Crossover region of Rashba and Zeeman effect

초록

The electron spin in semiconductors can be controlled by either the spin-orbit coupling or the Zeeman term. The spin splitting due to the Rashba effect has been intensively studied by measuring the Shubnikov-de Haas (SdH) oscillations[1]. In most previous studies the Zeeman spin splitting was too small to be detected in the magnetic field range where the Rashba effect is studied. We study the spin states of two dimensional electron gas in the HgCdTe heterostructure by measuring the SdH oscillations under the perpendicular magnetic field without or with in-plane field, expecting that both the Rashba effect and the Zeeman term can be significant in the narrow-gap semiconductor. For HgCdTe, both of two effects can be large enough for us to be able to observe the crossover region between Rashba and Zeeman effects as a function of applied magnetic field. The crossover field can be defined as the field where the Rashba energy splitting is roughly equal to the Zeeman splitting. Fig.1 shows the SdH oscillation(∆Rxx) and the calculated density of state(DOS) at 2K, where the beating pattern is evident and it？fs node points are marked by down-arrows(？？). The filling factors(? for each minima of SdH near 6T change from odd numbers to integers, which indicates the crossover from the Rashba dominant region to the Zeeman dominant region, and this results are good agreement with the behaviour of the calculated DOS.