New synthetic '4D' metamaterial can control solid surface waves
Humans experience the world primarily in three dimensions. However, scientists have recently started investigating the prospects of a "fourth dimension" (4D), or synthetic dimension - our perspective beyond our physical world.
The University of Missouri scientists have developed a new form of metamaterial based on the method of a 4D synthetic dimension.
As per the official release, this material can control energy waves on the surface of a solid substance. These energy waves are known as mechanical surface waves, which could aid in determining how vibrations propagate through a solid surface material.
“Conventional materials are limited to only three dimensions with an X, Y, and Z axis,” said Guoliang Huang, co-author of this study from the university, in an official release.
“But now we are building materials in the synthetic dimension, or 4D, which allows us to manipulate the energy wave path to go exactly where we want it to go as it travels from one corner of a material to another,” explained Huang.
The primary benefit of this novel metamaterial is in the realm of quantum computing. Still, it may also have implications in creating safer engineering solutions for earthquake-prone areas.

Metamaterial based on the topology field of mathematics
This new metamaterial was developed using a field of mathematics known as topology. This branch is concerned with examining shapes and their arrangement in space.
This research used the topological pumping effect, which according to the study, “allows waves to navigate a sample undisturbed by disorders and defects.”
Topological pumping has the potential to enhance quantum mechanics and quantum computing by enabling the creation of higher-dimension quantum-mechanical phenomena.
The material might also be utilized to develop technical solutions for earthquake-resistant structures.
“Most of the energy — 90 percent — from an earthquake happens along the surface of the Earth. Therefore, by covering a pillow-like structure in this material and placing it on the Earth’s surface underneath a building, it could potentially help keep the structure from collapsing during an earthquake,” Huang.
The results were published in the journal Science Advances.
Study abstract:
Topological pumping allows waves to navigate a sample undisturbed by disorders and defects. We demonstrate this phenomenon with elastic surface waves by strategically patterning an elastic surface to create a synthetic dimension. The surface is decorated with arrays of resonating pillars that are connected by spatially slow-varying coupling bridges and support eigenmodes located below the sound cone. We establish a connection between the collective dynamics of the pillars and that of electrons in a magnetic field by developing a tight-binding model and a WKB (Wentzel-Kramers-Brillouin) analysis. This enables us to predict the topological pumping pattern, which we validate through numerical and experimental steering of waves from one edge to the other. Furthermore, we observe the immune nature of the topologically pumped surface waves to disorder and defects. The combination of surface patterning and WKB analysis provides a versatile platform for controlling surface waves and exploring topological matter in higher dimensions.