arXiv subjects

Alexander Seidel

Publications and source records attributed to Alexander Seidel.

58 records · Page 4Linked to original sources

arXiv2004

Flux period, spin gap, and pairing in the one-dimensional t-J-J'-model

Using the factorization of the wavefunction in the t-J-J'-model at small exchange couplings, we demonstrate the connection between the existence of a spin gap and an hc/2e flux periodicity of the ground state energy. We conjecture that all spin-gapped SU(2)-invariant Luttinger liquids have hc/2e flux periodicity, and that this is connected to the fact that a gapped spin-1/2 chain always breaks translational symmetry by doubling the unit cell.

cond-mat.str-el↗

arXiv2004

Lightly doped dimerized spin chain in the one-dimensional t-J-J' model

We study the one-dimensional t-J-J'-model in the limit of small hole doping $x$ and small $J/t$, $J'/t$. Special emphasis is put on the regime $J'/J \approx .5$ where a spin gap is present at small doping and the undoped spin chain is strongly dimerized. Using a perturbative approach and Luttinger liquid arguments, we demonstrate for this non-integrable class of models that the charge degrees of freedom behave as non-interacting spinless solitons in the dilute hole limit. Our approach is also used to evaluate the energy and mass renormalization of a single hole. Interestingly, the corrections of these quantities are in powers of $\sqrt{J/t}$. At $J'/J=.5$ we construct a variational spin-polaron wave function for the hole and find good agreement with our perturbative results.

cond-mat.str-el↗

arXiv2003

Doped dimerized spin chains: Another path to superconductivity

This paper has been withdrawn by the authors, since we have come to believe that the present approach is not convergent at small doping. We will shortly submit an improved theory of the tJJ' model at small J/t in the dilute hole limit. This will be a new submission will go by a different submission number.

cond-mat.str-el↗

arXiv2002

S=1/2 chains and spin-Peierls transition in TiOCl

We study TiOCl as an example of an S=1/2 layered Mott insulator. From our analysis of new susceptibility data, combined with LDA and LDA+U band structure calculations, we conclude that orbital ordering produces quasi-one-dimensional spin chains and that TiOCl is a new example of Heisenberg-chains which undergo a spin-Peierls transition. The energy scale is an order of magnitude larger than that of previously known examples. The effects of non-magnetic Sc impurities are explained using a model of broken finite chains.

cond-mat.str-el↗