arXiv subjects

M. Havlicek

Publications and source records attributed to M. Havlicek.

5 recordsLinked to original sources

arXiv2012

Indirect Exchange Interaction in Fully Metal-Semiconductor Separated SWCNTs Revealed by ESR

The ESR response from highly metal-semiconductor(M-SC) separated SWCNTs for temperatures T between 0.39 and 200 K is characteristically different for the two systems. The signal originates from defect spins but interaction with free electrons leads to a larger line width for M tubes. The latter decreases with increasing T whereas it increases with T for SC tubes. The spins undergo a ferromagnetic phase transition below around 10 K. Indirect exchange is suggested to be responsible for the spin-spin interaction, supported by RKKY interaction in the case of M tubes. For SC tubes spin-lattice relaxation via an Orbach process is suggested to determine the line width.

cond-mat.mtrl-sci↗

arXiv2010

Spin Dependent Joule Heating due to Rashba Coupling and Zitterbewegung

Investigating microwave absorption in asymmetric Si quantum wells in an external magnetic field, we discover a spin dependent component of Joule heating at spin resonance. We explain this effect in terms of Rashba spin-orbit coupling which results in a current induced spin precession and Zitterbewegung. Evidence is based on the observation of a specific dependence of the electron spin resonance line shape and its amplitude on the experimental geometry which in some range suggests a "negative" differential power absorption.

cond-mat.mtrl-sci↗

arXiv2004

The fine gradings of sl(3,C) and their symmetries

We describe the normalizers for all non-conjugate maximal Abelian subgroups of diagonalizable automorphisms of sl(3,C) and show their relation to the symmetries of equations related to the graded contraction.

math-ph↗

arXiv2001

Representations of the q-deformed algebra U'_q(so_4)

We study the nonstandard $q$-deformation $U'_q({\rm so}_4)$ of the universal enveloping algebra $U({\rm so}_4)$ obtained by deforming the defining relations for skew-symmetric generators of $U({\rm so}_4)$. This algebra is used in quantum gravity and algebraic topology. We construct a homomorphism $ϕ$ of $U'_q({\rm so}_4)$ to the certain nontrivial extension of the Drinfeld--Jimbo quantum algebra $U_q({\rm sl}_2)^{\otimes 2}$ and show that this homomorphism is an isomorphism. By using this homomorphism we construct irreducible finite dimensional representations of the classical type and of the nonclassical type for the algebra $U'_q({\rm so}_4)$. It is proved that for $q$ not a root of unity each irreducible finite dimensional representation of $U'_q({\rm so}_4)$ is equivalent to one of these representations. We prove that every finite dimensional representation of $U'_q({\rm so}_4)$ for $q$ not a root of unity is completely reducible. It is shown how to construct (by using the homomorphism $ϕ$) tensor products of irreducible representations of $U'_q({\rm so}_4)$. (Note that no Hopf algebra structure is known for $U'_q({\rm so}_4)$.) These tensor products are decomposed into irreducible constituents.

math.QA↗

arXiv1999

Central elements of the algebras $U'_q({\rm so}_m)$ and $U_q({\rm iso}_m)$

The aim of this paper is to give a set of central elements of the algebras $U'_q({\rm so}_m)$ and $U_q({\rm iso}_m)$ when q is a root of unity. They are surprisingly arise from a single polynomial Casimir element of the algebra $U'_q({\rm so}_3)$. It is conjectured that the Casimir elements of these algebras under any values of q (not only for q a root of unity) and the central elements for q a root of unity derived in this paper generate the centers of $U'_q({\rm so}_m)$ and $U_q({\rm iso}_m)$ when q is a root of unity.

math.QA↗