Evidence for Skyrmions and Single Spin Flips in the Integer Quantized Hall Effect

Abstract

We have employed tilted-field magneto-transport measurements of the energy gap for the odd-integer quantized Hall states at Landau level filling factors ν = 1,3 and 5 to determine the spin of thermally excited quasielectronquasihole pairs. At ν = 1 our data show that as many as 7 electron spin flips accompany such excitations, while at ν = 3 and 5 apparently only a single spin flips. These results lend support to the recent suggestions that "Skyrmionic" quasiparticles are the lowest-lying charged excitations of the fully-polarized ν = 1 quantum Hall fluid but are not at the higher odd-integer fillings.Typeset using REVT E X 1

Skyrmions in quantum Hall systems with realistic force laws

“…The low-energy charged excitations are predicted to be charged spin-textures if the Zeeman energy is less than 0.054(e 2 /4πǫǫ 0 ℓ) [7,1], which is typically the case in GaAs devices [8]. Experimental studies of such systems show that the charged excitations at ν = 1 do carry large spin [4][5][6], in good agreement with current theory.At higher odd filling fractions [9,10], the low-energy properties in the strong-field limit depend only on the electrons in the uppermost Landau band. Consequently, such systems appear much like a system at ν = 1, differing only in the form of the single-particle states available to the electrons.…”

“…For typical values of this width, in the limit of vanishing Zeeman energy we find that the low-energy excitations are "skyrmions" not only at ν = 1 but also at higher filling fractions. Our results lead to the prediction that, in typical samples, abrupt transitions to charged excitations with very large spins should be observable at filling fractions higher than ν = 1 if the Zeeman energy is reduced sufficiently.PACS Number: 73.40.HmTo appear in Physical Review BThere has recently been a great deal of theoretical and experimental activity studying spin-related phenomena in two-dimensional electron systems in the quantum Hall regime [1][2][3][4][5][6]. In such systems, the combination of strong Landau quantization and extremely small Zeeman energy leaves the primary role in determining the groundstate spin-correlations to the many-body interactions.…”

Magneto-optical probe of quantum Hall states in a wide parabolic well modulated by random potential

“…28 We examined the magneto-PL measured at the tilted angle θ = 70 • . Assuming in GaAsg = 0.01, 14 the angle tilting out to 70 • will result ing = 0.017, which is close to the theoretical limit. Indeed, as shown in Fig.…”

Fractional quantum Hall effect of two-dimensional electrons in high-mobility Si/SiGe field-effect transistors

“…Celebrated examples include Skyrmions in systems with small Zeeman splitting [6,7], even-denominator FQH states [8,9], and the excitonic superfluid in bilayer systems [10]. While much effort towards the understanding of the roles of spins, layers, and subbands in the FQH regime has been made using high-quality GaAs quantum wells, experimental studies on the effects of valleys have been relatively sparse, only a few reports on 2D electrons in Si [11,12] and AlAs [13][14][15][16] available, partly due to the less impressive material quality of multi-valley semiconductors.…”