Münster 1999 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 22: Quantenstörstellen und quantenkritische Ph
änomene

TT 22.6: Vortrag

Freitag, 26. März 1999, 11:15–11:30, F3

Exact boundary critical exponents of integrable 1D quantum systems — •J. Voit¹, B. Brendel², and Y. Wang³ — ¹Universität Freiburg — ²Universität Würzburg — ³Universität Augsburg

We use the results from reflection Bethe Ansatz and boundary conformal field theory for the exact boundary critical exponents in integrable 1D quantum systems (e.g. the δ-function Bose gas, Heisenberg and Hubbard models) to calculate the effect of open boundaries on the single-particle spectrum. The boundary critical exponents are given in terms of the dressed charge (matrix) obtained from the Bethe Ansatz equations. It has the same form as in periodic systems. The effective low-energy theory is a “bounded Luttinger liquid”, and we prove that, while the boundary exponents are different from the bulk ones, when represented in terms of Luttinger parameters K_ρ,   K_σ, the implied values of K_ρ,   K_σ are the same as in the bulk. We calculate the single-particle spectral function and apply it to the photoemission properties of the organic superconductor (TMTSF)₂ PF₆, assuming that the surface has been damaged by cleaving and/or possibly is more 1D than the bulk. Using K_ρ-values suggested by others, we find the boundary spectral function ρ(ω) ∼ | ω|^α_b with α_b ∼ 1 … 3/2, in good agreement with experiment. Our suggestion could resolve the disagreement between photoemission and most other probes on the Luttinger liquid description of the Bechgaard salts.