Temperature- and light-driven crossover behavior in quantum Hall scaling of a wide HgTe quantum well

Abstract

HgTe quantum wells (QWs) with inverted band structures and strong spin–orbit coupling provide a versatile platform for studying topological quantum transport. Quantum Hall scaling near plateau–plateau transitions provides a sensitive probe of the crossover between localized and extended states. Here we investigate plateau–plateau transitions in a 23 nm-wide HgTe QW with a reduced effective energy gap, where macroscopic transport is not strictly limited to a single effective two-dimensional channel. By analyzing the temperature- and illumination-dependent maximum Hall slope, we extract the scaling exponent κ, which is treated here as an effective scaling exponent derived from macroscopic transport, and identify a pronounced temperature-driven crossover. At low temperatures, κ deviates from commonly reported values and evolves toward the range typically observed in conventional two-dimensional systems at elevated temperatures, while Landau-level quantization remains clearly identifiable. Infrared illumination further modifies the extracted κ and shifts the crossover toward lower temperatures, reflecting an effective modulation of the transport response. These results show that quantum Hall scaling in wide HgTe QWs is influenced by the interplay between disorder-related dissipative transport and finite phase coherence, highlighting the applicability and limitations of scaling analysis beyond the single effective two-dimensional channel regime.