Motion Of Single Hole Research Articles

Magnon dispersion and single hole motion in 2D frustrated antiferromagnets with four-sublattice structures

We study a two dimensional spin-12J1–J2 antiferromagnet in a square lattice using the linearized spin wave theory recognizing the 4-sublattice nature of the underlying magnetic lattice. Multiple magnon modes with optical and acoustic branches about the stable Neel ordered and double acoustic branches about the columnar reference states are obtained for small and large values of λ(=J2/J1) respectively. An additional uniaxial anisotropy, for large λ, can lead to distinct spin gaps in such systems, as also witnessed experimentally. The single hole spectral behavior in a 2D t–J1–J2 model, for small frustration, is then calculated within the non-crossing approximation. Our results match fairly well with exact diagonalization results from a 4×4 cluster. Hole spectral features and their evolution with λ resulting in “water-fall”-like smooth spectral weight transfer are discussed. Hole energy bands are identified and the corresponding energy-shift and reduction in width with spin-frustration are indicated.

Strong correlation induced charge localization in antiferromagnets

The fate of a hole injected in an antiferromagnet is an outstanding issue of strongly correlated physics. It provides important insights into doped Mott insulators closely related to high-temperature superconductivity. Here, we report a systematic numerical study of t-J ladder systems based on the density matrix renormalization group. It reveals a surprising result for the single hole's motion in an otherwise well-understood undoped system. Specifically, we find that the common belief of quasiparticle picture is invalidated by the self-localization of the doped hole. In contrast to Anderson localization caused by disorders, the charge localization discovered here is an entirely new phenomenon purely of strong correlation origin. It results from destructive quantum interference of novel signs picked up by the hole, and since the same effect is of a generic feature of doped Mott physics, our findings unveil a new paradigm which may go beyond the single hole doped system.

Remnant Fermi surface in a pseudogap regime of the two-dimensional Hubbard model at finite temperature

A precursor effect on the Fermi surface in the two-dimensional Hubbard model at finite temperatures near the antiferromagnetic instability is studied using three different itinerant approaches: the second order perturbation theory, the paramagnon theory (PT), and the two-particle self-consistent (TPSC) approach. In general, at finite temperature, the Fermi surface of the interacting electron systems is not sharply defined due to the broadening effects of the self-energy. In order to take account of those effects we consider the single-particle spectral function A( , 0) at the Fermi level, to describe the counterpart of the Fermi surface at T = 0. We find that the Fermi surface is destroyed close to the pseudogap regime due to the spin-fluctuation effects in both PT and TPSC approaches. Moreover, the top of the effective valence band is located around = (π/2,π/2) in agreement with earlier investigations on the single-hole motion in the antiferromagnetic background. A crossover behavior from the Fermi-liquid regime to the pseudogap regime is observed in the electron concentration dependence of the spectral function and the self-energy.

Theory of excitons in the insulatingCu−O2plane

We use a local model to study the formation and the structure of the low-energy charge-transfer excitations in the insulating ${\mathrm{C}\mathrm{u}\ensuremath{-}\mathrm{O}}_{2}$ plane. The elementary excitation is a bound exciton of spin singlet, consisting of a ${\mathrm{Cu}}^{+}$ and a neighboring spin singlet of Cu-O holes. The exciton can move through the lattice freely without disturbing the antiferromagnetic spin background, in contrast to the single hole motion. There are four eigenmodes of excitons with different symmetry. The $p$-wave-like exciton has a large dispersion width. The $s$-wave-like exciton mixes with the $p$ state at finite momentum, and its dipole transition intensity is strongly anisotropic. The model is in excellent agreement with the electron energy-loss spectra in the insulating ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{2}{\mathrm{Cl}}_{2}.$

Motion of single hole in the framework of the emery model equivalence to the : -J model

We have argued for the validity of the Zhang-Rice renormalization procedure for motion of a hole in CuO 2 planes in the low-energy range of spectrum. It is shown that in the J m limit of the Emery model the spectrum of a hole. Moving in an antiferromagnetic background, is strongly renormalized by spin excitations.

Neutron hole states in theN=81 nuclei

The energy spectra of theN=81 nuclei have been calculated by coupling the neutron single-hole motion to the quadrupole vibrations of the nuclear surface. The wave functions are used to calculateM1 andE2 moments. Gamma-ray branching ratios are extensively discussed and compared with the many experimental data on 54 135 Xe81, 58 139 Ce81 and 60 141 Nd81. Also spectroscopic factors for (p,d) reactions have been calculated and compared to experimental single-neutron pick-up reactions. The excitation energy and the lifetime of the isomeric stateπ π, decaying by anM4 transition, are studied, in particular in their dependence on the number of extra protons. The behaviour of the centroid of the neutron single-hole energies as a function of the number of extra protons is calculated with a delta force for the neutron-proton interaction.