Detection of the Orbital Hall Effect

I n the spin Hall effect, an applied electric field drives a current of electron spin in a direction transverse to the field. In a transitionmetal, theorists predict that an orbital angular momentum (OAM) current can also flow. Now two groups have independently observed this so-called orbital Hall effect (OHE) [1, 2]. These observations supplement onemade by a third group earlier this year [3]. Together these demonstrations constitute a step toward the development of “orbitronic” devices based on an electron’s orbital degree of freedom.