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(a) Low temperature longitudinal resistivity of the 20 nm sample. The electron density is in units of . Arrows indicate magnetic fields for integer LL filling factors. (b) Single particle LL energy diagram. LLs spaced by the cyclotron energy are split by and . The Fermi energy is located in the valley splitting for odd integer values of . For and , it is in the cyclotron gap and the Zeeman splitting, respectively. (c) of the 5.3 nm sample. (d) of the 4 nm sample.
(a) Typical temperature dependence of minima of the QH states at and 3. Arrhenius plots for different values of , , and . The solid lines are fits to the data. (b) The obtained energy gap for four samples with different well widths. The solid symbols represent the data obtained at and the open symbols are for .
Bare valley splitting estimated from the Shubnikov–de Haas oscillations. The average electric field in the QW region at the corresponding backgate voltage is also presented for future calculations.
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