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Black holes on a chip

Black holes are known for their ability to trap everything, even light, behind an 鈥渆vent horizon鈥�. While real black holes are far beyond our experimental reach, physicists have theorized that similar horizon鈥憀ike effects can be recreated using waves in carefully engineered systems.

Gnoatto鈥檚 work explores whether spin waves can be used to build such analogue horizons. Because these waves respond strongly to the flow of spin鈥憄olarized electric currents, researchers can change their speed and direction, potentially creating the conditions needed for a 鈥渕agnonic black hole鈥�.

Steering spin waves with electric currents

A key mechanism in this research is spin鈥憈ransfer torque: when an electric current passes through a magnetic material, it becomes spin鈥憄olarized and can push on the magnetization. By shaping the current, such as by narrowing sections of the device, Gnoatto created current density gradients that influence how spin waves propagate.

These gradients are theoretically essential for forming analogue event horizons, where spin waves moving against the current slow down and could even become trapped, mimicking the physics near a black hole boundary.

Engineering materials for magnonic horizons

To make such devices viable, the underlying materials must exhibit strong spin polarization and low magnetic damping. Gnoatto studied thin鈥慺ilm ferromagnets and showed, for the first time, a systematic link between spin polarization and magnetic damping in CoFeB alloys, providing a new guideline for selecting materials suitable for spin鈥憌ave manipulation. He also optimized nanofabrication techniques, enabling the creation of more complex device geometries necessary for reliable analogue鈥慻ravity experiments.

Toward wave鈥慴ased computing: a magnonic multiplexer

Beyond analogue gravity, the same principles can be used for reconfigurable computing devices. Gnoatto designed and investigated a spin鈥憌ave multiplexer, which routes spin waves to different output channels depending on the applied current. This is an important step toward wave鈥慴ased computing, a field aiming to build information processors that use magnons instead of electrons, dramatically lowering energy consumption.

A bridge between cosmology and computation

Gnoatto鈥檚 work pioneers a new experimental platform where concepts from cosmology meet next鈥慻eneration computing. By demonstrating how electric currents can shape spin鈥憌ave behavior and showing the first experimental steps toward magnonic event horizons, his thesis lays the scientific foundation for both analogue鈥慻ravity studies and practical magnonic devices. His results highlight how fundamental physics can inspire new technologies, and how nanoscale materials engineering can bring those ideas to life.