Magnetoelectric subbands in the one-dimensional to quasi-one-dimensional confined regime

We investigate the evolution of conductance quantization and subband structure in a weakly confined quasi-one-dimensional channel as a function of carrier density and perpendicular magnetic field. As the carrier density is reduced, the 2 e 2 / h plateau is progressively suppressed and an avoided crossing develops between the lowest two subbands in transconductance, indicating a strong intersubband coupling. This behavior is consistent with an interaction-driven restructuring of the electron system into a zigzag or two-row configuration in the regime of dominant Coulomb interactions. The application of a perpendicular magnetic field suppresses the anticrossing through enhanced magnetoelectric confinement, which reduces inter-row tunneling and hybridization via magnetic compression of the wave function. At intermediate fields ( ∼ 0.5 T ), further reduction of carrier density leads to the emergence of the 0.7 ( 2 e 2 / h ) feature coexisting with the restored 2 e 2 / h plateau. In addition, spin-split features, such as 1.5 ( 2 e 2 / h ) , begin to resolve in higher subbands in the low-density, weakly confined regime. At higher fields ( ∼ 0.7 T ), where the anticrossing is fully quenched, the low-density regime exhibits the coexistence of conductance features near 2 e 2 / h , 0.7 ( 2 e 2 / h ) , and 0.5 ( 2 e 2 / h ) . These observations indicate that perpendicular magnetic fields predominantly modify the orbital spectrum while leaving the strongly correlated spin sector intact. The resulting transport reflects the interplay between Coulomb interactions, exchange coupling, and Zeeman splitting, placing the system near the crossover between spin-coherent and spin-incoherent regimes.