Regensburg 1998 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 21: Postersitzung III: Spin-Peierls-Systeme, Metall-Isolator-Übergang, Lokalisierung; SL: Theorie; Quantenflüssigkeiten und -kristalle; Amorphe Materialien, Tunnelsysteme; Borcarbide, Fullerene, konventionelle SL; SL dünner Filme; Experimentiertechniken

TT 21.39: Poster

Donnerstag, 26. März 1998, 15:00–18:30, D

Random transverse field Ising spin chain on fermionic space. — •Alexander Chudnovskiy — Institut f"ur Theoretische Physik, Universit"at W"urzburg, Am Hubland, 97074 W"urzburg

The fermionic Hilbert space of states is introduced on each site of the random transverse field Ising spin chain (RTFISC) model. In this way statistical charge fluctuations which are controlled by the chemical potential and temperature are introduced in addition to the spin fluctuations. The dependence of the spin-spin correlation length on the chemical potential at zero and small nonzero temperature is analysed in detail. Finite chemical potential results in the appearance of the quantum critical region in the phase diagram of the chain where the spin-spin correlations are quenched by charge fluctuations. At broad initial distributions of the couplings in the chain the dependences of the spin-spin correlation length on the distance from the critical point and on temperature become nonmonotonous. The results on the one-fermionic density of states are presented. At half filling it exhibits a crossover from the singularity close to the critical point (in the weakly-disordered and weakly ordered phases) to the soft-gap behavior far from the critical point (in the strongly disordered and strongly ordered phases).