Fig. 3.
Time-resolved investigation of polarization in magnetic field. a, b Time-resolved PL of σ+-output and σ−-output pumped by a σ+-polarized pulsed laser in Faraday geometry at Bz = 0 T (a) and Bz = −3 T (b). c, d Degree of polarization extracted from σ+ excitation PL at Bz = 0 T (c) and Bz = −3 T (d). e, f Valley polarization calculated from σ+ excitation and σ−-excitation PL. The σ− excitation PL data is in the Supplementary Figs. 1 and 2. At Bz = 0 T, the degree of polarization disappears quickly and hardly seen after 50 ns and valley polarization has a decay time of 15 ± 0.3 ns. At Bz = −3 T, the difference between σ+ output and σ− output is clearly seen even at 200 ns. The valley polarization at Bz = −3 T has a decay time of 1.745 ± 0.007 μs