Description
Poster presenters:
BALLMANN, Katinka:
Mr. BAUER, Florian:
Mr. BEUGELING, Wouter:
Chern-Simons theory of multi-component quantum Hall
systems
The fractional quantum Hall effect is conveniently described
by a
Chern-Simons based composite-fermion approach. The
Hamiltonian theory of
Shankar and Murthy [Rev. Mod. Phys. 75, 1101 (2003)]
proves to be a
useful model to compute physical quantities.
On this poster we present an extension of this model to
systems for
which internal degrees of freedom (spin and pseudospin) are
relevant,
such as bilayer systems and graphene.
Mr. BRANDINO, Giuseppe Piero:
Energy level distribution of perturbed
conformal field theories
We study the energy level spacing of perturbed conformal
minimal
models in finite volume, considering perturbations of such
models that are
massive but not necessarily integrable. We compute their
spectrum using a
renormalization group improved truncated conformal
spectrum approach. With
this method we are able to study systems where more than
40 000 states are kept
and where we determine the energies of the lowest several
thousand eigenstates
with high accuracy. We find, as expected, that the level
spacing statistics of
integrable perturbed minimal models are Poissonian while
the statistics of nonintegrable
perturbations are GOE-like. However, by varying the system
size (and so controlling the
positioning of the theory between its IR and UV limits) one
can induce crossovers between
the two statistical distributions.
Mr. CAGNANI, Ivan:
Ms. CANOVI, Elena:
We discuss how thermalization following a quantum quench
in a strongly
correlated quantum system is intimately connected to
many-body
localization in the space of quasi-particles. We test our
picture in the
anisotropic Heisenberg spin chain with an integrability-
breaking term. We
first quantify the deviations from integrability by analyzing
the level
spacing statistics and the charac- teristics of the system
eigenstates. We
then focus on thermalization by studying the dynamics
after a sudden
quench of the anisotropy parameter.
arXiv:1006.1634
Dr. CHUDZINSKI, Piotr:
Spin rotational symmetry breaking by orbital current
patterns in
two-leg ladders
P. Chudzinski, M. Gabay, and T. Giamarchi
We investigate the physical consequences of orbital current
patterns
(OCP) in doped two-leg Cu-O Hubbard ladders. The internal
symmetry of
the pattern, in the case of the ladder structure, differs
slightly
from that suggested so far for cuprates. We focus on this
OCP and look
for measurable signatures of its existence. We compute the
magnetic
field produced by the OCP at each lattice site and estimate
its value
in view of a possible experimental detection. Using a
renormalization-group (RG) analysis, we determine the
changes that are
caused by the SU(2) spin rotational symmetry breaking
which occurs
when the OCP is present in the ground-state phase
diagram. The most
significant one is an in-plane spin-density wave gap opening
in an
otherwise critical phase, at intermediate dopings. We
estimate the
value of this gap, give an analytic expression for the
correlation
functions and examine some of the magnetic properties of
this new
phase which can be revealed in measurements. We
compute the
conductance in the presence of a single impurity using an
RG analysis.
A discussion of the various sources of SU(2) symmetry
breaking
underscores the specificity of the OCP-induced effects.
Mr. DALMONTE, Marcello:
Atomic color superfluidity via three-body loss
Large three-body loss rates in a three-component Fermi gas
confined in an optical lattice can dynamically
prevent atoms from
tunneling so as to occupy a lattice site with three atoms.
This effective constraint not only suppresses the
occurrence of
actual loss events, but stabilizes color-like BCS-pairing
phases by suppressing the formation of trions. We
study the effect of
the constraint on the many-body physics using bosonization
and density matrix renormalization group
techniques, and also
investigate the full dissipative dynamics including loss for
the example of $^6$Li.
A. Kantian, M. Dalmonte, S. Diehl, W. Hofstetter, P. Zoller
and A. J. Daley, Phys. Rev. Lett. {\bf 104}, 240401
(2009)
Mr. DE LUCA, Andrea:
Prof. EGGERT, Sebastian:
Dr. ERMANN, Leonardo:
Dr. ESTIENNE, Benoit:
Electron-quasihole duality in Read-Rezayi states and Jack
wavefunctions
We consider the quasihole wavefunctions of the non-abelian
Read-Rezayi quantum Hall states which are given by the
conformal
blocks of the minimal model WA_{k-1}(k+1,k+2) of the
WA_{k-1} algebra. By studying the degenerate
representations of this
conformal field theories, we derive a second order
differential equation satisfied by a general many-quasihole
wavefunction. We
find a duality between the differential equations fixing the
electron and quasihole wavefunctions. They both satisfy the
Laplace-
Beltrami equation. We use this equation to obtain an
analytic expression for the generic wavefunction with one
excess flux.
These results also apply to the more general models
WA_{k-1}(k+1,k+r) corresponding to the recently
introduced Jack states
Mr. FAGOTTI, Maurizio:
Mr. FERRARO, Dario:
Multiple-quasiparticles tunnelling between fractional
quantum Hall edge states
A detailed description of tunnelling processes through a
point contact for fractional quantum Hall edges in the Jain
series will be
presented. Edge states will be
described in terms of charged and neutral modes
propagating with finite velocities. Possible interaction effects
due to external
environment will be properly
taken into account.
We will show that multiple-quasiparticle agglomerates
dominate on single quasiparticle in the low energy regime.
This result
crucially depends on the presence
of finite bandwidth neutral modes and is essential to explain
the observed anomalous behaviour of tunnelling
conductance and
noise through a point contact
[1, 2]. The temperature behaviour of linear conductance
and effective charge estimated from the current noise will
be presented
and compared with
experiments [3, 4, 5].
[1] Y.C. Chung, M. Heiblum, V. Umansky, Phys. Rev. Lett.
91, 216804 (2003).
[2] A. Bid, N. Ofek, M. Heiblum, V. Umansky, D. Mahalu,
Phys. Rev. Lett. 103, 236802 (2009).
[3] D. Ferraro, A. Braggio, M. Merlo, N. Magnoli, M. Sassetti,
Phys. Rev. Lett. 101, 166805 (2008).
[4] D. Ferraro, A. Braggio, N. Magnoli, M. Sassetti, New J.
Phys. 12, 013012 (2010).
Mr. FIORETTO, Davide:
Quantum quenches in integrable field theories
We study the non equilibrium time evolution of an
integrable
field theory in 1+1 dimensions after a sudden variation of a
global
parameter of the Hamiltonian. For a specific class of
quenches, we compute
the expectation value of any local operators for long times
as a series of
form factors. In this way, we are able to show that this
asymptotic value
can be obtained by a generalized Gibbs ensemble with a
different effective
temperature for each eigenmode.
Dr. FRANCHINI, Fabio:
Nonlinear dynamics of spin and charge in spin-Calogero
model
We study the full, nonlinear dynamics of spin and charge in
the
spin-Calogero model, by constructing a collective, i.e.
hydrodynamic,
description of the model.
The latter is an integrable 1-D model of quantum spin-1/2
particles
interacting through inverse-square interaction and
exchange.
We construct the collective Hamiltonian in a semi-classical
regime where
gradient corrections to the exact hydrodynamic formulation
of the theory
may be neglected.
In this approximation, the equations of motion can be
decoupled and
written as to a set of independent Riemann-Hopf (or inviscid
Burgers')
equations for the dressed Fermi momenta.
We study the dynamics of some non-equilibrium spin-
charge configurations
for times smaller than the time-scale of the gradient
catastrophe and we
find an interesting interplay between spin and charge
degrees of freedom.
We also consider the limit of large coupling parameter and
show that the
resulting hydrodynamics for the spin sector describes the
so-called
Haldane-Shastry model.
Finally, we show how this hydrodynamic description allows
for the
calculation of correlation functions that cannot be
considered with
conventional bosonization, such as the Emptiness
Formation Probability.
- M. Kulkarni, F. Franchini, A. G. Abanov; Physical Review B
80, 165105
(2009)
- F. Franchini, M. Kulkarni; Nucl.Phys.B825:320-340,2010
Dr. GARCIA GARCIA, antonio:
Mr. GHAZARYAN, Areg:
Dr. SATO, Masahiro:
Spin dynamics in multipolar phases of one-dimensional
quantum frustrated ferromagnet
Recently, it has been shown that spin
nematic (quadrupolar) or higher multipolar correlation
functions exhibit
a quasi long- range order in the broad range of the field-
induced
Tomonaga-Luttinger-liquid (TLL) phase in spin-1/2
frustrated chains.
We show [1,2] that the temperature and field dependence
of the NMR relaxation rate
1/T1 in these multipolar TLLs is qualitatively different from
that
in conventional TLLs of one-dimensional quantum magnets
such
as the spin-1/2 Heisenberg chain; 1/T1 decreases with
lowering temperature
in high-field region of multipolar TLL, and it also decreases
with increasing
a magnetic field. These behaviors can be used as an indirect
but
definite signature for identifying the multipolar order. We
also discuss
some characteristic features of spin dynamical structure
factors.
[1] M.Sato, T.Momoi and A.Furusaki, PRB79, 060406(R)
(2009).
[2] M.Sato, T.Hikihara and T.Momoi, in preparation.
