Simultaneous excitation of spins and pseudospins in the bilayer ν=1 quantum Hall state

Abstract

The tilting angular dependence of the energy gap was measured in the bilayer quantum Hall state at the Landau level filling ν = 1 by changing the density imbalance between the two layers. The observed gap behavior shows a continuous transformation from the bilayer balanced density state to the monolayer state. Even a sample with 33 K tunneling gap shows the same activation energy anomaly reported by Murphy et al. [1]. We discuss a possible relation between our experimental results and the quantum Hall ferromagnet of spins and pseudospins.

Spin gap in the two-dimensional electron system ofGaAs∕AlxGa1−xAssi

“…[4] that introducing a parallel component of the magnetic field allows determination of the spin of the lowest-lying charged excitations by the increase in the activation energy with parallel field. The experimental results indicated that the excitations at ν = 1 are accompanied with seven electron spin flips, while at ν = 3 and 5 only a single spin flips [4,10]. This is consistent, in principle, with the predictions of the skyrmion approach.…”

“…[3,4,5,6,7,8,9,10]). Strongly enhanced values of the spin gap in the 2D electron system in GaAs/AlGaAs heterostructures were found by measurements of the activation energy for the longitudinal resistivity minimum at filling factor ν = 1, 3, and 5 [3,4,5].…”

SU(4)skyrmions and activation energy anomaly in bilayer quantum Hall systems

“…11,14,15 It seems that the exchange energy has been underestimated by making the derivative expansion. It is necessary to go beyond the present approximation to fully understand the problem.…”

“…Terasawa et al 15 have measured the activation energy by controlling the tilting angle ⌰ at the balanced point in a sample with ⌬ SAS Ӎ 33 K. We have fitted their data [ Fig. 6] by the ppinexcitation formula (9.11) and by the generic formula (9.15).…”

“…To fit the data by the theoretical formula (9.15), we have adjusted the activation energy at ⌰ = 0 with the experimental value, and assumed that the flipped spin number N ppin and the flipped pseudospin number N ppin are constant for all values of the tilting angle. 15). To fit the data by the theoretical formula, we have adjusted the activation energy at ⌰ = 0 with the experimental value.…”