulator and Mott insulator
respectively. We find that the spin-orbit coupling term intends to greatly
enhance the tendency of the Mott insulator phase. Furthermore, the influence of
the electron-electron interaction on the effective strength of spin-orbit
coupling in the metallic phase is studied in detail. We conclude that the
electron correlation effect on the effective spin-orbit coupling is far beyond
the mean-field treatment even in the intermediate coupling region.Comment: 8 pages, 8 figure
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