Coupled exciton-trion spin dynamics in a MoSe ₂ monolayer

Abstract

Understanding and controlling the spin degree of freedom in two-dimensional transition metal dichalcogenides offers the potential for designing functional quantum materials. This work investigates the dynamics of photo- and resident carrier spins in an encapsulated MoSe2 monolayer using non-degenerate time-resolved Kerr-rotation microscopy. The lightly doped monolayer exhibits clear exciton and trion resonances with spin-polarizations that are characterized by a fast (~20 ps) decay attributed to photocarrier relaxation and recombination, followed by a slow (~690 ps) decay associated with resident carrier depolarization. Dual-frequency Kerr-rotation spectra directly reveal exciton-trion coupling on ultrashort timescales and within the spin coherence time of the system. Moreover, the distribution of the exciton-trion coupling features exposes inhomogeneous broadening likely arising from different domains within the excitation spot.

Robust Interlayer Exciton in WS2/MoSe2 van der Waals Heterostructure under High Pressure

“…Furthermore, the fast decay lifetime of 93 ps for the WS 2 /MoSe 2 heterostructure, obtained using a 750 nm long-pass filter, is significantly longer than the decay of individual WS 2 and MoSe 2 , which is attributed to the lifetime of interlayer exciton and is comparable with previously reported values . The slow decay component has a lifetime of ∼418, 604, and 774 ps for WS 2 , MoSe 2 , and the WS 2 /MoSe 2 heterostructure, respectively, which could be attributed to either different localization of the charge carriers or cooling off the lattice …”

“…For all areas, the PL decays are fit by a two-component exponential decay, namely, a fast decay τ 1 and a slow decay τ 2 . From the data shown in Figure F, we obtain a fast decay lifetime of 32 and 44 ps for WS 2 and MoSe 2 , respectively, which is similar to the transient absorption measurements of other monolayer TMD materials . The fast decay component is attributed to exciton recombination, which takes up a percentage of higher than 98% (Table S1), indicating that the radiative recombination channel of the A exciton is dominant.…”

Magnetic field control of light-induced spin accumulation in monolayer MoSe$_2$

“…We noticed that to properly reproduce our measurements, the radiative recombination rate could not be either the shorter nor the longer decay process, and instead, good results were achieved by using decay times (τ ) of tens of picoseconds. The latter agrees with previous reports of the trion lifetime for MoSe 2 [17,18,26,29]. Therefore, as our results point to a spin accumulation of holes at the long time range (τ v = 5 ns), the fast decay (τ c = 1.8 ps) is assigned to electron transfer at the conduction band.…”

Controllable Magnetic Proximity Effect and Charge Transfer in 2D Semiconductor and Double‐Layered Perovskite Manganese Oxide van der Waals Heterostructure

“…The valley degrees of freedom coupled with the spin degrees of freedom (spin-valley locking), which originate from strong spin-orbit interactions and the breaking of inversion symmetry, enable the selective photogeneration of excitons and trions at the K or −K valleys by shining circularly polarized light; this leads to the formation of valleypolarized excitons and trions (valley polarization) in monolayer MX 2 . [12][13][14][15][16] The optically generated excitons and trions are highly sensitive to the physical properties of substrate materials, owing to the proximity effect. [17][18][19] The monolayer MX 2 on the insulating ferromagnetic materials provides a platform for investigating the exchange interactions between the valley spin-polarized excitons (trions) and ferromagnetic spins via proximity magnetic-exchange effects, which leads to tunable valley spin polarization and large valley splitting.…”