University of Connecticut

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Condensed Matter Physics Seminar

Tuesday, November 10, 2020
10:00am – 11:00am

Storrs Campus
online

Professor Saroj Prasad Dash, Quantum Device Physics Laboratory, Dept. Microtechnology and Nanoscience, Chalmers University of Technology, Sweden

Spin Current in Topological Quantum Materials

An outstanding feature of topological quantum materials is their unique spin topology in the electronic band structures with an expected novel charge‐to‐spin conversion effects. In the Weyl semimetal candidate WTe2 we observed both conventional1 and unconventional2 charge‐to‐spin conversion effects at room temperature. In addition to the conventional spin Hall and Rashba–Edelstein effects, we also measured an unconventional charge‐to‐spin conversion component in WTe2. Such a large spin polarization can be possible in WTe2 due to a reduced crystal symmetry combined with its large spin Berry curvature, spin–orbit interaction with a novel spin‐texture of the Fermi states. We also investigated giant Rashba spin-orbit materials BiTeBr to detect the current induced spin polarization at room temperature.3 Furthermore, we integrated graphene with a topological insulator4,5 in van der Waals heterostructures6 to engineer proximity-induced spin-charge conversion phenomena. In these heterostructures, we experimentally demonstrate a gate-tunable spin-galvanic effect at room temperature, allowing for efficient conversion of a non-equilibrium spin polarization into a transverse charge current.7 These findings provide an efficient route for realizing all-electrical and gate-tunable spin phenomenon in topological materials and their heterostructures.

References:

1. Observation of charge to spin conversion in Weyl semimetal at room temperature. B Zhao, D Khokhriakov, Y Zhang, H Fu, B Karpiak, AM Hoque, X Xu, Y Jiang, B Yan, SP Dash. Physical Review Research 2 (1), 013286 (2020).

2. Unconventional charge-to-spin conversion Weyl Semimetal WTe2. B Zhao, B Karpiak, D Khokhriakov, A Johansson, AM Hoque, X Xu, Y Jiang, I Mertig, SP Dash. Advanced Materials, 2000818 (2020).

3. Electrically controlled spin injection from giant Rashba spin-orbit conductor BiTeBr" Z Kovács-Krausz et al., Nano Letters 20, 7, 4782–4791 (2020).

4. Origin and evolution of surface spin current in topological insulators A Dankert, P Bhaskar, D Khokhriakov, IH Rodrigues, B Karpiak, MV Kamalakar, S Charpentier, I Garate, SP Dash. Phys. Rev. B 97, 125414 (2018).

5. Room Temperature Electrical Detection of Spin Polarization in Topological Insulators A Dankert, J. Geur, M.V. Kamalakar, SP Dash; Nano Letters 15 (12) 7976 (2015).

6. Tailoring emergent spin phenomena in Dirac material heterostructures. D Khokhriakov, A. W. Cummings, K Song, M Vila, B Karpiak, A Dankert, S Roche and SP. Dash. Science Advances, 4, 9, eaat9349 (2018)

7. Gate-tunable Spin-Galvanic Effect in Graphene - Topological insulator van der Waals Heterostructures at Room Temperature. D Khokhriakov, AM Hoque, B Ka

Contact:

Prof. A. Balatsky.

Physics Department (primary), UConn Master Calendar

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