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TT: Fachverband Tiefe Temperaturen

TT 38: Correlated Electrons: Low-dimensional Systems - Models 1

TT 38.5: Vortrag

Donnerstag, 26. März 2009, 10:45–11:00, HSZ 301

Temperature dependent optical conductivity in frustrated chain cuprates near the ferromagnetic-spiral critical point — •Stefan-Ludwig Drechsler¹, Jiri Malek^1,2, Satoshi Nishimoto¹, Helge Rosner³, Ulrike Nitzsche¹, Roman Kuzian^1,4, and Helmut Eschrig¹ — ¹IFW-Dresden, Germany — ²Inst. Phys. ASCR, Czech Republic — ³MPI-CPfS Dresden, Germany — ⁴Inst. of Mat. Sci. Problems, Kiev, Ukraine

The optical conductivity σ(ω) [1] and the loss function of EELS are calculated at finite temperature T for CuO₂ chain clusters within a five-band O2pCu3d-Hubbard model using exact diagonalizations and the DMRG-technique. Data at T = 300 K for Li₂CuO₂ are reanalyzed within this approach. The relative weights of Zhang-Rice singlet and triplet charge excitations near 2.7 and 4 eV, respectively, depend strongly on T, and a rather dramatic dependence of σ(ω) on the ratio of the 1^st to 2^nd neighbor exchange integrals is predicted. From our results information about exchange interactions for frustrated edge-shared cuprates can be obtained from T-dependent optical spectra. The obtained exchange integrals compare well with results of LDA+U calculations. Our results are also relevant for magnetically weakly coupled unfrustrated wide-gap insulators in general.

[1] J. Málek et al., PRB 78 060508(R) (2008).