Dynamical evolution of anisotropic response of type-II Weyl semimetal TaIrTe4 under ultrafast photoexcitation

Abstract

Layered type-II Weyl semimetals, such as WTe2, MoTe2, and TaIrTe4 have been demonstrated as a supreme photodetection material with topologically enhanced responsivity and specific sensitivity to the orbital angular momentum of light. Toward future device applications with high performance and ultrafast response, it is necessary to understand the dynamical processes of hot carriers and transient electronic properties of these materials under photoexcitation. In this work, mid-infrared ultrafast spectroscopy is performed to study the dynamical evolution of the anisotropic response of TaIrTe4. The dynamical relaxation of photoexcited carriers exhibits three exponential decay components relating to optical/acoustic phonon cooling and subsequent heat transfer to the substrate. The ultrafast transient dynamics imply that TaIrTe4 is an ideal material candidate for ultrafast optoelectronic applications, especially in the long-wavelength region. The angle-resolved measurement of transient reflection reveals that the reflectivity becomes less anisotropic in the quasi-equilibrium state, indicating a reduction in the anisotropy of dynamical conductivity in presence of photoexcited hot carriers. The results are indispensable in material engineering for polarization-sensitive optoelectronics and high field electronics.

A Polarization-Sensitive Self-Powered Photodetector Based on a p-WSe2/TaIrTe4/n-MoS2 van der Waals Heterojunction

“…Recently, the angle-resolved polarized Raman (ARPR) spectra of TaIrTe 4 have been reported as direct proof of the absence of inversion symmetry in TaIrTe 4 , which indicates the strong in-plane optical and electrical anisotropy in TaIrTe 4 flakes . Also, the dynamical evolution of the anisotropic response for TaIrTe 4 has been studied by mid-infrared ultrafast spectroscopy . In addition, photodetectors based on Weyl semimetals are expected to perform a more extreme performance than semiconductors in terms of self-powered operation, an ultrabroad band, and high sensitivity on account of their topologically protected band structures .…”

Direct Light Orbital Angular Momentum Detection in Mid‐Infrared Based on the Type‐II Weyl Semimetal TaIrTe4

“…The topological charge of a scalar OAM beam can be resolved using the photocurrent plateau driven by the OPGE response. Combined with previous experimental demonstrations that exhibit that TaIrTe 4 is sensitive to both the direction of linearly polarized light owing to its anisotropic photocurrent response [ 13d,21 ] and the helicity of light owing to the chiral nature of the Weyl cone as a Weyl semimetal, [ 22 ] TaIrTe 4 represents a class of topological semimetals that is suitable for both OAM and polarization‐sensitive photodetection in the mid‐infrared waveband. A mixture of a variety of OAM orders and the polarization of light may be resolved simultaneously by using a small matrix of well‐designed electrodes.…”

Ultrafast photothermoelectric effect in Dirac semimetallic Cd3As2 revealed by terahertz emission

“…The instantaneous transient states after the photoexcitation can support transient ambipolar transport and provide ambipolar TE effect. As such response is usually on the picosecond timescale in semimetals 9 , 12 – 14 , such transient current is difficult to be measured by conventional transport measurement. Instead, the picosecond transient current emits electronmagnetic wave in terahertz (THz) frequency range, thus can be characterized by measuring its THz emission 15 – 17 .…”

“…With ultrahigh electron mobility and ultrafast carrier dynamics, topological semimetals are suitable for such applications 11 , 13 , 18 , 19 . In these devices, the carriers are accelerated by the electric field which is similar to the photoexcited state after photoexcitation 9 , 14 , 20 – 24 . It is equally important for optoelectronic-related applications, such as light-harvesting and detection, where light interaction with materials is involved and the simultaneous transient optical process involves the TE response of the materials 8 , 10 , 11 , 25 – 27 .…”