Efficient electron spin relaxation by chiral phonons in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>WSe</mml:mi><mml:msub><mml:mrow/><mml:mn>2</mml:mn></mml:msub></mml:math> monolayers

In transition metal dichalcogenide semiconductor monolayers, the spin dynamics of electrons is usually controlled by the spin-valley locking effect: a carrier spin flip occurs only if there is a simultaneous change in the valley. However, very little is known about the intravalley spin relaxation processes. Here, the authors demonstrate that the spin relaxation of an electron in WSe${}_{2}$ monolayers can occur efficiently without a change in valley thanks to chiral phonons. The consequence is an efficient relaxation from bright to dark excitons.