13,229 research outputs found
Supersymmetric Reciprocal Transformation and Its Applications
The supersymmetric analog of the reciprocal transformation is introduced.
This is used to establish a transformation between one of the supersymmetric
Harry Dym equations and the supersymmetric modified Korteweg-de Vries equation.
The reciprocal transformation, as a B\"{a}cklund-type transformation between
these two equations, is adopted to construct a recursion operator of the
supersymmetric Harry Dym equation. By proper factorization of the recursion
operator, a bi-Hamiltonian structure is found for the supersymmetric Harry Dym
equation. Furthermore, a supersymmetric Kawamoto equation is proposed and is
associated to the supersymmetric Sawada-Kotera equation. The recursion operator
and odd bi-Hamiltonian structure of the supersymmetric Kawamoto equation are
also constructed.Comment: 31 pages, expande
A non-standard Lax formulation of the Harry Dym hierarchy and its supersymmetric extension
For the Harry Dym hierarchy, a non-standard Lax formulation is deduced from
that of Korteweg-de Vries (KdV) equation through a reciprocal transformation.
By supersymmetrizing this Lax operator, a new N=2 supersymmetric extension of
the Harry Dym hierarchy is constructed, and is further shown to be linked to
one of the N=2 supersymmetric KdV equations through superconformal
transformation. The bosonic limit of this new N=2 supersymmetric Harry Dym
equation is related to a coupled system of KdV-MKdV equations.Comment: 9 page
Superconducting correlations in ultra-small metallic grains
To describe the crossover from the bulk BCS superconductivity to a
fluctuation-dominated regime in ultrasmall metallic grains, new order
parameters and correlation functions, such as ``parity gap'' and ``pair-mixing
correlation function'', have been recently introduced. In this paper, we
discuss the small-grain behaviour of the Penrose-Onsager-Yang off-diagonal
long-range order (ODLRO) parameter in a pseudo-spin representation. Relations
between the ODLRO parameter and those mentioned above are established through
analytical and numerical calculations.Comment: 7 pages, 1 figur
Phase transitions and iron-ordered moment form factor in LaFeAsO
Elastic neutron scattering studies of an optimized LaFeAsO single crystal
reveal that upon cooling, an onset of the tetragonal (T)-to-orthorhombic (O)
structural transition occurs at K, and it exhibits a
sharp transition at K. We argue that in the
temperature range to , T and O structures may
dynamically coexist possibly due to nematic spin correlations recently proposed
for the iron pnictides, and we attribute to the formation of
long-range O domains from the finite local precursors. The antiferromagnetic
structure emerges at K, with the iron moment
direction along the O \emph{a} axis. We extract the iron magnetic form factor
and use the tabulated of Fe, Fe and Fe to
obtain a magnetic moment size of 0.8 at 9.5 K.Comment: 7 pages, 6 figures, 3 table
Robust and clean Majorana zero mode in the vortex core of high-temperature superconductor (Li0.84Fe0.16)OHFeSe
The Majorana fermion, which is its own anti-particle and obeys non-abelian
statistics, plays a critical role in topological quantum computing. It can be
realized as a bound state at zero energy, called a Majorana zero mode (MZM), in
the vortex core of a topological superconductor, or at the ends of a nanowire
when both superconductivity and strong spin orbital coupling are present. A MZM
can be detected as a zero-bias conductance peak (ZBCP) in tunneling
spectroscopy. However, in practice, clean and robust MZMs have not been
realized in the vortices of a superconductor, due to contamination from
impurity states or other closely-packed Caroli-de Gennes-Matricon (CdGM)
states, which hampers further manipulations of Majorana fermions. Here using
scanning tunneling spectroscopy, we show that a ZBCP well separated from the
other discrete CdGM states exists ubiquitously in the cores of free vortices in
the defect free regions of (Li0.84Fe0.16)OHFeSe, which has a superconducting
transition temperature of 42 K. Moreover, a Dirac-cone-type surface state is
observed by angle-resolved photoemission spectroscopy, and its topological
nature is confirmed by band calculations. The observed ZBCP can be naturally
attributed to a MZM arising from this chiral topological surface states of a
bulk superconductor. (Li0.84Fe0.16)OHFeSe thus provides an ideal platform for
studying MZMs and topological quantum computing.Comment: 32 pages, 15 figures (supplementary materials included), accepted by
PR
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