Orbital Momentum of Quasiparticles in Solids: Experimental Aspects

Several experiments on the orbital angular momentum of electrons have been reported in recent years. Among them, a phenomenon that has attracted significant attention is the Orbital Hall Effect(OHE), which generates the transverse flow of orbital angular momentum in response to an external electric field. Recent experiments have explored OHE through both optical and electrical approaches. Magneto-optical Kerr effect (MOKE) microscopy detects orbital polarization in light metals such as Ti, Cr, and V, confirming that orbital angular momentum can be probed directly. Electrically, OHE generates orbital torque in FM/NM bilayers, with intrinsic orbital Hall conductivity predicted to exceed spin Hall conductivity by over an order of magnitude. Orbital torque has enabled efficient magnetization switching with reduced current and power, positioning OHE as a promising driver of CMOS-compatible spintronics.