Title: Hidden-Rashba-driven Absence of Odd-integer Quantized States in an Oxide Quantum Hall System

Abstract: The discovery of the quantum Hall effect in 1980, a turning point in condensed matter physics, has inspired exploring emergent quantized states regarding novel electron states, band topologies and spin textures. Owing to the lifted degeneracies universally-existing, most quantum Hall systems host both even- and odd-integer quantum Hall plateaus simultaneously. Selective control of these quantized states is of great significance to understand the exotic ground states and manipulate the spin textures in quantum Hall systems; however, it remains challenging. Here we demonstrate the absence of odd-integer state in inversion-symmetric Bi2O2Se quantum Hall system driven by the unique hidden Rashba effect. Pronounced quantum oscillations and only even-integer quantized plateaus were observed in the few-layer Bi2O2Se films epitaxially grown on SrTiO3. However, after reducing the thickness of epitaxial Bi2O2Se film to one unit cell limit with giant Rashba parameter of 440 meV.A, both odd- and even-integer states can show up simultaneously in this 2D Janus film. Theoretical calculations revealed that such absence of odd-integer states, i.e., a suppressed Zeeman splitting, stems from a unique hidden Rashba effect in the inversion-symmetric Bi2O2Se. However, this hidden Rashba effect can be further broken down due to tunable inversion-symmetry breaking. Our work highlights the extraordinary controllability of quantized states at the atomic level and further provides an unprecedented path to explore and handle novel spin textures and ground states.