Modulation Of Bilayer Quantum Hall States By Tilted-Field-Induced Subband-Landau-Level Coupling

We study effects of tilted magnetic fields on energy levels in a double-quantum-well (DQW) system, focusing on the coupling of subbands and Landau levels (LLs). The subband-LL coupling induces anticrossings between LLs directly manifested in the magnetoresistance. The anticrossing gap becomes larger than the spin splitting at the tilting angle theta similar to 20 degrees and larger than the cyclotron energy at theta similar to 50 degrees, demonstrating that the subband-LL coupling exerts a strong influence on quantum Hall states even at a relatively small theta and plays a dominant role for larger theta. We also find that when the DQW potential is asymmetric, LL coupling occurs even within a subband. Calculations including higher-order coupling reproduce the experimental results quantitatively well.