Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session S41: Spin and Chiral Properties of Halide Perovskites |
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Sponsoring Units: DMP Chair: Ross Kerner, National Renewable Energy Laboratory; Juan-Pablo Correa-Baena Room: Room 319 |
Thursday, March 9, 2023 8:00AM - 8:12AM |
S41.00001: Numerical investigations on exciton spin relaxation mechanisms in colloidal CsPbBr3 perovskite nano-crystals. Indrajit P Wadgaonkar, Marco Battiato Lead halide perovskites are a promising candidate for opto-electronic functional devices owing to a unique fine structure splitting (FSS) of their exciton states, which results from an inherent spin-orbit coupling and shape anisotropy instead of strong quantum confinement. However, a deeper understanding of spin decoherence mechanisms in these materials is still lacking. Although empirical suggestions on spin relaxation by Elliot- Yafet (EY), D’yakonov-Perel’ (DP) or Maialle-Silva-Sham (MSS) mechanisms exist, importantly, an exact disentanglement of the regimes where each of these mechanisms dominate is missing. In this work we present results of our recent Monte Carlo simulations to unravel the experimentally observed, robust, coherent dynamics of exciton FSS states in colloidal caesium lead bromide perovskite nano-crystals. Using a careful fit of the experimentally measured evolution of the spin polarisation to the one obtained from the Monte Carlo simulations we conclude that the average spin precession frequency, which is proportional to the FSS energy splitting and hence the oscillatory spin dynamics, is dependent on the nano-crystal size but independent of the temperature. We also decode the experimentally observed anomalous temperature dependence of the spin decoherence and identify different temperature regimes where the individual spin relaxation mechanisms dominate. Our work provides a comprehensive understanding of the exciton spin decoherence in these materials and helps to build an unambiguous picture of the complex interplay between the underlying spin relaxation mechanisms. This would pave way for engineering robust high temperature opto-spintronics and quantum information devices. |
Thursday, March 9, 2023 8:12AM - 8:24AM |
S41.00002: Independent Spin and Charge Transport Measurements in Hybrid Organic-Inorganic Perovskites. Paul W Bailey, Zeev V Vardeny Hybrid organic-inorganic perovskites (HOIPs) are of interest because of their potential for spintronics applications. HOIPs have relatively high mobilities while also exhibiting spin-orbit coupling due to the presence of heavy atoms like lead and halogens. We study the spin and charge transport properties of HOIPs (namely CsPbBr3 and MAPbBr3) through independent measurements. We extract the spin coherence length using inverse spin Hall effect measurements in NiFe-HOIP-Pt trilayer devices. Separately, we extract the charge carrier mobility using the time-of-flight method on HOIP single crystals. By using independent measurements, we can test whether spin transport and charge transport are mediated through the same or different processes. |
Thursday, March 9, 2023 8:24AM - 8:36AM |
S41.00003: The Landé g-factor of electrons in 2D-PEPI studied by transient photoinduced quantum beatings Rikard J Bodin, Uyen Huynh, Jeffrey L Blackburn, Valy Z Vardeny A new class of materials known as hybrid organic-inorganic perovskites (HOIP) has drawn interest for its optoelectronic properties and potential for use in new devices such as solar cells. (C6H5C2H4NH3)2[PbI4] (or PEPI) is a 2D-HOIP that has shown a variety of exotic optoelectronic properties, such as Rashba splitting. We have studied the Landé g-factor of electrons in pristine and doped PEPI films by the technique of photoinduced transient quantum beatings in the ps time domain. The PEPI films were prepared and doped in a Benzyl Viologen solution for differing lengths of time to control the degree of doping. Electronic doping was verified by doping-induced absorption spectroscopy in the mid-IR spectral range. We observed an oscillatory time-resolved response of which frequency changed with the applied magnetic field in the Voight configuration, from which the g-value could be determined. We found that the electron g-factor for the undoped PEPI is higher than that of highly doped PEPI films. |
Thursday, March 9, 2023 8:36AM - 8:48AM |
S41.00004: Ionic and electronic current under photo-illumination in a chiral organic metal halide hybrid Zhenqi Hua, Azza Ben-Akacha, Gabriel Gavet, Darian Discenza, Zihan Zhang, Hanwei Gao, Biwu Ma, Peng Xiong Organic halide perovskites have attracted much interest due to their favorable properties in optoelectronics. We recently demonstrated that single crystals of the 1D organic metal halide (R-α-MBA)PbI3 exhibit excellent chemical and electronic stability, which enabled highly reproducible time-dependent electrical measurements[1]. The four-terminal I-V and V-t measurements yielded real-time ionic and electronic currents and revealed single exponential intrinsic ion migration dynamics of distinct time constants as short as 3 s. Here, we report the effects of photo illumination of different wavelengths and intensities on the ion migration dynamics. The reproducible I-V and V-t results evidence reversible effects of photo illumination: Both the magnitude of the ionic current and the time constant of the exponential ion migration dynamic increase with the illumination time and intensity, which indicate an increase of mobile ion density and decrease of their mobility with light illumination. The stability of the materials and reversibility of the photo-activated and field-assisted ion migration suggests that the shift current may be measured in the chiral crystals using scanning photo-current microscopy. A comparison of the shift current in crystals of opposite handedness (R- vs S-) may produce new insight into its microscopic origin. |
Thursday, March 9, 2023 8:48AM - 9:00AM |
S41.00005: Ferroelectric Rashba cofunctionality in [CH3PH3]SnBr3 RAVI KASHIKAR Ferroelectric materials exhibit spontaneous polarization, which is reversible by the application external electric field. A few ferroelectrics exhibit spin splitting due to spin-orbit coupling, with values ranging from 0.1 meV to 4 eV. Such spin-splitting gives origin to spin-textures, which in ferroelectrics may couple to the direction of electric polarization giving origin to ferroelectricity Rashba effects co-functionality, which is of great importance for potential applications. We use first-principles density functional theory computations to predict Rashba effects cofunctional with ferroelectricity in a recently synthesized lead-free hybrid organic-inorganic perovskite MPSnBr3 (MP = methylphosphonium, ( [CH3PH3] +)). The ground state of the material is polar monoclinic with calculated spontaneous polarization of 3.01 µC/cm2. It exhibits near band edges spin-splitting of up to 3.3 meV and Rashba coefficient up to 0.62 eV Å. The spin textures have different topologies in the conduction and valence bands, which originates from the difference in the spin-momentum coupling strengths. Our study reveals the potential of MPSnBr3 for low-temperature applications in spintronics and quantum computing. |
Thursday, March 9, 2023 9:00AM - 9:12AM |
S41.00006: Investigation of shift current along off-polar axis in organic-inorganic perovskites Taishi Noma, Fumito Araoka, Daigo Miyajima Shift current has attracted much attention for photovoltaic applications because it is energetically less dissipative (npj Comput. Mater., 2, 16026, 2016). Shift current is generated by the shift of electron clouds in real space upon photoexcitation, and it is expected to flow in any noncentrosymmetic materials belonging to piezoelectric point groups. However, the correlation between shift current and polarization is still under debate. Recent experimental results showed that the shift current of organic-inorganic hybrid perovskites is generated dominantly along the polarization axis (Chem. Mater., 34, 10, 4428, 2022). In this work, we investigate the shift current of organic-inorganic perovskites flowing along off-polar axis. We synthesized ((R)-(-)-1-cyclohexylethylamine)8Pb3I14 single crystals belonging to a chiral-polar space group of P21. We measured the zero-bias photocurrent flowing along the direction perpendicular to the polarization axis. It was found that the photocurrent generation along the off-polar axis can be well explained by the shift current theory and cannot be explained by the classical bulk photovoltaic effect where internal electric fields make a great contribution to photocurrent generation. In future work, the contribution of exciton and interband transitions will be elucidated by spectroscopic measurement. |
Thursday, March 9, 2023 9:12AM - 9:24AM |
S41.00007: Large Optical Anisotropy Factors of a Chiral Bismuth Iodide Hybrid Organic-Inorganic Semiconductor Alan J Phillips, Liang Yan, Yi Xie, Matthew Hautzinger, Heshan S Hewa Walpitage, Peter C Sercel, David B Mitzi, Zeev V Vardeny, Wei You, Jeffrey L Blackburn Chiral materials are important tools for interconverting the spin angular momentum of circularly polarized light with electronic spin to help realize a wide variety of emerging spin-based technologies. Here we demonstrate that thin films of a Bismuth-based chiral 0D hybrid organic-inorganic semiconductor (HOIS) exhibit large anisotropy values for circularly polarized light emission (CPLE) that approach 50% circular polarization. The observed anisotropy is strongly correlated with the crystallographic orientation of the thin film and is also strongly temperature-dependent, with a marked anti-correlation with exciton transition linewidth. Detailed analysis of the CPLE anisotropy indicates large contributions from structure-dependent scattering that are analogous to the LDLB effect observed for circular dichroism, caused by the linear dichroism and linear birefringence. Although this effect has been observed for organic thin-films, this first demonstration in a HOIS system provides a unique route for enhancing carrier spin polarization and polarization-dependent emission in hybrid semiconductors. These results provide a fundamental framework for understanding and harnessing the properties of low dimensional and low symmetry chiral HOIS materials for circularly polarized light applications. |
Thursday, March 9, 2023 9:24AM - 9:36AM |
S41.00008: Correlation between band gap shifts due to symmetry breaking and spin-orbital coupling in halide perovskites Fernando P Sabino, Xingang Zhao, Gustavo M Dalpian, Alex Zunger The calculation of band gaps of Halide perovskites (HP) differs from analogous calculations of more conventional semiconductors in that two additional factors need to be considered: (i) creation of a structural polymorphous network (a distribution of octahedral titling for different octahedra in cubic structures) – which increase the band gaps and (ii) spin-orbital coupling (SOC) – generally reducing the band gaps for compounds with high Z atoms. This raises the question to what extent effects (i) and (ii) compensate each other or if they are correlated in some way. We addressed this question by a series of DFT band structure calculations on cubic ABX3 compounds where effects (i) and (ii) are both included; or both excluded, or including one at the time. For the most studied inorganic halide perovskites, the SOC - induced band gap reduction has a low correlation with the band gap increase due to polymorphous network formation. The accuracy of treating the gap shifts due to (i) and (ii) as independent corrections for nominal cubic Pm-3m structures will be presented and discussed. |
Thursday, March 9, 2023 9:36AM - 9:48AM |
S41.00009: First-principles structure prediction and chirality transfer in chiral organic-inorganic perovskite nanoplatelets RUYI SONG, Qinxuan Cao, Christopher Chan, Zhiyu Wang, Pui Yang Wong, Kam Sing Wong, Haipeng Lu, Volker Blum Hybrid metal halide perovskites are innovative optoelectronic materials with outstanding quantum yields and are potential hosts of spin-splitting for spin-selective transport, photoluminescence, and spin-orbitronics. Structure-based chirality transfer from organic to inorganic components has been observed in bulk 2D hybrid organic-inorganic perovskites (2D HOIPs). Using a first-principles approach, we here elucidate the structure and spin nature of perovskite nanoplatelets with surface chiral ligands (R-/S-β-methylphenethylamine). We conduct a systematic geometry search and a series of DFT-based high-throughput structure relaxations, trying to enumerate the likely organic-inorganic conformations. Within the range of thermal fluctuations at room temperature, we identify chiral distortion patterns shared by the most stable structures. The following band structure and spin-texture calculations show distortion-induced spin-splitting, supporting the optical chirality observed in the experiments. |
Thursday, March 9, 2023 9:48AM - 10:00AM |
S41.00010: Spin coherence and spin relaxation in hybrid organic-inorganic perovskites MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3 Haochen Zhang, Zhixuan Bi, Zehua Zhai, Meng Ye, Han Gao, Hairen Tan, Yong Xu, Luyi Yang Metal halide perovskites have emerged as a new class of materials that are promising for semiconductor spintronics. Here we report a systematic investigation of coherent spin precession, spin dephasing and spin relaxation of electrons and holes in two hybrid organic-inorganic perovskites MA0.3FA0.7PbI3 and MA0.3FA0.7Pb0.5Sn0.5I3 using time-resolved Faraday rotation spectroscopy. With applied in-plane magnetic fields, we observe robust Larmor spin precession with spin dephasing times of hundreds of picoseconds. From these measurements, we determine the Lande g-factor, the inhomogeneous broadening of the g-factor, and spin dephasing time for both electrons and holes. Temperature-dependent measurements give further insight into the spin relaxation mechanisms and the strong influence of the lattice distortion on the g-factors. These results lay the foundation for further design and use of these new semiconductors for spin-based electronics. |
Thursday, March 9, 2023 10:00AM - 10:12AM |
S41.00011: Spin Polarized Charge Transport in 2D Chiral Perovskites Zihan Zhang, Zhenqi Hua, Peng Xiong, Hanwei Gao With outstanding optoelectrical performance and structural tunability, 2D organic-inorganic hybrid perovskites also manifest intriguing spintronic properties. As a proof of spin–orbital coupling, spin-dependent charge transport was reported in 2D chiral perovskites, where specific spin transport is impeded depending on the handedness of organic cations. Despite the observation, the structural origin of chirality as well as the spin polarization and transport mechanisms remain controversial. In this work, we integrated 2D chiral perovskites in van der Waals heterostructure based devices to characterize the spin polarized charge transport. Under varying magnetic field, the change in magnetoresistance was observed and revealed to be modulated by polarized spin. The spin transport was correlated with structural anisotropy of 2D chiral perovskite and electrical contact conditions. We hope this work can provide inspiration on realizing spintronic devices based on 2D chiral perovskites. |
Thursday, March 9, 2023 10:12AM - 10:24AM |
S41.00012: Temperature-dependent band gap of halide perovskite CsPbBr3 with first-principles methods Xiangzhou Zhu, Stefan A Seidl, Guy Reuveni, Christian Gehrmann, Sebastián Caicedo-Dávila, Omer Yaffe, David A Egger The electronic band gap is an important physical quantity for photovoltaic materials. Different from common semiconductors, band gaps of halide perovskites (HaPs) tend to slightly increase with temperature. It has been discussed that both lattice expansion and electron-phonon coupling influence the temperature dependence of the band gap. Meanwhile, as an anharmonic system, structural dynamics are expected to play an important role for optoelectronic properties of HaPs. In order to investigate this relationship, we perform molecular dynamics and Monte-Carlo calculations based on density functional theory and compare the temperature evolution of the band gap with results from reflectance measurements. Using CsPbBr3 as a model system, we find that dynamic fluctuations impact the band gap in these materials in a profound way. In particular, we demonstrate that thermal characteristics of it cannot be rationalized using the average crystal symmetry at a given temperature. Furthermore, by comparing different levels of vibrational theory, we find anharmonic vibrational contributions to have strong impacts on the magnitude and temperature-dependence of the band gap. Our work sheds light on the connections between structural dynamics and optoeletronic properties of HaPs. |
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