8,002 research outputs found
Spin-orbit and impurity scattering in an integrable electron model: Exact results for dynamic correlations
We introduce an integrable model of spin-polarized interacting electrons
subject to a spin-conserving spin-orbit interaction. Using Bethe Ansatz and
conformal field theory we calculate the exact large-time single-electron and
density correlations and find that while the spin-orbit interaction enhances
the single-electron Green's function, the density correlations get suppressed.
Adding a localized impurity and coupling it to the electrons so that
integrability is preserved, the dynamic correlations are found to change
significantly after a quantum quench with the impurity interaction switched on
suddenly. When the electrons are confined to a periodic structure, the
correlations are indifferent to the location of the impurity and only carry an
imprint of its intrinsic properties. We conjecture that this unusual feature
originates from the integrability of the model.Comment: 8 pages, 1 figur
Kodaira Dimension of Subvarieties
In this article we study how the birational geometry of a normal projective
variety is influenced by a normal subvariety One of the most
basic examples in this context is provided by the following situation. Let
be a surjective holomorphic map with connected fibers between
compact connected complex manifolds. It is well known that given a general
fiber of we have This article grew
out of the realization that this result should be true with replaced
by the codimension \cod_X A for a pair consisting of a normal
subvariety of a compact normal variety under weak semipositivity
conditions on the normal sheaf of and the weak singularity condition
\cod_A (A\cap\sing X)\ge 2. We shall now state our main results in the
special case of a submanifold in a projective manifold and we also
simplify the semipositivity notion
Perturbation theories for the S=1/2 spin ladder with four-spin ring exchange
The isotropic S=1/2 antiferromagnetic spin ladder with additional four-spin
ring exchange is studied perturbatively in the strong coupling regime with the
help of cluster expansion technique, and by means of bosonization in the weak
coupling limit. It is found that a sufficiently large strength of ring exchange
leads to a second-order phase transition, and the shape of the boundary in the
vicinity of the known exact transition point is obtained. The critical exponent
for the gap is found to be , in agreement both with exact results
available for the dimer line and with the bosonization analysis. The phase
emerging for high values of the ring exchange is argued to be gapped and
spontaneously dimerized. The results for the transition line from strong
coupling and from weak coupling match with each other naturally.Comment: 8 pages, 4 figures, some minor changes in text and reference
Tunneling between helical Majorana modes and helical Luttinger liquids
We propose and study the charge transport through single and double quantum
point contacts setup between helical Majorana modes and an interacting helical
Luttinger liquid. We show that the differential conductance decreases for
stronger repulsive interactions and that the point contacts become insulating
above a critical interaction strength. For a single point contact, the
differential conductance as a function of bias voltage shows a series of peaks
due to Andreev reflection of electrons in the Majorana modes. In the case of
two point contacts, interference phenomena make the structure of the individual
resonance peaks less universal and show modulations with different separation
distance between the contacts. For small separation distance the overall
features remain similar to the case of a single point contact.Comment: v.2: 14 pages, 11 figures; adding one figure, an appendix, and some
minor change
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