Rashba and Dresselhaus Couplings in Halide Perovskites: Accomplishments and Opportunities for Spintronics and Spin–Orbitronics

Abstract

In halide hybrid organic-inorganic perovskites (HOP), spin-orbit coupling (SOC) presents a well-documented large influence on band structure. However, SOC may also present more exotic effects, such as Rashba and Dresselhaus couplings. In this perspective, we start by recalling the main features of this effect and what makes HOP materials ideal candidates for the generation and tuning of spin-states. Then, we detail the main spectroscopy techniques able to characterize these effects and their application to HOP. Finally, we discuss potential applications in spintronics and in spin-orbitronics in those non-magnetic systems, that would complete the skill set of HOP and perpetuate its ride on the crest of the wave of popularity started with optoelectronics and photovoltaics. Graphical TOC EntryPage 2 of 29 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d m a n u s c r i p tThe continuous success of halide hybrid organic-inorganic perovskites (HOP) as solar cell active materials follows several paths. The main activity after 2012 consisted in the search for improvement of the power conversion efficiency (PCE) in typical laboratory configuration (small area, controlled environment). It led to an unprecedented growth of the PCE that has repeatedly reached record values over 22%. 1,2 Meanwhile, another branch of HOP studies have been focused on improving the stability of those cells unfortunately sensitive to light and moisture. 3,4 Opting for various mixtures of halide and cations, 2 various forms, e.g. layered HOP, [5][6][7] or by encapsulating the materials, the stability went from few hours to several thousands hours. Encouraged by these breakthroughs, a third path has pushed the area of hight performance solar cells from less than 1 cm 2 up to 50 cm 2 with a PCE of 12.6%, 8 bringing the perovskite solar cells even closer to commercial use.A common point to all these record HOP materials is the presence of lead. Even though a large effort has been and still is dedicated to the search for efficient lead-free HOP materials, 9,10 their current record PCE remains around 6.4%. 11 It is certainly unfortunate for solar cells because of the known toxicity of lead, 12 even though solutions have early been proposed, 13,14 however, due to the large spin-orbit coupling (SOC) exhibited by Pb, it represents a great opportunity for optoelectronics, spintronics and spin-orbitronics applications where undesired heavy elements can find a place (e.g. arsenic, cadmium).The first identified effect of SOC in HOP materials has been a surprising giant splitting of conduction bands, 15,16 instead of the usual valence band splitting observed in classical semiconductors. 17 It has a strong influence on the band gap energy as well as on the effective masses and the oscillator strength of the optical transitions at the band gap. The chan...

Observation of long spin lifetime in MAPbBr3 single crystals at room temperature

“…However, at the surface or interface this inversion symmetry is necessarily broken and therefore allows for the formation of a surface Rashba state. Indeed, it has been proposed that the giant Rashba splitting previously observed in MAPbBr3 stems from this surface state and not the bulk [27,65,66] and recently experimentally proven in the MAPbrBr3 polycrystalline thin film [62]. It is thus tremendously advantageous to utilize single crystals in the analysis of the surface Rashba state, where a single material surface may be isolated and probed and the effects of defects such as grain boundaries is minimized.…”

“…We are unaware of any other reports on the spin lifetime in MAPbBr 3 single crystals at room temperature with which we could compare our experimentally obtained value of τ sf =189 ps. However, there have been some reports on polycrystalline MAPbBr 3 thin films measured at low temperature as well as several recent theoretical studies on MAPbBr 3 and MAPbI 3 single crystals [27,65,66,75,76]. Wang et al used partial circularly polarized photoluminescence (CPL) to measure spin lifetime via the optical Hanle effect in MAPbBr 3 thin films at low temperature, with measured relaxation times of τ sf =240 ps at 77 K that reduces by an order of magnitude at 110 K [76].…”

Spintronics of Hybrid Organic–Inorganic Perovskites: Miraculous Basis of Integrated Optoelectronic Devices

“…The field of HOP spintronics has only recently been established . Use of a new manipulable degree of freedom, based on the spin of an electron in combination with the spin of a photon based on strong spin‐orbit coupling (SOC), large‐scale Rashba and Dresselhaus splitting, triplet formation, a large Stark effect, the magneto‐optical effect, and polarized light‐related effects have all recently been discovered in HOPs.…”

“…[13] HOPs are thus promising candidate materials for use in traditional opto electronic devices, including photovol taic devices, [14][15][16] lightemitting diodes (LEDs), [17][18][19] and photodetectors, [20][21][22] with significant performance advantages.The field of HOP spintronics has only recently been established. [23,24] Use of a new manipulable degree of freedom, based on the spin of an electron in combination with the spin of a photon based on strong spinorbit coupling (SOC), [8,25] largescale Rashba and Dresselhaus splitting, [26] triplet forma tion, [27] a large Stark effect, [28] the magnetooptical effect, [29] and polarized lightrelated effects [30] have all recently been dis covered in HOPs. These great properties indicate that HOP spintronics is prospective for the next generation of integrated optoelectronic devices.…”

Ultrafast acoustic phonon scattering in CH3NH3PbI3 revealed by femtosecond four-wave mixing

“…As we show below, the Rashba effect strongly enhances the rate of acoustic phonon scattering. Since the magnitude of the Rashba effect in the valence band is expected to be weaker than in the conduction band due to the dominant contribution of the I 5p orbital to the valence states 53 , electron scattering is assumed to dominate the interband dephasing process. The magnitude of the Rashba coupling strength γ c was taken as an adjustable parameter to obtain the best fit to the experimental results.…”