475 research outputs found
Theory for superconductivity in (Tl,K)FeSe as a doped Mott insulator
Possible superconductivity in recently discovered (Tl,K)FeSe
compounds is studied from the viewpoint of doped Mott insulator. The Mott
insulating phase is examined to be preferred in the parent compound at
due to the presence of Fe vacancies. Partial filling of vacancies at the
Fe-sites introduces electron carriers and leads to electron doped
superconductivity. By using a two-orbital Hubbard model in the strong coupling
limit, we find that the s-wave pairing is more favorable at small Hund's
coupling, and d wave pairing is more favorable at large Hund's
coupling.Comment: 4+ pages, 3 figures, to appear in EP
Electrical and Chemical Analysis of the In-situ H2 Plasma Cleaned InGaSb-Al2O3 Interface
No abstract available
Classification of second harmonic generation effect in magnetic materials
The second harmonic generation (SHG) effect is a powerful tool for
characterizing the magnetic structures of materials. Bridging the connection
between the SHG effect and the symmetries of magnetic materials has been at the
frontier of fundamental research in condensed matter physics. The construction
of a complete and exclusive classification of SHG effect of magnetic materials
offers a straightforward approach to insight into these intriguing connections.
In this work, we proposed a comprehensive classification of the SHG effect in
magnetic materials using \emph{isomorphic group} method. Seven types of SHG
effect in magnetic materials have been classified by considering the symmetries
of the magnetic phases and the corresponding parent phases. This classification
clearly depicts the physical origins of the SHG effect in magnetic materials
with various symmetries. Specifically, the classification predicts that the
magnetism could also purely contribute to the even parts (not invariant under
time reversal operation, or -type) of the SHG effect, which enriches the
conventional understandings. In addition, a dictionary containing SHG and
linear magneto-optic effect of magnetic materials in MANGDATA database is
further established. The first-principles calculations on some representative
magnetic materials further validate the effectiveness of the proposed
classification. Our findings provide an efficient way to reveal the underlying
physics of the SHG effect in magnetic materials, and can help us to explore
magnetic properties via the SHG effect more conveniently and instructively
Multiparty Quantum Secret Report
A multiparty quantum secret report scheme is proposed with quantum
encryption. The boss Alice and her agents first share a sequence of
(+1)-particle Greenberger--Horne--Zeilinger (GHZ) states that only Alice
knows which state each (+1)-particle quantum system is in. Each agent
exploits a controlled-not (CNot) gate to encrypt the travelling particle by
using the particle in the GHZ state as the control qubit. The boss Alice
decrypts the travelling particle with a CNot gate after performing a
operation on her particle in the GHZ state or not. After the GHZ states (the
quantum key) are used up, the parties check whether there is a vicious
eavesdropper, say Eve, monitoring the quantum line, by picking out some samples
from the GHZ states shared and measure them with two measuring bases. After
confirming the security of the quantum key, they use the GHZ states remained
repeatedly for next round of quantum communication. This scheme has the
advantage of high intrinsic efficiency for qubits and the total efficiency.Comment: 4 pages, no figure
Efficient symmetric multiparty quantum state sharing of an arbitrary m-qubit state
We present a scheme for symmetric multiparty quantum state sharing of an
arbitrary -qubit state with Greenberger-Horne-Zeilinger states following
some ideas from the controlled teleportation [Phys. Rev. A \textbf{72}, 02338
(2005)]. The sender Alice performs Bell-state measurements on her
particles and the controllers need only to take some single-photon product
measurements on their photons independently, not Bell-state measurements, which
makes this scheme more convenient than the latter. Also it does not require the
parties to perform a controlled-NOT gate on the photons for reconstructing the
unknown -qubit state and it is an optimal one as its efficiency for qubits
approaches the maximal value.Comment: 6 pages, no figures; It simplifies the process for sharing an
arbitrary m-qubit state in Phys. Rev. A 72, 022338 (2005) (quant-ph/0501129
q-Form fields on p-branes
In this paper, we give one general method for localizing any form (q-form)
field on p-branes with one extra dimension, and apply it to some typical
p-brane models. It is found that, for the thin and thick Minkowski branes with
an infinite extra dimension, the zero mode of the q-form fields with q<(p-1)/2
can be localized on the branes. For the thick Minkowski p-branes with one
finite extra dimension, the localizable q-form fields are those with q<p/2, and
there are also some massive bound Kaluza-Klein modes for these q-form fields on
the branes. For the same q-form field, the number of the bound Kaluza-Klein
modes (but except the scalar field (q=0)) increases with the dimension of the
p-branes. Moreover, on the same p-brane, the q-form fields with higher q have
less number of massive bound KK modes. While for a family of pure geometrical
thick p-branes with a compact extra dimension, the q-form fields with q<p/2
always have a localized zero mode. For a special pure geometrical thick
p-brane, there also exist some massive bound KK modes of the q-form fields with
q<p/2, whose number increases with the dimension of the p-brane.Comment: 14 pages, 2 figures, published versio
New Family of Robust 2D Topological Insulators in van der Waals Heterostructures
We predict a new family of robust two-dimensional (2D) topological insulators
in van der Waals heterostructures comprising graphene and chalcogenides BiTeX
(X=Cl, Br and I). The layered structures of both constituent materials produce
a naturally smooth interface that is conducive to proximity induced new
topological states. First principles calculations reveal intrinsic
topologically nontrivial bulk energy gaps as large as 70-80 meV, which can be
further enhanced up to 120 meV by compression. The strong spin-orbit coupling
in BiTeX has a significant influence on the graphene Dirac states, resulting in
the topologically nontrivial band structure, which is confirmed by calculated
nontrivial Z2 index and an explicit demonstration of metallic edge states. Such
heterostructures offer an unique Dirac transport system that combines the 2D
Dirac states from graphene and 1D Dirac edge states from the topological
insulator, and it offers new ideas for innovative device designs
Quantum secure direct communication network with superdense coding and decoy photons
A quantum secure direct communication network scheme is proposed with quantum
superdense coding and decoy photons. The servers on a passive optical network
prepare and measure the quantum signal, i.e., a sequence of the -dimensional
Bell states. After confirming the security of the photons received from the
receiver, the sender codes his secret message on them directly. For preventing
a dishonest server from eavesdropping, some decoy photons prepared by measuring
one photon in the Bell states are used to replace some original photons. One of
the users on the network can communicate any other one. This scheme has the
advantage of high capacity, and it is more convenient than others as only a
sequence of photons is transmitted in quantum line.Comment: 6 pages, 2 figur
Spontaneous Mirror Parity Violation, Common Origin of Matter and Dark Matter, and the LHC Signatures
Existence of a mirror world in the universe is a fundamental way to restore
the observed parity violation in weak interactions and provides the lightest
mirror nucleon as a unique GeV-scale dark matter particle candidate. The
visible and mirror worlds share the same spacetime of the universe and are
connected by a unique space-inversion symmetry -- the mirror parity (P). We
conjecture that the mirror parity is respected by the fundamental interaction
Lagrangian, and study its spontaneous breaking from minimizing the Higgs vacuum
potential. The domain wall problem is resolved by a unique soft breaking
linear-term from the P-odd weak-singlet Higgs field. We also derive constraint
from the Big-Bang nucleosynthesis. We then analyze the neutrino seesaw for both
visible and mirror worlds, and demonstrate that the desired amounts of visible
matter and mirror dark matter in the universe arise from a common origin of CP
violation in the neutrino sector via leptogenesis. We derive the Higgs
mass-spectrum and Higgs couplings with gauge bosons and fermions. We show their
consistency with the direct Higgs searches and the indirect precision
constraints. We further study the distinctive signatures of the predicted
non-standard Higgs bosons at the LHC. Finally, we analyze the direct detections
of GeV-scale mirror dark matter by TEXONO and CDEX experiments.Comment: 55pp. PRD final version. Only minor refinements (including to comment
on the latest LHC Higgs searches in Sec.5 and estimate abundances of mirror
dark matter particles in Sec.6); more references adde
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