3,180 research outputs found
Pairing via Index theorem
This work is motivated by a specific point of view: at short distances and
high energies the undoped and underdoped cuprates resemble the -flux phase
of the t-J model. The purpose of this paper is to present a mechanism by which
pairing grows out of the doped -flux phase. According to this mechanism
pairing symmetry is determined by a parameter controlling the quantum tunneling
of gauge flux quanta. For zero tunneling the symmetry is ,
while for large tunneling it is . A zero-temperature critical
point separates these two limits
Composite fermions from the algebraic point of view
Composite fermion wavefuctions have been used to describe electrons in a
strong magnetic field. We show that the polynomial part of these wavefunctions
can be obtained by applying a normal ordered product of suitably defined
annihilation and creation operators to an even power of the Vandermonde
determinant, which can been considered as a kind of a non-trivial Fermi sea. In
the case of the harmonic interaction we solve the system exactly in the lowest
Landau level. The solution makes explicit the boson-fermion correspondence
proposed recently.Comment: 11 pages 1 figur
Pairing in High Temperature Superconductors and Berry Phase
The topological approach to the understanding of pairing mechanism in high
superconductors analyses the relevance of the Berry phase factor in this
context. This also gives the evidence for the pairing mechanism to be of
magnetic origin.Comment: 6 page
Mottness: Identifying the Propagating Charge Modes in doped Mott Insulators
High-temperature superconductivity in the copper-oxide ceramics remains an
unsolved problem because we do not know what the propagating degrees of freedom
are in the normal state. As a result, we do not know what are the weakly
interacting degrees of freedom which pair up to form the superconducting
condensate. That the electrons are not the propagating degrees of freedom in
the cuprates is seen most directly from experiments that show spectral weight
redistributions over all energy scales. Of course, the actual propagating
degrees of freedom minimize such spectral rearrangements. This review focuses
on the range of epxerimental consequences such UV-IR mixings have on the normal
state of the cuprates, such as the pseudogap, mid-infrared band, temperature
dependence of the Hall number, the superfluid density, and a recent theoretical
advance which permits the identification of the weakly interacting degrees of
freedom in a doped Mott insulator. Within this theory, we show how the wide
range of phenomena which typify the normal state of the cuprates arises
including linear resistivity.Comment: To appear as a Colloquium in the April issue of Rev. Mod. Phys
Updated version contains new references and a clarification concerning Fig.
8
Spin Hall Effect and Spin Transfer in Disordered Rashba Model
Based on numerical study of the Rashba model, we show that the spin Hall
conductance remains finite in the presence of disorder up to a characteristic
length scale, beyond which it vanishes exponentially with the system size. We
further perform a Laughlin's gauge experiment numerically and find that all
energy levels cannot cross each other during an adiabatic insertion of the flux
in accordance with the general level-repulsion rule. It results in zero spin
transfer between two edges of the sample as each state always evolves back
after the insertion of one flux quantum, in contrast to the quantum Hall
effect. It implies that the topological spin Hall effect vanishes with the
turn-on of disorder.Comment: 4 pages, 4 figures final versio
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