Berlin 2005 – scientific programme

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Q: Quantenoptik und Photonik

Q 45: Quanteneffekte III

Q 45.5: Talk

Tuesday, March 8, 2005, 15:30–15:45, HU 1072

Bloch oscillations of Fermi and Bose atoms in optical lattices — •Alexey Ponomarev¹, Andrey Kolovsky^1,2 und Andreas Buchleitner¹ — ¹Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, D-01187 Dresden — ²Kirensky Institute of Physics, Ru-660036 Krasnoyarsk

Using the formalism of the Bose-Hubbard model, we compare the Bloch dynamics of bosonic and fermionic atoms. For a weak static force, Bloch oscillations (BO) of bosonic atoms are shown to decay within approx. one Bloch period. This effect finds its explanation in the properties of the Floquet-Bloch operator (i.e., the system evolution operator over one Bloch period), the matrix representation of which is found to be a random matrix of the circular orthogonal ensemble. In contrast to the bosonic dynamics, BO of spin-polarized fermionic atoms do not decay for arbitrarily weak static forcing. However, in a non-polarized Fermi gas (with two different spin projections), the BO decay once again, and the Floquet-Bloch operator pertains to the circular unitary ensemble. The case of strong static forcing, inducing quasiperiodic BO, will also be discussed.