1,130 research outputs found
Kondo effect in the presence of spin-orbit coupling
We study the T=0 Kondo physics of a spin-1/2 impurity in a
non-centrosymmetric metal with spin-orbit interaction. Within a simple
variational approach we compute ground state properties of the system for an
{\it arbitrary} form of spin-orbit coupling consistent with the crystal
symmetry. This coupling produces an unscreened impurity magnetic moment and can
lead to a significant change of the Kondo energy. We discuss implications of
this finding both for dilute impurities and for heavy-fermion materials without
inversion symmetry.Comment: TeXLive (Unix), revtex4-1, 5 page
Quantum group covariant noncommutative geometry
The algebraic formulation of the quantum group covariant noncommutative
geometry in the framework of the -matrix approach to the theory of quantum
groups is given. We consider structure groups taking values in the quantum
groups and introduce the notion of the noncommutative connections and
curvatures transformed as comodules under the "local" coaction of the structure
group which is exterior extension of . These noncommutative
connections and curvatures generate -covariant quantum algebras.
For such algebras we find combinations of the generators which are invariants
under the coaction of the "local" quantum group and one can formally consider
these invariants as the noncommutative images of the Lagrangians for the
topological Chern-Simons models, non-abelian gauge theories and the Einstein
gravity. We present also an explicit realization of such covariant quantum
algebras via the investigation of the coset construction
.Comment: 21 pages, improved versio
Heavy antiferromagnetic phases in kondo lattices
We propose a microscopic physical mechanism that stabilizes the coexistence of the Kondo effect and antiferromagnetism in heavy-fermion systems. We consider a two-dimensional quantum Kondo-Heisenberg lattice model and show that long-range electron hopping leads to a robust antiferromagnetic Kondo state. By using a modified slave-boson mean-field approach we analyze the stability of the heavy antiferromagnetic phase across a range of parameters, and discuss transitions between different phases. Our results may be used to guide future experiments on heavy fermion compounds. © 2013 American Physical Society
Generalized Density Matrix Revisited: Microscopic Approach to Collective Dynamics in Soft Spherical Nuclei
The generalized density matrix (GDM) method is used to calculate
microscopically the parameters of the collective Hamiltonian. Higher order
anharmonicities are obtained consistently with the lowest order results, the
mean field [Hartree-Fock-Bogoliubov (HFB) equation] and the harmonic potential
[quasiparticle random phase approximation (QRPA)]. The method is applied to
soft spherical nuclei, where the anharmonicities are essential for restoring
the stability of the system, as the harmonic potential becomes small or
negative. The approach is tested in three models of increasing complexity: the
Lipkin model, model with factorizable forces, and the quadrupole plus pairing
model.Comment: submitted to Physical Review C on 08 May, 201
On quantum matrix algebras satisfying the Cayley-Hamilton-Newton identities
The Cayley-Hamilton-Newton identities which generalize both the
characteristic identity and the Newton relations have been recently obtained
for the algebras of the RTT-type. We extend this result to a wider class of
algebras M(R,F) defined by a pair of compatible solutions of the Yang-Baxter
equation. This class includes the RTT-algebras as well as the Reflection
equation algebras
Spectral extension of the quantum group cotangent bundle
The structure of a cotangent bundle is investigated for quantum linear groups
GLq(n) and SLq(n). Using a q-version of the Cayley-Hamilton theorem we
construct an extension of the algebra of differential operators on SLq(n)
(otherwise called the Heisenberg double) by spectral values of the matrix of
right invariant vector fields. We consider two applications for the spectral
extension. First, we describe the extended Heisenberg double in terms of a new
set of generators -- the Weyl partners of the spectral variables. Calculating
defining relations in terms of these generators allows us to derive SLq(n) type
dynamical R-matrices in a surprisingly simple way. Second, we calculate an
evolution operator for the model of q-deformed isotropic top introduced by
A.Alekseev and L.Faddeev. The evolution operator is not uniquely defined and we
present two possible expressions for it. The first one is a Riemann theta
function in the spectral variables. The second one is an almost free motion
evolution operator in terms of logarithms of the spectral variables. Relation
between the two operators is given by a modular functional equation for Riemann
theta function.Comment: 38 pages, no figure
Orbital order and Hund\u27s rule frustration in Kondo lattices
We analyze a microscopic origin of the Kondo effect-assisted orbital order in heavy-fermion materials. By studying the periodic two-orbital Anderson model with two local electrons, we show that frustration of Hund\u27s rule coupling due to the Kondo effect leads to an incommensurate spiral orbital and magnetic order, which exists only inside the Kondo screened (heavy-electron) phase. This spiral state can be observed in neutron and resonant x-ray scattering measurements in U- and Pr-based heavy-fermion compounds, and realized in cold atomic gases, e.g., fermionic Yb173. © 2013 American Physical Society
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