Quantized conductance in a CVD-grown nanoribbon with hidden Rashba effect

TL;DR

This study reports the observation of quantized conductance in a high-mobility Bi2O2Se nanoribbon, revealing a hidden Rashba effect that influences conductance behavior under magnetic fields, with implications for spintronics.

Contribution

It demonstrates quantized conductance in a CVD-grown Bi2O2Se nanoribbon due to a hidden Rashba effect, a novel observation linking conductance quantization to spin-orbit phenomena.

Findings

Quantized conductance plateaus up to 44×2e^2/h observed at zero magnetic field.

Conductance remains in multiples of 2e^2/h without Zeeman splitting under magnetic fields up to 12 T.

Plateau sequence exhibits Pascal triangle series, indicating size quantization effects.

Abstract

Quantized conductance in quasi-one-dimensional systems not only provides a hallmark of ballistic transport, but also serves as a gateway for exploring quantum phenomena. Recently, a unique hidden Rashba effect attracts tremendous attention, which arises from the compensation of opposite spin polarizations of a Rashba bilayer in inversion symmetric crystals with dipole fields, such as bismuth oxyselenide ($\mathrm{Bi}_{2}\mathrm{O}_{2}\mathrm{Se}$). However, investigating this effect utilizing conductance quantization is still challenging. Here we report the conductance quantization observed in a chemical vapor deposition (CVD)-grown high-mobility $\mathrm{Bi}_{2}\mathrm{O}_{2}\mathrm{Se}$ nanoribbon, where quantized conductance plateaus up to $44\cdot 2e^{2}/{h}$ ($e$ is the elementary charge, $h$ is the Planck constant, and the factor $2$ results from spin degeneracy) are achieved at zero magnetic field. Due to the hidden Rashba effect, the quantized conductance remains in multiples of $2e^{2}/{h}$ without Zeeman splitting even under magnetic field up to $12$ T. Moreover, within a specific range of magnetic field, the plateau sequence exhibits the Pascal triangle series, namely $(1,3,6,10,15\dots )\cdot 2e^{2}/{h}$, reflecting the interplay of size quantization in two transverse directions. These observations are well captured by an effective hidden Rashba bilayer model. Our results demonstrate $\mathrm{Bi}_{2}\mathrm{O}_{2}\mathrm{Se}$ as a compelling platform for spintronics and the investigation of emergent phenomena.