2,348 research outputs found
Topological Quantum Phase Transition in 5 Transition Metal Oxide NaIrO
We predict a quantum phase transition from normal to topological insulators
in the 5 transition metal oxide NaIrO, where the transition can be
driven by the change of the long-range hopping and trigonal crystal field
terms. From the first-principles-derived tight-binding Hamiltonian we determine
the phase boundary through the parity analysis. In addition, our
first-principles calculations for NaIrO model structures show that the
interlayer distance can be an important parameter for the existence of a
three-dimensional strong topological insulator phase. NaIrO is
suggested to be a candidate material which can have both a nontrivial topology
of bands and strong electron correlations
ULTRASONOGRAPHY: changes in submission and publication patterns 1 year after being listed in SCIE
11Nsciescopu
Hepatic Cavernous Hemangioma in Cirrhotic Liver: Imaging Findings
Objective: To document the imaging findings of hepatic cavernous hemangioma
detected in cirrhotic liver.
Materials and Methods: The imaging findings of 14 hepatic cavernous hemangiomas
in ten patients with liver cirrhosis were retrospectively analyzed. A diagnosis
of hepatic cavernous hemangioma was based on the findings of two or
more of the following imaging studies: MR, including contrast-enhanced dynamic
imaging (n = 10), dynamic CT (n = 4), hepatic arteriography (n = 9), and US (n =
10).
Results: The mean size of the 14 hepatic hemangiomas was 0.9 (range, 0.5
1.5) cm in the longest dimension. In 11 of these (79%), contrast-enhanced
dynamic CT and MR imaging showed rapid contrast enhancement of the entire
lesion during the early phase, and hepatic arteriography revealed globular
enhancement and rapid filling-in. On contrast-enhanced MR images, three
lesions (21%) showed partial enhancement until the 5-min delayed phases. US
indicated that while three slowly enhancing lesions were homogeneously hyperechoic,
9 (82%) of 11 showing rapid enhancement were not delineated.
Conclusion: The majority of hepatic cavernous hemangiomas detected in cirrhotic
liver are small in size, and in many, hepatic arteriography and/or contrastenhanced
dynamic CT and MR imaging demonstrates rapid enhancement. US,
however, fails to distinguish a lesion of this kind from its cirrhotic background.ope
Value of Manganese-Enhanced T1- and T2-Weighted MR Cholangiography for Differentiating Cystic Parenchymal Lesions from Cystic Abnormalities which Communicate with Bile Ducts
We present a case report to show how manganese-enhanced T1- and T2-weighted MR cholangiography could differentiate cystic parenchymal lesions from cystic abnormalities which communicate with the bile ducts
Strain-induced topological insulator phase and effective magnetic interactions in Li2IrO3
We present an effective tight-binding Hamiltonian for Li2IrO3 based on maximally localized Wannier functions for states near the Fermi level as obtained from first-principles electronic structure calculations. The majority of the Wannier orbitals are positioned on the center site with dominant j(eff) = 1/2 character, while relatively small j(eff) = 3/2 tails lie on the three nearest-neighbor sites. Interestingly, the spin quantization axis of the j(eff) = 1/2 components deviates from the local octahedral axis and points toward the nearest-neighbor Ir direction. In our tight-binding model, there are relatively strong next-nearest- and the third-nearest-neighbor hopping terms within the two-dimensional Ir honeycomb lattice in addition to the relatively small but significant interlayer hopping terms. The ratio between the nearest-neighbor and the third-nearest-neighbor hoppings, which can be controlled by the lattice strain, plays a critical role in determinating the Z(2)-invariant character of Li2IrO3. From our tight-binding model, we also derive an effective Hamiltonian and its parameters for the magnetic exchange interactions. Due to the complex spin-dependent next-nearest-neighbor hopping terms, our pseudospin Hamiltonian includes significant next-nearest-neighbor antiferromagnetic Kitaev terms as well as Dzyaloshinskii-Moriya and Heisenberg interactions. From our model Hamiltonian we estimate classical energies of collinear magnetic configurations as functions of the Hund's coupling of the Ir atom, from which zigzag-type magnetic order gives the lowest energy. DOI: 10.1103/PhysRevB.87.165117close11
Spin-Orbital Locking, Emergent Pseudo-Spin, and Magnetic order in Honeycomb Lattice Iridates
The nature of the effective spin Hamiltonian and magnetic order in the
honeycomb iridates is explored by considering a trigonal crystal field effect
and spin-orbit coupling. Starting from a Hubbard model, an effective spin
Hamiltonian is derived in terms of an emergent pseudo-spin-1/2 moment in the
limit of large trigonal distortions and spin-orbit coupling. The present
pseudo-spins arise from a spin-orbital locking and are different from the jeff
= 1/2 moments that are obtained when the spin-orbit coupling dominates and
trigonal distortions are neglected. The resulting spin Hamiltonian is
anisotropic and frustrated by further neighbour interactions. Mean field theory
suggests a ground state with 4-sublattice zig-zag magnetic order in a parameter
regime that can be relevant to the honeycomb iridate compound Na2IrO3, where
similar magnetic ground state has recently been observed. Various properties of
the phase, the spin-wave spectrum and experimental consequences are discussed.
The present approach contrasts with the recent proposals to understand iridate
compounds starting from the strong spin-orbit coupling limit and neglecting
non-cubic lattice distortions.Comment: 13 pages (Draft expanded; references updated; typos corrected and
discussion on recent experiments added
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