143 research outputs found
Competing orders in the generalized Hund chain model at half-filling
By using a combination of several non-perturbative techniques -- a
one-dimensional field theoretical approach together with numerical simulations
using density matrix renormalization group -- we present an extensive study of
the phase diagram of the generalized Hund model at half-filling. This model
encloses the physics of various strongly correlated one-dimensional systems,
such as two-leg electronic ladders, ultracold degenerate fermionic gases
carrying a large hyperfine spin 3/2, other cold gases like Ytterbium 171 or
alkaline-earth condensates. A particular emphasis is laid on the possibility to
enumerate and exhaust the eight possible Mott insulating phases by means of a
duality approach. We exhibit a one-to-one correspondence between these phases
and those of the two-leg Hubbard ladder with interchain hopping. Our results
obtained from a weak coupling analysis are in remarkable quantitative agreement
with our numerical results carried out at moderate coupling.Comment: 26 pages, 14 figure
Symmetry-protected topological phases of alkaline-earth cold fermionic atoms in one dimension
We investigate the existence of symmetry-protected topological phases in
one-dimensional alkaline-earth cold fermionic atoms with general half-integer
nuclear spin I at half filling. In this respect, some orbital degrees of
freedom are required. They can be introduced by considering either the
metastable excited state of alkaline-earth atoms or the p-band of the optical
lattice. Using complementary techniques, we show that SU(2) Haldane topological
phases are stabilised from these orbital degrees of freedom. On top of these
phases, we find the emergence of topological phases with enlarged SU(2I+1)
symmetry which depend only on the nuclear spin degrees of freedom. The main
physical properties of the latter phases are further studied using a
matrix-product state approach. On the one hand, we find that these phases are
symmetry-protected topological phases, with respect to inversion symmetry, when
I=1/2,5/2,9/2,..., which is directly relevant to ytterbium and strontium cold
fermions. On the other hand, for the other values of I(=half-odd integer),
these topological phases are stabilised only in the presence of exact
SU(2I+1)-symmetry
Haldane charge conjecture in one-dimensional multicomponent fermionic cold atoms
A Haldane conjecture is revealed for spin-singlet charge modes in
2N-component fermionic cold atoms loaded into a one-dimensional optical
lattice. By means of a low-energy approach and DMRG calculations, we show the
emergence of gapless and gapped phases depending on the parity of for
attractive interactions at half-filling. The analogue of the Haldane phase of
the spin-1 Heisenberg chain is stabilized for N=2 with non-local string charge
correlation, and pseudo-spin 1/2 edge states. At the heart of this even-odd
behavior is the existence of a spin-singlet pseudo-spin operator which
governs the low-energy properties of the model for attractive interactions and
gives rise to the Haldane physics.Comment: 4 pages, 4 figure
Competing orders in one-dimensional half-filled multicomponent fermionic cold atoms: The Haldane-charge conjecture
We investigate the nature of the Mott-insulating phases of half-filled
2N-component fermionic cold atoms loaded into a one-dimensional optical
lattice. By means of conformal field theory techniques and large-scale DMRG
calculations, we show that the phase diagram strongly depends on the parity of
. First, we single out charged, spin-singlet, degrees of freedom, that carry
a pseudo-spin allowing to formulate a Haldane conjecture: for
attractive interactions, we establish the emergence of Haldane insulating
phases when is even, whereas a metallic behavior is found when is odd.
We point out that the cases do \emph{not} have the generic properties
of each family. The metallic phase for odd and larger than 1 has a
quasi-long range singlet pairing ordering with an interesting edge-state
structure. Moreover, the properties of the Haldane insulating phases with even
further depend on the parity of N/2. In this respect, within the low-energy
approach, we argue that the Haldane phases with N/2 even are not topologically
protected but equivalent to a topologically trivial insulating phase and thus
confirm the recent conjecture put forward by Pollmann {\it et al.} [Pollmann
{\it et al.}, arXiv:0909.4059 (2009)].Comment: 25 pages, 20 figure
Quantum criticality in the SO(5) bilinear-biquadratic Heisenberg chain
The zero-temperature properties of the SO(5) bilinear-biquadratic Heisenberg chain are investigated by means of a low-energy approach and large-scale numerical calculations. In sharp contrast to the spin-1 SO(3) Heisenberg chain, we show that the SO(5) Heisenberg chain is dimerized with a twofold degenerate ground state. On top of this gapful phase, we find the emergence of a nondegenerate gapped phase with hidden (Z(2) x Z(2))(2) symmetry and spin-3/2 edge states that can be understood from a SO(5) AKLT wave function. We derive a low-energy theory describing the quantum critical point which separates these two gapped phases. It is shown and confirmed numerically that this quantum critical point belongs to the SO(5)(1) universality class
miR-CATCH: microRNA capture affinity technology.
Several experimental methods exist to explore the microRNA (miRNA) regulome. These methods almost exclusively focus on multiple targets bound to a single, or perhaps a few miRNAs of interest. Here, we describe a microRNA capture affinity technology (miR-CATCH) which uses an affinity capture oligonucleotide to co-purify a single target messenger RNA (mRNA) together with all its endogenously bound miRNAs. This bench-top method is similar to RNA immunoprecipitation (RIP) and provides an experimental alternative to computational miRNA target prediction
Quantum Computing and Quantum Simulation with Group-II Atoms
Recent experimental progress in controlling neutral group-II atoms for
optical clocks, and in the production of degenerate gases with group-II atoms
has given rise to novel opportunities to address challenges in quantum
computing and quantum simulation. In these systems, it is possible to encode
qubits in nuclear spin states, which are decoupled from the electronic state in
the S ground state and the long-lived P metastable state on the
clock transition. This leads to quantum computing scenarios where qubits are
stored in long lived nuclear spin states, while electronic states can be
accessed independently, for cooling of the atoms, as well as manipulation and
readout of the qubits. The high nuclear spin in some fermionic isotopes also
offers opportunities for the encoding of multiple qubits on a single atom, as
well as providing an opportunity for studying many-body physics in systems with
a high spin symmetry. Here we review recent experimental and theoretical
progress in these areas, and summarise the advantages and challenges for
quantum computing and quantum simulation with group-II atoms.Comment: 11 pages, 7 figures, review for special issue of "Quantum Information
Processing" on "Quantum Information with Neutral Particles
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