Terahertz Nonlinear Hall Rectifiers Based on Spin‐Polarized Topological Electronic States in 1T‐CoTe₂

Abstract

The zero‐magnetic‐field nonlinear Hall effect (NLHE) refers to the second‐order transverse current induced by an applied alternating electric field; it indicates the topological properties of inversion‐symmetry‐breaking crystals. Despite several studies on the NLHE induced by the Berry‐curvature dipole in Weyl semimetals, the direct current conversion by rectification is limited to very low driving frequencies and cryogenic temperatures. The nonlinear photoresponse generated by the NLHE at room temperature can be useful for numerous applications in communication, sensing, and photodetection across a high bandwidth. In this study, observations of the second‐order NLHE in type‐II Dirac semimetal CoTe2 under time‐reversal symmetry are reported. This is determined by the disorder‐induced extrinsic contribution on the broken‐inversion‐symmetry surface and room‐temperature terahertz rectification without the need for semiconductor junctions or bias voltage. It is shown that remarkable photoresponsivity over 0.1 A W−1, a response time of approximately 710 ns, and a mean noise equivalent power of 1 pW Hz−1/2 can be achieved at room temperature. The results open a new pathway for low‐energy photon harvesting via nonlinear rectification induced by the NLHE in strongly spin–orbit‐coupled and inversion‐symmetry‐breaking systems, promising a considerable impact in the field of infrared/terahertz photonics.

Layer‐controlled nonlinear terahertz valleytronics in two‐dimensional semimetal and semiconductor PtSe2

“…For example, the semimetal TaAs, 18 the Topological Insulator 19 and graphene 20 have shown ultrafast currents that can be controlled through the polarization of the light excitation. Furthermore, semimetals have shown an important application potential as sensitive THz detectors 21–23 …”

“…Furthermore, semimetals have shown an important application potential as sensitive THz detectors. [21][22][23] However, the transition from semiconductor to semimetal and its effect on the THz photocurrents and nonlinearities generated in TMDs has not been investigated in a single material system, as typical TMDs rapidly transit from a direct to indirect gap with thicknesses greater than one ML. On the other hand, the recently discovered TMD PtSe 2 has garnered considerable interest.…”

Observation of highly anisotropic bulk dispersion and spin-polarized topological surface states in CoTe2

“…However, the electronic properties of another prospective candidate material in the series, CoTe 2 are yet to be explored 40 . CoTe 2 can crystallize in both trigonal (P 3m1) and orthorhombic (P nn2 and P nnm) forms.…”

Monolayer CrTe: a room temperature ferromagnetic half-metal

“…Two-dimensional (2D) materials are gaining increasing attention due to their broad range of physical properties with practical applications in various fields. These include electronics [1][2][3][4] , energy storage 5 , transport 4,6,7 , optoelectronics [8][9][10] , sensors [11][12][13][14][15] , catalysis [16][17][18][19] and magnetism [20][21][22][23][24][25] . Among 2D materials 20,21,[25][26][27][28][29][30][31][32][33][34][35] , 2D magnets are highly desirable for use in modern spintronics and data storage devices.…”