1,817 research outputs found
RKKY interaction in three-dimensional electron gases with linear spin-orbit coupling
We theoretically study the impacts of linear spin-orbit coupling (SOC) on the
Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities in two
kinds of three-dimensional noncentrosymmetric systems. It has been found that
linear SOCs lead to the Dzyaloshinskii-Moriya interaction and the Ising
interaction, in addition to the conventional Heisenberg interaction. These
interactions possess distinct range functions from three dimensional electron
gases and Dirac/Weyl semimetals. In the weak SOC limit, the Heisenberg
interaction dominates over the other two interactions in a moderately large
region of parameters. Sufficiently strong Rashba SOC makes the
Dzyaloshinskii-Moriya interaction or the Ising interaction dominate over the
Heisenberg interaction in some regions. The change in topology of the Fermi
surface leads to some quantitative changes in periods of oscillations of range
functions. The anisotropy of Ruderman-Kittel-Kasuya-Yosida interaction in
bismuth tellurohalides family BiTe ( = Br, Cl, and I) originates from
both the specific form of Rashba SOC and the anisotropic effective mass. Our
work provides some insights into understanding observed spin textures and the
application of these materials in spintronics.Comment: 11 pages, 4 figures, Final Version in PR
Stability studies of ZnO and AlN thin film acoustic wave devices in acid and alkali harsh environments
Surface acoustic wave (SAW) devices based on piezoelectric thin-films such as ZnO and AlN are widely used in sensing, microfluidics and lab-on-a-chip applications. However, for many of these applications, the SAW devices will inevitably be used in acid or alkali harsh environments, which may cause their early failures. In this work, we investigated the behavior and degradation mechanisms of thin film based SAW devices in acid and alkali harsh environments. Results show that under the acid and alkali attacks, chemical reaction and corrosion of ZnO devices are very fast (usually within 45 s). During the corrosion, the crystalline orientation of the ZnO film is not changed, but its grain defects are significantly increased and the grain sizes are decreased. The velocity of ZnO-based SAW devices is decreased due to the formation of porous structures induced by the chemical reactions. Whereas an AlN thin-film based SAW device does not perform well in acid–alkali conditions, it might be able to maintain a normal performance without obvious degradation for more than ten hours in acid or alkali solutions. This work could provide guidance for the applications of both ZnO or AlN-based SAW devices in acid/alkali harsh environments
Does the purchasing power parity fit for China?
This paper aims to assess whether the purchasing power parity (PPP) holds by examining the dynamic link between nominal exchange rate (NER) and relative consumer price (RCP) in China. With economic transitions and structural changes existing, we discover that by using full sample data the PPP does not hold. Consequently, we apply the rolling window causality method in order to reconsider the dynamic causal link, and as a result we observe NER having both positive and negative impacts on RCP in some sub-periods. However, RCP has no effect on the NER, meaning that the PPP does not hold. Trade cost, restrictions and imperfect competition are considered in explaining the deviations in some sub-sample periods. Therefore, this empirical result has important implications for stakeholders to distinguish factors that bring about the PPP deviations and further offers policy suggestions for the Chinese monetary authorit
- …