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Download fileAnisotropic Picosecond Spin-Photocurrent from Weyl Semimetal WTe2
journal contribution
posted on 2020-03-14, 15:29 authored by Mengji Chen, Kyusup Lee, Jie Li, Liang Cheng, Qisheng Wang, Kaiming Cai, Elbert E. M. Chia, Haixin Chang, Hyunsoo YangThe
generation and detection of ultrafast spin current, preferably
reaching a frequency up to terahertz, is the core of spintronics.
Studies have shown that the Weyl semimetal WTe2 is of great
potential in generating spin currents. However, the prior studies
have been limited to the static measurements with the in-plane spin
orientation. In this work, we demonstrate a picosecond spin-photocurrent
in a Td-WTe2 thin film via a terahertz time domain spectroscopy
with a circularly polarized laser excitation. The anisotropic dependence
of the circular photogalvanic effect (CPGE) in the terahertz emission
reveals that the picosecond spin-photocurrent is generated along the
rotational asymmetry a-axis. Notably, the generated
spins are aligned along the out-of-plane direction under the light
normally incident to the film surface, which provides an efficient
means to manipulate magnetic devices with perpendicular magnetic anisotropy.
A spin-splitting band induced by intrinsic inversion symmetry breaking
enables the manipulation of a spin current by modulating the helicity
of the laser excitation. Moreover, CPGE nearly vanishes at a transition
temperature of ∼175 K due to the carrier compensation. Our
work provides an insight into the dynamic behavior of the anisotropic
spin-photocurrent of Td-WTe2 in terahertz frequencies and
shows a great potential for the future development of terahertz-spintronic
devices with Weyl semimetals.