First topological insulator Floquet of integrated circuit. The arrows show how the transistors are used to achieve non-reciprocity. Credit: Aravind Nagulu

Some materials, such as wood, are insulators that block the flow of electricity. Conductors, like copper, allow electricity to flow through them. Other materials – semiconductors – can be either / or depending on conditions such as applied electric field or temperature. However, unlike wood, copper or silicon, topological insulators (TIs) are an exotic state of matter that is conductive on the surface but not in bulk. Such unique properties of the material are of great scientific importance and can be useful in a number of technologies, including wireless communications, radar and quantum information processing.

Through the combined efforts of the research laboratories of Aravind Nagulu, an assistant professor at Preston M. Green’s Department of Electrical Engineering and Systems Engineering at the University of Washington in St. Louis, and colleagues at Columbia University and the Center for Advanced Research at New York City University, the first topological insulator on integrated chip.

The results of the joint project were published on May 2 in the journal Natural electronics.

“Topological insulators have very interesting properties and are useful in themselves. However, their real potential is manifested when combined with non-reciprocal properties,” Nagulu said.

Non-reciprocity provides one-way propagation to electromagnetic (EM) waves. This feature can be used in full duplex communication, a method that allows data to be transmitted and received using the same frequency at the same time in an efficient manner, thus doubling the spectral capacity. In addition, TIs with non-reciprocal properties prevent the decay of the signal strength due to backscattering if the wave comes into contact with deformations or irregularities in the medium.

The team was able to use precisely designed time modulation of transistor switches to achieve non-reciprocity and topological insulation properties of standard semiconductor ICs without the need for exotic materials or extreme conditions.

This small integrated chip combines exotic areas of TI with real-world applications. It can also redirect EM waves on demand by reconfiguring individual single cells in the grid, creating a tissue that flexibly and randomly directs EM waves. The team demonstrates how a reconfigurable integrated circuit can be used for emerging 5G wireless applications such as multi-antenna full-duplex wireless communications and multi-antenna pulse radar.

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More information:
Aravind Nagulu et al, Floquet topological isolators with chip for 5G wireless systems, Natural electronics (2022). DOI: 10.1038 / s41928-022-00751-9

Provided by the University of Washington at St. Louis

Quote: New technology could double spectral bandwidth in some 5G systems (2022, May 11), extracted on May 11, 2022 from

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