Chip-scale Floquet topological insulators to enhance 5G wireless communications

Ingrid Fadelli is a writer for Phys.org.

Floquet topological insulators are materials with different phases that come from different times in the crystal structure. The materials feature unusual electron conduction properties. In recent years, there has been a lot of interest in using tailored metamaterials to explore similar features for electromagnetic waves, which could lead to exciting opportunities for a wide range of applications, including the development of wireless communication, radar and quantum technology.

Floquet topological insulators have been introduced by researchers at Columbia University, City University of New York, and the University of Texas at Austin. Their paper focuses on the class of materials that can guide light in unusual and beneficial ways.

Harish Krishnaswamy, one of the researchers who carried out the study, said that Prof. Alu and he have both been active in the area of time-modulated materials and circuits. Several fundamental limits associated with static materials or circuits can be broken by time-modulated materials or circuits. One can achieve non-reciprocity, where signals travel in different ways in forward and reverse directions, to build non-reciprocal components.

The idea of building a time-modulated, non-reciprocal circulator could be extended to the design of topological insulators by connecting many circulators in a lattice. Material scientists have explored this idea from a theoretical point of view, but it has never been shown in action. Building many time-modulated circulators in a robust and generalizable fashion is a challenging task, and so far these devices have a moderate bandwidth of operation. Krishnaswamy and his colleagues were able to integrate the time-modulated circulators on a Silicon chip and dramatically extend their bandwidth of operation.

Krishnaswamy said that integrated circuits are a powerful platform to build complex time-modulated circuits with many elements.

The researchers developed a chip that could be used to create full-duplex phased-array wireless technology, which combines two different 5G wireless capabilities: full-duplex and multi-antenna operation. The team demonstrated the feasibility of their chip in their paper.

The researchers involved in the study told TechXplore that the propagation of waves in their bulk is not allowed, but that they ensure efficient and robust wave propagation on their boundaries.

Over the past decade or so, researchers have developed different types of PTIs that rely on broken symmetries in space. The breaking of time symmetry is what the PTI chips rely on. The team and other research groups believed that this approach would ensure one-way propagation and prevent back reflections, which would make it a promising approach to attain more robust wave propagation on the boundaries of the devices.

The broken symmetry in time is obtained by changing the material properties temporally with tailored modulation patterns, which is the first of such class of PTIs.

The recent study carried out by this team of researchers could have significant implications for the development of wireless communication tools and other state-of-the-art technologies. The Floquet PTI chip they developed could soon be integrated and evaluated in various devices, as a result of the new form of wave propagation demonstrated in their study.

The unique features mentioned above are suited for enhancing communication systems, as we demonstrate in the paper in a couple of relevant applications.

More information: Aravind Nagulu et al, Chip-scale Floquet topological insulators for 5G wireless systems, Nature Electronics (2022). DOI: 10.1038/s41928-022-00751-9 Journal information: Nature Electronics

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