Recent advancements in semiconductor research have unveiled an exciting phenomenon known as the nonlinear Hall effect (NLHE), which has shown great promise for practical applications in electronic and wireless technologies. This effect, characterized as a second-order response to alternating current (AC), uniquely generates second-harmonic signals independent of external magnetic fields. However, earlier investigations into NLHE have largely been restricted by limitations such as low Hall voltage outputs and temperature dependencies, curtailing its practical applicability. Until now, notable observations of NLHE at room temperature have been confined to specific materials, namely Dirac semimetal BaMnSb2 and Weyl semimetal TaIrTe4, which, while interesting, demonstrate low voltage outputs and limited tunability.
In an innovative effort to overcome these hurdles, a research team led by Prof. Zeng Changgan and Associate Researcher Li Lin from the University of Science and Technology of China turned their attention to elemental semiconductor tellurium (Te). This semiconductor is distinguished by its unique one-dimensional atomic helical chain structures that inherently disrupt inversion symmetry, which is crucial for enabling a robust NLHE. The researchers meticulously explored the nonlinear responses of thin flakes of Te, ultimately uncovering significant NLHE at ambient temperature—an achievement considered groundbreaking within the field.
Breakthrough Findings: Enhancing Hall Voltage Output
The findings from this research are nothing short of revolutionary. The team reported a remarkable maximum second-harmonic output of 2.8 mV at 300 K, far surpassing previous records associated with NLHE in other semiconductor materials. This newfound capability arises from the excitation of the NLHE primarily through extrinsic scattering, where the symmetrical properties of the thin flake structures play a vital role. The ability to modulate the Hall voltage outputs via external gate voltages adds an exciting layer of tunability, vastly improving the adaptability of NLHE for practical uses in electronic applications.
Building on their NLHE findings, the researchers made a significant leap by substituting traditional AC currents with radiofrequency (RF) signals, thereby achieving wireless RF rectification using Tellurium. The rectified voltage output was stable across a wide frequency spectrum, from 0.3 to 4.5 GHz. Unlike standard rectifiers contingent on p-n junctions or metal-semiconductor junctions, this Hall rectifier exploits the inherent properties of Te, offering a unique broadband response even under zero bias. This dynamic aspect makes it particularly appealing for future endeavors in energy harvesting and wireless charging systems, representing a potential cornerstone for next-generation electronic devices.
The implications of these findings extend beyond immediate practical applications; they might pave the way for enhanced understanding of nonlinear transport phenomena in solid materials. By elucidating the mechanisms underpinning NLHE within tellurium, this research opens doors to a new frontier in semiconductor technology, promising advancements in both performance and versatility of electronic devices. As research continues to explore the depths of semiconductor physics, tellurium could emerge as a central figure in developing cutting-edge technologies, driving innovation in energy solutions for an increasingly wireless future.