Dynamics of reflection of ultracold atoms from a periodic one-dimensional magnetic lattice potential

We report on an experimental study of the dynamics of the reflection of ultracold atoms from a periodic one-dimensional magnetic lattice potential. The magnetic lattice potential of period $10\mu \text{m}$ is generated by applying a uniform bias magnetic field to a microfabricated periodic structure on a silicon wafer coated with a multilayered TbGdFeCo/Cr magneto-optical film. The effective thickness of the magnetic film is about 960 nm. A detailed study of the profile of the reflected atoms as a function of externally induced periodic corrugation in the potential is described. The effect of angle of incidence is investigated in detail. The experimental observations are supported by numerical simulations.

Figure 1

(Color online) Schematic showing an array of perpendicularly magnetized parallel slabs with period $a$. A one-dimensional magnetic lattice of elongated microtraps with nonzero potential minima is formed by applying bias fields along the $x$ and $y$ directions.

Figure 2

(Color online) Plots showing the partial derivatives of the magnetic field magnitude in the lattice potential (a) with respect to $y$ and (b) with respect to $z$. The parameters used in the calculations are given in the text.

Figure 3

(Color online) Periodic magnetic structure and current-carrying wires.

Figure 4

Absorption images showing experimentally observed spatial profiles of atoms reflected from a corrugated potential for different values of applied bias field $B_{by}$ (as indicated in the bottom right corner of each image) and hence different amplitudes of corrugation (for 9 ms time of flight). The horizontal and vertical directions correspond to the $y$ and $z$ axes, respectively. Gravity is in the downward direction, and the chip surface is above the top of each image.

Figure 5

(Color online) Angular spread of atoms as a function of applied bias field $B_{by}$. The minimum of the angular spread occurs at $B_{by}\simeq 2.2\text{G}$ rather than at $B_{by}=0\text{G}$ due the presence of a stray field.

Figure 6

(Color online) Calculated spatial profiles of the atoms as a function of corrugation. $B_{by}=\left(\text{a}\right)$ $-6.6$, (b) $-4.4$, (c) $-2.2$, (d) $-1$, (e) 0, (f) 1, (g) 2.2, (h) 4.4, and (i) 6.6 G.

Figure 7

(Color online) Series of absorption images showing the atomic density profile of reflected atoms for different values of $t_{\text{hold}}$. The time step in successive measurements is 4 ms. The horizontal and vertical directions correspond to the $y$ and $z$ axes, respectively.

Figure 8

(Color online) Calculated spatial profiles of the reflected atoms as a function of axial position and axial velocity.