Coherent Spin Dynamics of Electrons in Two-Dimensional (PEA)₂PbI₄ Perovskites

Abstract

The versatile potential of lead halide perovskites and two-dimensional materials is merged in the Ruddlesden− Popper perovskites having outstanding optical properties. Here, the coherent spin dynamics in Ruddlesden−Popper (PEA) 2 PbI 4 perovskites is investigated by picosecond pump−probe Kerr rotation in an external magnetic field. The Larmor spin precession of resident electrons with a spin dephasing time of 190 ps is identified. The longitudinal spin relaxation time in weak magnetic fields measured by the spin inertia method is as long as 25 μs. A significant anisotropy of the electron g-factor with the in-plane value of +2.45 and out-of-plane value of +2.05 is found. The exciton out-of-plane g-factor of +1.6 is measured by magnetoreflectivity. This work contributes to the understanding of the spindependent properties of two-dimensional perovskites and their spin dynamics.

Spin-Flip Raman Scattering on Electrons and Holes in Two-Dimensional (PEA)$_2$PbI$_4$ Perovskites

“…In the Voigt geometry the Raman shift of the electron E e line corresponds to |g e,(a,b) | = 2.50, see also Figure 3d. This value is in good agreement with g e,(a,b) = +2.45±0.05 measured by timeresolved Kerr rotation [47]. The slope of the linear fit to the double spin-flip E e+h Raman shift corresponds to |g e+h,(a,b) | = 1.98, see Figure 3e.…”

“…The details of their shifts are shown in Figures 3a,b,c. The E h line is only detected in high magnetic fields (see the black circles in Figure 3c) due to its small shift amounting to only −0.078 meV at uate |g e,c | = 2.11, agreeing well with g e,c = +2.05 ± 0.05 determined from time-resolved Kerr rotation on the same sample [47]. Identification of the hole and electron SFRS lines is done by comparing their g-factors with the universal dependence of the carrier g-factors on the band gap energy, that has recently been established for bulk lead halide perovskites [22].…”

“…The results are reported in Ref. 47. The dynamics trace reveals decays with times of 20 ps and 340 ps.…”

“…The electron g-factor anisotropy measured by TRKR in a vector magnet with smaller steps of the tilt angle can be found in Ref. [47]. It is interesting to note that the anisotropies of g e and g h almost compensate each other, so that their sum stays nearly isotropic, g e,c + g h,c = +1.98 and g e,(a,b) + g h,(a,b) = +1.99.…”

“…Most of the dynamical studies were carried out above liquid nitrogen up to room temperature, where the spin relaxation times do not exceed a few picoseconds. Recently, time-resolved Kerr rotation allowed measurements of the coherent dynamics of electron spins in the (PEA) 2 PbI 4 2D perovskite [47].…”