Properties Of Skyrmions Research Articles

Electric field control of the skyrmion lattice in Cu2OSeO3

Small-angle neutron scattering has been employed to study the influence of applied electric (E-)fields on the skyrmion lattice in the chiral lattice magnetoelectric Cu2OSeO3. Using an experimental geometry with the E-field parallel to the [111] axis, and the magnetic field parallel to the [] axis, we demonstrate that the effect of applying an E-field is to controllably rotate the skyrmion lattice around the magnetic field axis. Our results are an important first demonstration for a microscopic coupling between applied E-fields and the skyrmions in an insulator, and show that the general emergent properties of skyrmions may be tailored according to the properties of the host system.

Is there a crystalline state of nuclear matter?

A possibility of the crystalline state of nuclear matter is discussed in a medium-modified Skyrme model. The interaction energy per nucleon in nuclear matter is evaluated by taking into account the medium influence on single nucleon–skyrmion properties and the tensor part of the nucleon–nucleon potential, and by using a variational method of Hartree–Fock type including zero-point quantum fluctuations. It is shown that in this approach the ground state of nuclear matter has no crystalline structure due to quantum fluctuations as well as medium modifications of hadron properties.

Skyrmion in nuclear matter

The properties of Skyrmions in finite nuclei are considered. The deformation effect is taken into account through the external-field-induced distortion of the profile function of a chiral field. The masses of classical Skyrmions and the distribution of their baryon number versus the Skyrmion position within a nucleus are discussed.

Topological Excitations in Spinor Bose-Einstein Condensates

We investigate the properties of skyrmion in the ferromagnetic state of spin-1 Bose-Einstein condensates by means of the mean-field theory and show that the size of a skyrmion is fixed to the order of the healing length. It is shown that the interaction between two skyrmions with oppositely rotating spin textures is attractive when their separation is large, following a unique power-law behavior with a power of -7/2.

The nucleus as a fluid of skyrmions: energy levels and nucleon properties in the medium

A model of a fluid of skyrmions coupled to a scalar and to the meson mean fields is developed. The central and spin-orbit potentials of a skyrmion generated by the fields predict correct energy levels in selected closed shell nuclei. The effect of the meson fields on the properties of skyrmions in nuclei is investigated.

Skyrmions as the ground states of quantum dots in strong magnetic fields

We note that the properties of skyrmions capture many features of the ground states of quantum dots in strong magnetic fields. Therefore, in the present work we choose skyrmions with high winding numbers as trial ground states. In our results, we find that the occurrence of skyrmions fits an instability criterion of maximum density droplet very well. Interesting spin structures are found and such structures are recently supported by electron spin resonance experiments. The addition spectrum is calculated and the transition found in recent experiments is attributable to anti-skyrmion to skyrmion transition. The implication of pair tunneling from our trial wave function is discussed.

SKYRMIONS IN QUANTUM HALL FERROMAGNETS

Properties of skyrmions in quantum Hall systems are reviewed. It is shown that, using a Hartree-Fock technique, the size of skyrmions near filling factor ν=1 may be computed, yielding a result in close agreement with experiment. Finite densities of skyrmions are shown to lead to a crystal state with square symmetry due to the spin-dependent nature of their mutual interactions. The square lattice state has an unusual spin ordering which leads to a new gapless mode, analogous to spin waves in a two-dimensional XY antiferromagnet. The stability of the ordered spin state is assessed using a time-dependent Hartree-Fock approach, and a phase diagram is derived which shows the parameter range for which long-range spin ordering is destroyed by quantum fluctuations.

Optics with Quantum Hall Skyrmions

A novel type of charged excitation, known as a Skyrmion, has recently been discovered in quantum Hall systems with filling factor near ν=1. A Skyrmion — which can be thought of as a topological twist in the spin density of the electron gas — has the same charge as an electron, but a much larger spin. In this review we present a detailed theoretical investigation of the optical properties of Skyrmions. Our results provide means for the optical detection of Skyrmions using photoluminescence (PL) spectroscopy. We first consider the optical properties of Skyrmions in disordered systems. A calculation of the luminescence energy reveals a special optical signature which allows us to distinguish between Skyrmions and ordinary electrons. Two experiments to measure the optical signature are proposed. We then turn to the optical properties of Skyrmions in pure systems. We show that, just like an ordinary electron, a Skyrmion may bind with a hole to form a Skyrmionic exciton. The Skyrmionic exciton can have a lower energy than the ordinary magnetoexciton. The optical signature of Skyrmions is found to be a robust feature of the PL spectrum in both disordered and pure systems.

Properties of skyrmions of large baryon number

Using a mixture of analytic and numerical techniques, the authors calculate the properties of skyrmions pertaining to large baryon number N. They find a closed-form approximation for the soliton profile and generate approximate expressions for the skyrmion RMS radius and energy, from which energy densities for large N may be estimated. The results indicate that for N>13 these densities reach twice the value for a single nucleon and for very large N they rise as N12/. Thus the skyrmion supports energy densities of sufficient magnitude to provide the conditions for the creation of a quark-gluon plasma at nucleon numbers low enough to achieve this condition with conventional nuclear projectiles and targets.