Fig. 1
From: The valley Zeeman effect in inter- and intra-valley trions in monolayer WSe2
Scheme of singlet and triplet trions in WSe2. Generalized dispersion relations E(k), where k is the wavevector of the excess electron, of the four optically bright ground state negative trions in monolayer WSe2, following the convention established in refs. 20,25,26. Side panels illustrate the spin-valley configurations of the constituent carriers of each trion variety. v1 is the topmost spin-subband within the valence band, while c1 (c2) is the lower (upper) energy spin-orbit split conduction band. Based on optical selection rules, the black electron (black filled circle) and hole (black empty circle) are the recombining pair, while the purple electron (purple filled circle) is excess and occupies band c1. Orange (green) conduction and valence band states are spin up (down). Red (blue) colours denote σ+ (σ−) helicity of the bright transition. The trion states are labelled XY where X = s, t for singlet or triplet, Y = +, − for σ+ or σ− emission helicity. Purple arrows indicate the intervalley Coulomb exchange interaction, present only in triplet trions, which raises the energy of the triplets by an amount δex above the singlets. This energy gap gives rise to the trion fine structure in emission
