Ballistic transport of orbital current from chromium

The ballistic orbital current $({J}_{L})$ promises more efficient information transfer over longer distances in various materials compared with spin current $({J}_{S})$. However, experimental observation and quantitative investigation of ballistic orbital transport remain elusive due to the entanglement between ${J}_{L}$ and ${J}_{S}$. Here, we show that the vanishingly small spin-orbit coupling of Cu and its negligible $d$-orbital character close to the Fermi energy allow spin-independent orbital investigation. Combined with theoretical and experimental results, we reveal that the ballistic transport length of ${J}_{L}$ generated by Cr reaches up to 13 nm, a magnitude larger than the typical spin-diffusion length of 1--2 nm. Moreover, an orbital efficiency of 0.44 was quantitatively determined in Cr, which is 1.9 times larger than that of spin-dominated heavy metal Pt. These results not only provide a convenient approach for the quantitative study of ${J}_{L}$ but also highlight the significant potential of orbital engineering in spin-orbitronics applications.