Acta Physica Polonica A
Bose-Einstein Condensates in Optical Lattices
Wojciech Wasilewski, Marek Trippenbach, Kazimierz Rza̧żewski
Abstract
c h a and K. R z¨âew ski b a I nst i t ut e of E xp eri m ental P hysi cs, Opti cs D i vi sion W arsaw Uni versi ty , Hoâa 69, 00-681 W arsaw, Pol an d b Center for Theo reti cal Physi cs, Pol ish Aca dem y of Sciences al .Lo tni k §w 32/ 46, 02-668 W arsaw, Po l and W e st udy an ult ra cold dilute gas of bosonic ato ms in an optical lattice induced by intersecting laser b eams.A s a Ùrst appro ximation w e neglect conÙning p otential and atom {atom interactions.In t his case the Gross{ Pitae vs ki j equation reduces to simple Mathieu equation.U pon cho osing p erio dic boundary conditions this problem has well know n perio dic solution.T his simple picture allow s to demonstrate lo cali zation of the w ave packet and formation of the band structure.W e calcula te spectrum of the excited states as a function of the strength of mo dulati ng p otential and using a standard adiabatici ty criterion w e predict the most e£cient w ay to ramp up optical lattice , w ithout higher state excitation.Finall y, we discuss the in Ûuence of the atom{atom interaction (nonlinea rity ) on the adiabatic ity of the pro cess.