Heat Usually Spreads. Scientists Just Made It Travel in Rays at Room Temperature

Heat inside a chip normally behaves like spilled water: it spreads outward, becomes harder to control and eventually limits performance. A UCLA-led team has now shown something very different. In a crystal called boron arsenide, heat-carrying vibrations moved along sharply defined paths at room temperature.

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The focused behaviour persisted for at least 1 micrometre, a distance relevant to many microscopic device features.

Why this result is unusual

In ordinary solids at everyday temperatures, atomic vibrations collide so often that heat spreads in a diffuse pattern. At very low temperatures, however, those vibrations can retain enough direction to form concentrated paths, an effect called phonon focusing.

The new work, published in Nature Physics on July 23, 2026, brings that behaviour into a far more practical temperature range. The researchers used nanoscale temperature mapping to compare conventional materials with boron arsenide. Ordinary samples produced circular heat patterns, while the boron arsenide crystal produced visible rays.

The crystal acts like a map for heat

Heat in a solid is carried partly by collective atomic vibrations known as phonons. These are not tiny particles flying through empty space; they are a useful quantum description of energy moving through a lattice of atoms.

Boron arsenide is unusually good at letting some phonons travel before scattering. Its crystal structure also favours particular directions. When the team changed the orientation of the crystal surface, the observed patterns changed predictably, producing fourfold, sixfold or eightfold arrangements. Calculations based on the material's atomic properties reproduced those patterns.

A helpful comparison is an optical fibre. A fibre guides light along a chosen route. The researchers are not claiming an equally mature heat cable, but their measurements suggest that a crystal could guide thermal energy instead of allowing it to spread everywhere.

Why chip designers may care

Modern processors pack more computing into smaller areas. Heat can reduce speed, shorten component life and force data centres to spend substantial energy on cooling. Most thermal engineering begins after the heat has spread, using heat sinks, liquid loops or airflow to move it away.

If materials can steer heat at its source, designers might one day route it around sensitive components or toward a collector. The concept could matter for AI accelerators, photonic hardware, aerospace electronics and quantum sensors, where small hot spots can become major constraints.

That promise should be read as a direction for engineering, not a finished product. Boron arsenide is difficult to grow at large scale, and real chips contain interfaces, defects and complex geometries that can disrupt ideal behaviour.

What happens next

Researchers can now test how the effect survives in thinner layers, patterned structures and interfaces with standard semiconductor materials. They can also investigate whether crystal orientation can be used deliberately to redirect hot spots inside working devices.

The discovery does not make fans or heat sinks obsolete. Its importance is more fundamental: at room temperature, heat does not always have to spread helplessly. Under the right conditions, matter itself can give it a route.