Spin–orbit interaction effects on plasmons in double coupled quantum wires

We report on collective and single-particle excitations of quasi-one-dimensional (Q1D) electron gas, experiencing Rashba spin–orbit interaction (SOI), and embedded in semiconductor-based coupled symmetrical and asymmetrical biwires. We choose five different and most significant situations regarding the conditions of anisotropy and tunneling between the wires. As the Rashba SOI strength increases, we find extra undamped plasmon modes resulting from the SOI induced spin splitting of those modes appearing in the absence of SOI. We also find these modes remaining in the gap between the spin-down and spin-up SPE continua. We show similar effects occurring on the optical and acoustical plasmon modes; signatures of collective excitations appearing in biwires without tunneling. We find those plasmons related to the spin-down charge density fluctuations being of the most robust modes concerning the increase of the Rashba SOI strength.