Solitons | UMQT

Tunable optical lattices for the creation of matter-wave lattice solitons

Sat, 10 Jan 2026 00:00:00 +0000

Lattice solitons of matter waves.

Thu, 16 Oct 2025 00:00:00 +0000

Floquet solitons of matter waves

Sun, 01 Aug 2021 00:00:00 +0000

Abstract

We experimentally study the dynamics of a weakly interacting Bose-Einstein condensate of cesium atoms in a 1D optical lattice with a periodic driving force. After a sudden start of the driving we observe the formation of stable wave packets at the center of the fi rst Brillouin zone (BZ) in momentum space, and we interpret these as Floquet solitons in periodically driven systems. The wave packets become unstable when we add a trapping potential along the lattice direction leading to a redistribution of atoms within the BZ. The concept of a negative effective mass and the resulting changes to the interaction strength and effective trapping potential are used to explain the stability and the time evolution of the wave packets. We expect that similar states of matter waves exist for discrete breathers and other types of lattice solitons in periodically driven systems. [Phys. Rev. Lett. 127, 243603 (2021)].

Floquet solitons of matter waves

Sun, 01 Aug 2021 00:00:00 +0000

Abstract

The concept of a negative effective mass and the resulting changes to the interaction strength and effective trapping potential are used to explain the stability and the time evolution of the wave packets. We expect that similar states of matter waves exist for discrete breathers and other types of lattice solitons in periodically driven systems. Phys. Rev. Lett. 127, 243603 (2021).

We further demonstrated non-destructive readout using state-selective imaging on the stretched state transition to enable post-selection for loss and avoiding the requirement to reload the arrays after every sequence.

For more details see our publication arXiv:2301.10510 (2023)."

Examples for markdown

Headline 2

Headline 3

Make this text italic

Make this text bold

Make a list
of a few items

~~Strike through this text.~~

Create a block quote reference.

not sure what this does

This is a link markdown examples

This is an image in images folder of page

This is the same image with title and caption. (The syntax with {{}} is called a shortcode)

This is a title

This is a caption

Same syntax can be used for up to 3 images with shortcode “figures”

This is a title

This is a caption

This is a title

This is a caption

This is a title

This is a caption

Good internal reference of author Dr. A. La Rooij

Option	Description
data	You can use this syntax to create a table.
engine	This is already extreme markdowning

Matter waves with position-dependent interactions

Wed, 28 Oct 2020 00:00:00 +0000

Motivation

Atoms can show attractive or repulsive interactions when they collide. But can atoms be both attractive and repulsive at the same time, e.g. attractive on the left side and repulsive on the right side?

The answer is: yes they can. The wave function of an ultracold atoms can be very large, extending over 100s of micrometers. We are used to the fact that the wave function adapts locally to a varying potential energy over this distance. Surprisingly, the same is true for its scattering properties, which can also vary locally over the extend of the wave function. The concept of an atom with locally changing interactions is only counterintuitive when we think of atoms as point like objects that crash into each other. A description using matter waves with fluid-like properties is well-suited to analyze those so called ‘‘collisionally inhomogeneous’’ systems.

Project summary

Collisionally inhomogeneous fluids exhibit spatially varying interactions between their particles. They frequently occur at interfaces, where interaction properties change due to a variation of an external potential or due to a change of the fluid’s composition. Examples for fluids at interfaces with a collisional inhomogeneity are liquid-vapour surfaces, and material junctions in condensed-matter physics.

We studied the evolution of matter waves for the simplest case, i.e. a spatial gradient of the interaction strength. Starting with a Bose-Einstein condensate with weak repulsive interactions in quasi-one-dimensional geometry, we monitored the evolution of a matter wave that simultaneously extends into spatial regions with attractive and repulsive interactions. We observed the formation and the decay of soliton-like density peaks, counter-propagating self-interfering wave packets, and the creation of cascades of solitons.

The matter-wave dynamics was well reproduced in numerical simulations based on the non-polynomial Schroedinger equation with three-body loss, allowing us to better understand the underlying behavior based on a wavelet transformation [Phys. Rev. Lett. 125, 183602 (2020)].

Breathing and higher-order excitations of solitons

Tue, 10 Sep 2019 00:00:00 +0000

Motivation

Bright matter-wave solitons are small dispersionless wave packets that keep its shape while propagating. Typically, this shape-preserving propagation is the result of a delicate balance between attractive interaction energy and dispersive kinetic energy. (Have a look at our project with Floquet solitons for bright matter-wave solitons with repulsive interactions.) The balancing condition relates parameters of the soliton, such as size, atom number, and interaction strength. It is easy to destroy this balance by changing the soliton size. For example, making the soliton larger decreases the kinetic energy while making the soliton smaller increases it.

What happens if we change the size of the soliton, e.g. make it slightly too large? Does the soliton return to its favorite size or does it fall apart?

The answer is: both. The soliton starts to oscillate for small size changes - getting periodically larger and smaller. Its oscillation frequency is a bit unusual, because there is no trap or external potential that could set it. Instead, the frequency is a property just of the soliton, depending on parameters such as atom number, interaction strength, and size.

There are two more options for the soliton to react when its size is far too large: (1) The soliton can shed atoms to get smaller. For example, when it is too large, it can eject atoms until it regains an atom number that fits to its larger size. (2) The soliton starts to oscillate but with a strange breathing-like motion, creating multiple sub-peaks during the oscillation (see cover image at the top of the page). Those oscillations are called higher-order oscillations and appear only for very specific sizes and with discrete frequencies.

Project summary

We experimentally studied the excitation modes of bright matter-wave solitons in a quasi-one-dimensional geometry. The solitons were created by quenching the interactions of a Bose-Einstein condensate of cesium atoms from repulsive to attractive in combination with a rapid reduction of the longitudinal confinement. A deliberate mismatch of quench parameters allowed us to excite breathing modes of the emerging soliton and to determine its breathing frequency as a function of atom number and confinement. In addition, we observed signatures of higher-order solitons and the splitting of the wave packet after the quench [Phys. Rev. Lett. 123, 123602 (2019)].