Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 4: Quantenflüssigkeiten, Bose-Einstein Kondensate, ultrakalte Atome, ...

TT 4.5: Vortrag

Montag, 8. März 2004, 11:15–11:30, H19

Self-energy and critical temperature of weakly interacting bosons — •Peter Kopietz, Sascha Ledowski, and Nils Hasselmann — Institut für Theoretische Physik, Universität Frankfurt, Robert-Mayer-Str. 8, 60054 Frankfurt/Main

Using the exact renormalization group we calculate the momentum-dependent self-energy Σ ( k ) at zero frequency of weakly interacting bosons at the critical temperature T_c of Bose-Einstein condensation in dimensions 3 ≤ D < 4. We obtain the complete crossover function interpolating between the critical regime k ≪ k_c, where Σ ( k ) ∝ k^{2 − η}, and the short-wavelength regime k ≫ k_c, where Σ ( k ) ∝ k^{2 (D−3)} in D> 3 and Σ ( k ) ∝ ln(k/k_c) in D=3. From our Σ ( k ) we find for the interaction-induced shift of T_c in three dimensions Δ T_c / T_c ≈ 1.23   a n^1/3, where a is the s-wave scattering length and n is the density [1].

[1] S. Ledowski, N. Hasselmann, and P. Kopietz, cond-mat/0311043.