2,687 research outputs found
Unconventional thermoelectric behaviors and enhancement of figure of merit in Rashba spintronic systems
Thermoelectric transport in strongly spin-orbit coupled two-dimensional
Rashba system is studied using the exact solution of the linearized Boltzmann
equation. Some unusual transport behaviors are revealed. We show that the
electrical conductivity takes a Drude form when the Fermi energy is
above the band crossing point, but a non-Drude form which is a quadratic
function of when lies below the band crossing point. The Mott
relation breaks down when lies in the vicinity of the band crossing
point. It is shown that the thermopower and thermoelectric figure of merit are
strongly enhanced when downs below the band crossing point. This
enhancement is attributed to not only the one-dimensional-like density of state
but also the unconventional intraband elastic scattering below the band
crossing point. The differences between these results and those obtained by the
relaxation time approximation are discussed in detail.Comment: 9 pages, 5 figure
Thermoelectric response of spin polarization in Rashba spintronic systems
Motivated by recent discovery of strongly spin-orbit coupled two-dimensional
(2D) electron gas near the surface of Rashba semiconductors BiTeX (X=Cl, Br,
I), we calculate thermoelectric responses of spin polarization in 2D Rashba
model using an exact solution of the linearized Boltzmann equation for elastic
scattering. When the Fermi energy lies below the band crossing point we
find a non-Edelstein electric-field induced spin polarization which is linear
in . We show that the Mott-like relation between spin polarizations
induced by the temperature gradient and electric field breaks down
significantly when lies in the vicinity of the band crossing point. As
the temperature tends to zero, the temperature-gradient induced spin
polarization vanishes. These results differ from previous ones obtained by
relaxation time approximations.Comment: 9 pages, 3 figure
Scaling Law for Time-Reversal-Odd Nonlinear Transport
Time-reversal-odd (-odd) nonlinear current response has been
theoretically proposed and experimentally confirmed recently. However, the role
of disorder scattering in the response, especially whether it contributes to
the -independent term, has not been clarified. In this work, we
derive a general scaling law for this effect, which accounts for multiple
scattering sources. We show that the nonlinear conductivity is generally a
quartic function in . Besides intrinsic contribution, extrinsic
contributions from scattering also enter the zeroth order term, and their
values can be comparable to or even larger than the intrinsic one. Terms beyond
zeroth order are all extrinsic. Cubic and quartic terms must involve skew
scattering and they signal competition between at least two scattering sources.
The behavior of zeroth order extrinsic terms is explicitly demonstrated in a
Dirac model. Our finding reveals the significant role of disorder scattering in
-odd nonlinear transport, and establishes a foundation for
analyzing experimental result.Comment: 5 pages, 1 figur
Uncertainty-Aware Bootstrap Learning for Joint Extraction on Distantly-Supervised Data
Jointly extracting entity pairs and their relations is challenging when
working on distantly-supervised data with ambiguous or noisy labels. To
mitigate such impact, we propose uncertainty-aware bootstrap learning, which is
motivated by the intuition that the higher uncertainty of an instance, the more
likely the model confidence is inconsistent with the ground truths.
Specifically, we first explore instance-level data uncertainty to create an
initial high-confident examples. Such subset serves as filtering noisy
instances and facilitating the model to converge fast at the early stage.
During bootstrap learning, we propose self-ensembling as a regularizer to
alleviate inter-model uncertainty produced by noisy labels. We further define
probability variance of joint tagging probabilities to estimate inner-model
parametric uncertainty, which is used to select and build up new reliable
training instances for the next iteration. Experimental results on two large
datasets reveal that our approach outperforms existing strong baselines and
related methods.Comment: ACL 2023 main conference short pape
Synthesis and structure of the inclusion complex {NdQ[5]K@Q[10](H₂O)4}·4NO₃·20H₂O
Heating a mixture of Nd(NO₃)₃·6H₂O, KCl, Q[10] and Q[5] in HCl for 10 min affords the inclusion complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O. The structure of the inclusion complex has been investigated by single crystal X-ray diffraction and by X-ray Photoelectron spectroscopy (XPS)
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