6,033 research outputs found
Spin Hall effect and Berry phase in two dimensional electron gas
The spin Hall effect is investigated in a high mobility two dimensional
electron system with the spin-orbital coupling of both the Rashba and the
Dresselhaus types. A spin current perpendicular to the electric field is
generated by either the Rashba or the Dresselhaus coupling. The spin Hall
conductance is independent of the stength of the coupling, but its sign is
determined by the relative ratio of the two couplings. The direction of spin
current is controllable by tuning the magnitude of the surface electric field
perpendicular to the two dimensional plane via adjusting the Rashba coupling.
It is observed that the spin Hall conductance has a close relation to the Berry
phase of conduction electrons.Comment: 4 paper, 1 figure
Childhood Health Status and Adulthood Cardiovascular Disease Morbidity in Rural China: Are They Related?
Cardiovascular diseases (CVDs) are among the top health problems of the Chinese population. Although mounting evidence suggests that early childhood health status has an enduring effect on late life chronic morbidity, no study so far has analyzed the issue in China. Using nationally representative data from the 2013 China Health and Retirement Longitudinal Study (CHARLS), a Probit model and Two-Stage Residual Inclusion estimation estimator were applied to analyze the relationship between childhood health status and adulthood cardiovascular disease in rural China. Good childhood health was associated with reduced risk of adult CVDs. Given the long-term effects of childhood health on adulthood health later on, health policy and programs to improve the health status and well-being of Chinese populations over the entire life cycle, especially in persons’ early life, are expected to be effective and successful
Spin transverse force and quantum transverse transport
We present a brief review on spin transverse force, which exerts on the spin
as the electron is moving in an electric field. This force, analogue to the
Lorentz force on electron charge, is perpendicular to the electric field and
spin current carried by the electron. The force stems from the spin-orbit
coupling of electrons as a relativistic quantum effect, and could be used to
understand the Zitterbewegung of electron wave packet and the quantum
transverse transport of electron in a heuristic way.Comment: 4 pages, manuscript of invited talk on IAS Workshop on Spintronics at
Nanyang Techological University, Singapore, 200
Topological superconducting states in monolayer FeSe/SrTiO
The monolayer FeSe with a thickness of one unit cell grown on a
single-crystal SrTiO substrate (FeSe/STO) exhibits striking
high-temperature superconductivity with transition temperature over 65K
reported by recent experimental measurements. In this work, through analyzing
the distinctive electronic structure, and providing systematic classification
of the pairing symmetry , we find that both -and -wave pairing with odd
parity give rise to topological superconducting states in monolayer FeSe, and
the exotic properties of -wave topological superconducting states have close
relations with the unique non-symmorphic lattice structure which induces the
orbital-momentum locking. Our results indicate that the monolayer FeSe could be
in the topological nontrivial -wave superconducting states if the relevant
effective pairing interactions are dominant in comparison with other
candidates.Comment: 11 pages, 4 figure
Topological phase in one-dimensional interacting fermion system
We study a one-dimensional interacting topological model by means of exact
diagonalization method. The topological properties are firstly examined with
the existence of the edge states at half-filling. We find that the topological
phases are not only robust to small repulsive interactions but also are
stabilized by small attractive interactions, and also finite repulsive
interaction can drive a topological non-trivial phase into a trivial one while
the attractive interaction can drive a trivial phase into a non-trivial one.
Next we calculate the Berry phase and parity of the bulk system and find that
they are equivalent in characterizing the topological phases. With them we
obtain the critical interaction strengths and construct part of the phase
diagram in the parameters space. Finally we discuss the effective Hamiltonian
at large-U limit and provide additional understanding of the numerical results.
Our these results could be realized experimentally using cold atoms trapped in
the 1D optical lattice.Comment: 7 pages, 5 figures; revised version, references added, Accepted for
publication in Physical Review
Quantum Anomalous Hall Effect in Flat Band Ferromagnet
We proposed a theory of quantum anomalous Hall effect in a flat-band
ferromagnet on a two-dimensional (2D) decorated lattice with spin-orbit
coupling. Free electrons on the lattice have dispersionless flat bands, and the
ground state is highly degenerate when each lattice site is occupied averagely
by one electron, i.e., the system is at half filling. The on-site Coulomb
interaction can remove the degeneracy and give rise to the ferrimagnetism,
which is the coexistence of the ferromagnetic and antiferromagnetic long-range
orders. On the other hand the spin-orbit coupling makes the band structure
topologically non-trivial, and produces the quantum spin Hall effect with a
pair of helical edge states around the system boundary. Based on the rigorous
results for the Hubbard model, we found that the Coulomb interaction can
provide an effective staggered potential and turn the quantum spin Hall phase
into a quantum anomalous Hall phase
Finite-temperature conductivity and magnetoconductivity of topological insulators
The electronic transport experiments on topological insulators exhibit a
dilemma. A negative cusp in magnetoconductivity is widely believed as a quantum
transport signature of the topological surface states, which are immune from
localization and exhibit the weak antilocalization. However, the measured
conductivity drops logarithmically when lowering temperature, showing a typical
feature of the weak localization as in ordinary disordered metals. Here, we
present a conductivity formula for massless and massive Dirac fermions as a
function of magnetic field and temperature, by taking into account the
electron-electron interaction and quantum interference simultaneously. The
formula reconciles the dilemma by explicitly clarifying that the temperature
dependence of the conductivity is dominated by the interaction while the
magnetoconductivity is mainly contributed by the quantum interference. The
theory paves the road to quantitatively study the transport in topological
insulators and other two-dimensional Dirac-like systems, such as graphene,
transition metal dichalcogenides, and silicene.Comment: 5 pages, 5 figure
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