Spin to Charge Conversion at Room Temperature by Spin Pumping into a New Type of Topological Insulator:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>α</mml:mi></mml:mrow></mml:math>-Sn Films

TLDR

The study investigates spin‑to‑charge conversion by spin pumping into the Dirac cone of α‑Sn. The authors compare spin‑pumping results with time‑resolved ARPES relaxation times to estimate the ultimate spin‑to‑charge conversion potential of α‑Sn. ARPES confirms the α‑Sn Dirac cone survives Ag capping, and resonant spin pumping from Fe/Ag into α‑Sn at room temperature generates a lateral charge current via the inverse Edelstein effect with a length exceeding that of Rashba interfaces, underscoring α‑Sn’s promise for spin‑to‑charge conversion.

Abstract

We present experimental results on the conversion of a spin current into a charge current by spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) {\alpha}-Sn[1-3]. By angle-resolved photoelectron spectroscopy (ARPES) we first confirm that the Dirac cone at the surface of {\alpha}-Sn (0 0 1) layers subsists after covering with Ag. Then we show that resonant spin pumping at room temperature from Fe through Ag into {\alpha}-Sn layers induces a lateral charge current that can be ascribed to the Inverse Edelstein Effect[4-5]. Our observation of an Inverse Edelstein Effect length[5-6] much longer than for Rashba interfaces[5-10] demonstrates the potential of the TI for conversion between spin and charge in spintronic devices. By comparing our results with data on the relaxation time of TI free surface states from time-resolved ARPES, we can anticipate the ultimate potential of TI for spin to charge conversion and the conditions to reach it.