6,259 research outputs found
Magnetotransport of Dirac Fermions on the surface of a topological insulator
We study the properties of Dirac fermions on the surface of a topological
insulator in the presence of crossed electric and magnetic fields. We provide
an exact solution to this problem and demonstrate that, in contrast to their
counterparts in graphene, these Dirac fermions allow relative tuning of the
orbital and Zeeman effects of an applied magnetic field by a crossed electric
field along the surface. We also elaborate and extend our earlier results on
normal metal-magnetic film-normal metal (NMN) and normal metal-barrier-magnetic
film (NBM) junctions of topological insulators [Phys. Rev. Lett. {\bf 104},
046403 (2010)]. For NMN junctions, we show that for Dirac fermions with Fermi
velocity , the transport can be controlled using the exchange field
of a ferromagnetic film over a region of width . The
conductance of such a junction changes from oscillatory to a monotonically
decreasing function of beyond a critical which leads to the
possible realization of magnetic switches using these junctions. For NBM
junctions with a potential barrier of width and potential , we find
that beyond a critical , the criteria of conductance maxima
changes from to for
integer . Finally, we compute the subgap tunneling conductance of a normal
metal-magnetic film-superconductor (NMS) junctions on the surface of a
topological insulator and show that the position of the peaks of the zero-bias
tunneling conductance can be tuned using the magnetization of the ferromagnetic
film. We point out that these phenomena have no analogs in either conventional
two-dimensional materials or Dirac electrons in graphene and suggest
experiments to test our theory.Comment: 11 pages, 12 figures; v
Tuning the conductance of Dirac fermions on the surface of a topological insulator
We study the transport properties of the Dirac fermions with Fermi velocity
on the surface of a topological insulator across a ferromagnetic strip
providing an exchange field over a region of width . We show
that the conductance of such a junction changes from oscillatory to a
monotonically decreasing function of beyond a critical . This
leads to the possible realization of a magnetic switch using these junctions.
We also study the conductance of these Dirac fermions across a potential
barrier of width and potential in the presence of such a
ferromagnetic strip and show that beyond a critical , the
criteria of conductance maxima changes from
to for integer . We point out that these novel phenomena
have no analogs in graphene and suggest experiments which can probe them.Comment: v1 4 pages 5 fig
Emperipolesis in a Case of Adult T Cell Lymphoblastic Lymphoma (Mediastinal type)-Detected at FNAC and Imprint Cytology
Emperipolesis is a condition in which viable hematopoetic cells are seen intact in the cytoplasm of host cell without damage. This phenomenon is seen in many physiologic and pathologic conditions, its presence in Rosai Dorfman disease (RDD) is characteristic of the disease. However emperipolesis is an uncommon finding in malignant lymphoma both Hodgkins and non-Hodgkin’s lymphoma, wherein it has been described in bone marrow aspirate and tissue culture. In contrast there are only two case reports of emperipolesis phenomenon described in non-Hodgkin’s lymphoma in tissue sections. We report a case of an adult T cell lymphoblastic lymphoma (mediastinal type) with features of emperipolesis demonstrated at fine needle aspiration cytology (FNAC) and imprint cytology of cervical lymph nodes. To our knowledge, this is the first case report of emperipolesis in a case of adult T cell lymphoblastic lymphoma (mediastinal type)-detected at FNAC and imprint cytology
Magnetic phenomena at and near nu =1/2 and 1/4: theory, experiment and interpretation
I show that the hamiltonian theory of Composite Fermions (CF) is capable of
yielding a unified description in fair agreement with recent experiments on
polarization P and relaxation rate 1/T_1 in quantum Hall states at filling nu =
p/(2ps+1), at and near nu = 1/2 and 1/4, at zero and nonzero temperatures. I
show how rotational invariance and two dimensionality can make the underlying
interacting theory behave like a free one in a limited context.Comment: Latex 4 pages, 2 figure
A stable Algebraic Spin Liquid in a Hubbard model
We show the existence of a stable Algebraic Spin Liquid (ASL) phase in a
Hubbard model defined on a honeycomb lattice with spin-dependent hopping that
breaks time-reversal symmetry. The effective spin model is the Kitaev model for
large on-site repulsion. The gaplessness of the emergent Majorana fermions is
protected by the time reversal (TR) invariance of this model. We prove that the
effective spin model is TR invariant in the entire Mott phase thus ensuring the
stability of the ASL. The model can be physically realized in cold atom systems
and we propose experimental signals of the ASL.Comment: Published in PR
Herbal vs. Chemical Actives as Antidandruff Ingredients -Which Are More Effective in the Management of Dandruff?– An Overview
Dandruff, a clinical condition caused by Malassezia (Pityrosporum) species is of great cosmetic concern all over the world. Dandruff is known to be controlled by fungistatic ingredients in Anti-dandruff shampoos. A comparative study on the efficacy of chemical and herbal anti-dandruff ingredients on ‘as is’ basis and their performance in market shampoos was done in vitro against Pityrosporum ovale (MTCC 1374). Zinc pyrithione (ZnPTO), ketoconazole and other azole compounds recorded good anti-Pityrosporum activity among the chemical ingredients. Herbal ingredients like tea tree oil, rosemary oil, coleus oil, clove oil, pepper extract, neem extract, and basil extract also recorded anti-pityrosporum activity, but their MIC values are much higher than the synthetic ingredients. Shampoos containing ZnPTO and ketoconazole recorded higher in vitro activities than the shampoos containing herbal AD ingredients
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