Tunable nonlinear hall effect at room temperature in tellurium

Recently, the research team led by Prof. ZENG Changgan and Associate Researcher LI Lin from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) have discovered significant nonlinear Hall and wireless rectification effects at room temperature in elemental semiconductor tellurium (Te). The research was published in Nature Communications.

Nonlinear Hall effect (NLHE) is a second-order response to an applied alternating current (AC), which can generate second-harmonic signals without introducing external magnetic field. NLHE is of considerable scientific interest due to its potential applications in frequency-doubling and rectifying devices. However, previous studies have faced challenges such as low Hall voltage outputs and low working temperatures, hindering practical applications of NLHE. Currently, NLHE at room temperature has only been observed in Dirac semimetal BaMnSb₂​ and the Weyl semimetal TaIrTe₄​, both of which exhibit relatively small voltage outputs and lacked tunability.

To address the challenges, the research team made a groundbreaking decision to search for systems exhibiting exceptional NLHE in semiconductor materials. They studied the nonlinear response of Te, a narrow-bandgap semiconductor characterized by its one-dimensional atom helical chain structures, which inherently breaks inversion symmetry, making Te an ideal candidate.

The team discovered a significant NLHE at room temperature in Te thin flakes, with tunable Hall voltage outputs modulated by external gate voltages. At 300 K, the maximum second-harmonic output can reach 2.8 mV, which is an order of magnitude higher than previous records. Through further experiments and theoretical analysis, they found that the observed NLHE in Te thin flakes is primarily driven by extrinsic scattering, with surface symmetry breaking of the thin flake structure playing a crucial role.

Building on this breakthrough, the team replaced AC current with radiofrequency (RF) signals, realizing wireless RF rectification in Te thin flakes. They achieved stable rectified voltage output over a broad frequency range of 0.3 to 4.5 GHz. Unlike conventional rectifiers that rely on p-n junctions or metal-semiconductor junctions, the Hall rectifier based on Te's inherent properties offers a broadband response under zero bias, making it an attractive option for developing efficient and reliable energy harvesting and wireless charging devices.

By revealing the underlying mechanisms of NLHE in Te, this study not only enhances our understanding of nonlinear transport in solid materials, but also opens up new possibilities for the future development of advanced electronic devices.

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