氧化物界面的准二维电子气（q-2DEG）为研究强关联电子系统中的量子现象提供了一个平台。本文研究了高迁移率（La $_{0.3}$ Sr $_{0.7}$）（Al $_{0.65}$ Ta $_{0.35}$）O $_{0.3}$ /SrTiO $_{0.3}$（LSAT/STO）界面的输运性质。在氧气退火之前，生长界面表现出两个子带的高电子密度和电子占有率：高迁移率电子（$μ_1\approx{10^4}$ cm $^2$ V $^{-1}$ s $^{-1}$ at 2 K）占据较低能量的$3d_{xy}$子带，而低迁移率电子（$μ_1\approx{10^3}$ cm $^{2}$ V $^{-1}$ s $^{-1}$ at 2 K）在较高能量的$3d_{xz/yz}$主导的子带中传播。通过在氧气中退火去除氧空位后，只有单一类型的3dxy电子保留在退火界面处，在2 K和$0.7m_e$的有效质量下显示出低于9 T的可调谐Shubnikov-de Haas（SdH）振荡。相比之下，没有观察到振荡生长的界面，即使当电子迁移率增加到$50,000$ cm $^{2}$ V $^{-1}$ s $^{-1}$的门控电压。我们的研究结果揭示了载流子迁移率和子带占有率在调节氧化物界面量子输运中的重要作用。
英文摘要：
The quasi two-dimensional electron gas (q-2DEG) at oxide interfaces provides a platform for investigating quantum phenomena in strongly correlated electronic systems. Here, we study the transport properties at the high-mobility (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)O$_{0.3}$/SrTiO$_{0.3}$ (LSAT/STO) interface. Before oxygen annealing, the as-grown interface exhibits a high electron density and electron occupancy of two subbands: higher-mobility electrons ($μ_1\approx{10^4}$ cm$^2$V$^{-1}$s$^{-1}$ at 2 K) occupy the lower-energy $3d_{xy}$ subband, while lower-mobility electrons ($μ_1\approx{10^3}$ cm$^{2}$V$^{-1}$s$^{-1}$ at 2 K) propagate in the higher-energy $3d_{xz/yz}$-dominated subband. After removing oxygen vacancies by annealing in oxygen, only a single type of 3dxy electrons remain at the annealed interface, showing tunable Shubnikov-de Haas (SdH) oscillations below 9 T at 2 K and an effective mass of $0.7m_e$. By contrast, no oscillation is observed at the as-grown interface even when electron mobility is increased to $50,000$ cm$^{2}$V$^{-1}$s$^{-1}$ by gating voltage. Our results reveal the important roles of both carrier mobility and subband occupancy in tuning the quantum transport at oxide interfaces.
Anisotropic Magneto Resistance and Planar Hall Effect at the LaAlO$_3$/SrTiO$_3$ Heterointerfaces: Effect of Carrier Confinement on Magnetic Interactions
