Dresden 2017 – scientific programme

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DS: Fachverband Dünne Schichten

DS 19: Fundamentals of Perovskite Photovoltaics III (jointly with CPP/HL)

DS 19.6: Talk

Tuesday, March 21, 2017, 11:15–11:30, ZEU 222

Giant Rashba Splitting in (CH₃NH₃)PbBr₃ Organic-Inorganic Perovskite — Daniel Niesner¹, Max Wilhelm¹, Ievgen Levchuk², Andres Osvet², Shreetu Shrestha², Miroslaw Batentschuk², Christoph Brabec^{2, 3}, and •Thomas Fauster¹ — ¹Lehrstuhl für Festkörperphysik, FAU Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany — ²I-MEET, Department of Materials Science and Engineering, FAU Erlangen-Nürnberg, Martensstr. 7, D-91058 Erlangen, Germany — ³ZAE Bayern, Haberstr. 2a, D-91058 Erlangen, Germany

A Rashba-type spin-split band structure has been predicted for organic-inorganic perovskite semiconductors. The effect has been proposed as one of the origins of the exceptionally long carrier lifetimes in the materials, forming the basis of their successful application in optoelectronics. Using angle-resolved photoelectron spectroscopy, we investigate the band structure of (CH₃NH₃)PbBr₃ single crystals cleaved in ultrahigh vacuum. The orthorhombic low-temperature phase and the cubic room-temperature phase are studied. We apply a modified leading-edge method to identify the dispersion of the valence band edge. It reveals two valence band maxima, separated in k-space by 0.043 Å⁻¹. The dispersion is indicative of Rashba splitting. This interpretation is supported by the observation of circular dichroism in the orthorhombic phase. Extracted Rashba parameters of α_o=7± 1 eV Å and α_c=11± 4 eV Å in the orthorhombic and the cubic phase are amongst the largest reported to date.