Key takeaways Researchers have demonstrated that phonons, atomic heat-carrying vibrations with quantum properties, can travel in focused, ray-like paths at room temperature. The team demonstrated phonon focusing at room temperature in boron arsenide, a crystalline semiconductor material with high thermal conductivity. The team demonstrated phonon focusing at room temperature in boron arsenide, a crystalline semiconductor material with high thermal conductivity. “By enabling heat to be guided, focused and redistributed with nanoscale precision at room temperature, the discovery establishes a foundation for quantum thermal engineering.” At room temperature, phonons have typically been shown to scatter extensively and quickly lose their wave coherence, causing heat to spread diffusively.