Terahertz sensing based on layered topological semimetal*

The emergent atomically thin layered materials enable the unique control of new phases of matter for high-performance electronics and optoelectronics.  One remarkable example is the recent discovered nonlinear Hall effect (NLHE) in topological semimetals, which is mediated by their diverging quantum geometrical properties [1-3]. It dictates a nontrivial second-order transverse current can be induced by an oscillating electric field, greatly enhanced by large Berry curvature dipoles at the band edges. This effect serves as a measure of the topological attributes inherent in quantum materials.

In this talk, I will present our exploration of such effect to enable a new efficient detection mechanism for electromagnetic waves with elevated frequency. In particular, we investigate the NLHE response in THz regime on a layered type-II Weyl semimetal. Leveraging a custom-designed and in-house fabricated device, we attained high and tunable photoresponsivity in few-layer semimetals. These findings illuminate a novel avenue for low-energy photon harvesting and transduction via quantum properties. Our findings also pave the way towards a wide range of THz applications in communication and imaging based on layered topological semimetals.

 

[1] Q. Ma et al., Observation of the nonlinear Hall effect under time-reversal-symmetric conditions, Nature 565, 337 (2019).

[2] K. Kang et al., Nonlinear anomalous Hall effect in few-layer WTe₂, Nature Materials 18, 324 (2019).

[3] J. Xiao et al., Berry curvature memory through electrically driven stacking transitions, Nature Physics 16, 1028 (2020).