160 research outputs found
Tunable dynamical magnetoelectric effect in antiferromagnetic topological insulator MnBiTe films
More than forty years ago, axion was postulated as an elementary particle
with a low mass and weak interaction in particle physics to solve the strong
(charge conjugation and parity) puzzle. Axions are also
considered as a possible component of dark matter of the universe. However, the
existence of axions in nature has not been confirmed. Interestingly, axions
arise as pseudoscalar fields derived from the Chern-Simons theory in condensed
matter physics. In antiferromagnetic insulators, the axion field can become
dynamical induced by spin-wave excitations and exhibits rich exotic phenomena,
such as, the chiral magnetic effect, axionic polariton and so on. However, the
study of the dynamical axion field is rare due to the lack of real materials.
Recently, MnBiTe was discovered to be an antiferromagnetic topological
insulator with a quantized axion field protected by the inversion symmetry
and the magnetic-crystalline symmetry . Here, we
studied MnBiTe films in which both the and
symmetries are spontaneously broken and found that the dynamical axion field
and largely tunable dynamical magnetoelectric effects can be realized through
tuning the thickness of MnBiTe films, the temperature and the element
substitution. Our results open a broad avenue to study axion dynamics in
antiferromagnetic topological insulator MnBiTe and related materials,
and also is hopeful to promote the research of dark matter.Comment: 6 pages, 4 figure
A revised averaging method and general forms of approximate solution for nonlinear oscillator with only polynomial-type displacement nonlinearity
In this paper a revised averaging method is presented, that does not need the detuning factor in the solving procedure. Comparison with the traditional averaging method shows that it has the similar solving procedure and the same result as the primary resonance of the traditional averaging method. Then the nonlinear oscillator with only polynomial-type displacement nonlinearity is studied, and the general forms of the first-order approximate solution by this revised averaging method, and by the traditional averaging method for the super-harmonic resonance and sub-harmonic resonance are established. At last, the Duffing oscillator is investigated as an example, and the comparison of the analytical and numerical results proves the validity and simplicity of the presented method
Two-parameter estimation with three-mode NOON state in a symmetric three-well
We propose a theoretical scheme to realize two-parameter estimation via a
Bose-Einstein condensates confined in a symmetric triple-well. The three-mode
NOON state is prepared adiabatically as the initial state. Two phase
differences between the wells are two parameters to be estimated. With the help
of classical and quantum Fisher information, we study the sensitivity of the
triple-well on estimating two phase parameters simultaneously. The result shows
that the precision of simultaneous estimation of two parameters in a
triple-well system can reach the Heisenberg scaling
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