Shell Effects in the First Sound Velocity of an Ultracold Fermi Gas.pdfVIP

Journal of Low Temperature Physics manuscript No. (will be inserted by the editor) 7 0 Luca Salasnich1 and Flavio Toigo2 0 2 Shell Effects in the First Sound Velocity of an g u Ultracold Fermi Gas A 0 3 ] h c February 1, 2008 e m - Keywords Degenerate Fermi gases, first sound, low-dimensional systems t Abstract We investigate the first sound of a normal dilute and ultracold two- a t component Fermi gas in a harmonic microtube, i.e. a cylinder with harmonic s . transverse radial confinement in the length-scale of microns. We show that the t velocity of the sound that propagates along the axial direction strongly depends a m on the dimensionality of the system. In particular, we predict that the first-sound - velocity display shell effects: by increasing the density, that is by inducing the d crossover from one-dimension to three-dimensions, the first-sound velocity shows n jumps in correspondence with the filling of harmonic modes. T he experimental o achievability of these effects is discussed by considering 40K atoms. c PACS numbers: 03.75.Ss, 67.40.Mj, 68.65.-k [ 1 v 1 Introduction 4 2 1 Macroscopic effects of quantum statistics are observable at ultra-low temperatures 4 with bosonic vapors of alkali-metal atoms 1,2. In the last years quantum degener- . acy has been achieved also with fermionic atoms 3,4,5,6,7 . It is important to observe 8 that the role of dimensionality in these degenerate gases has been experimentally 0 8,9,10 7 studied until now only with bosons . For fermions, it has been predicted that 0 a reduced dimensionality strongly modifies density profiles 11,12,13,14, collect