Towards Advanced Chiral Sensors: Enhanced Helicity-Dependent Photocurrent in Ultrathin Topological Insulator Films

TL;DR

This paper investigates the mechanisms behind helicity-dependent photocurrent in ultrathin topological insulator films, proposing strategies to enhance their sensitivity for compact chiral sensors used in biomedical and material sciences.

Contribution

It reveals how to isolate and amplify helicity-dependent photocurrent in ultrathin TIs, enabling the design of high-performance, miniaturized chiral detectors.

Findings

HDPC is strongly amplified in ultrathin TI films.

Optimizing illumination, strain, and gating enhances HDPC.

Strategies to eliminate unwanted photoresponses improve detection accuracy.

Abstract

Chirality, a fundamental property of asymmetric structures, plays a crucial role in pharmaceutical, biological and chemical systems, offering a powerful tool for screening organic compounds. While the conventional optical chirality detectors are often bulky and involuted, the topological insulators (TIs) offer a promising platform for developing compact yet sensitive devices - owing to their inherent chirality. However, the complex interplay of photoresponses in TIs can limit the ultimate accuracy of chirality detection. Therefore, we here analyze the underlying mechanisms governing the photoresponses in TIs and reveal strategies to enhance the helicity-dependent photocurrent (HDPC). By attentively analyzing the symmetries and behavior of competing photoresponses, we show that it is possible to effectively eliminate unwanted contributions and isolate the HDPC. Moreover, we reveal that HDPC is strongly amplified in ultrathin TI films, and can be further enhanced by optimizing the illumination parameters, sensor strain and/or back gating. Our findings thereby provide a roadmap for design and optimization of miniaturized, high-performance TI chirality detectors, with potential to revolutionize chiral analysis in biomedical and material sciences.