Experimental Determination of Fractional Charge e/q in the FQHE and Its Application to the Destruction of States
We have recently demonstrated  that the LAUGHLIN/ HALDANE prediction e*=±e/q for the charge e* of quasiparticles excited across the energy gap Δ of FQHE ground states at v=p/q [2,3], a new fundamental quantum of nature, is consistent with experiment. The experimental probe of e* is σxx c=σxx(1/T=0) obtained from extrapolated values of ρxx c determined from activation data defined by σxx=σ xx c e−∆/kT. In a high quality, low density GaAs-GaAIAs heterojunction G139 (n= 1 x 1011 cm-2, µ= 1 x 106 cm2/Vs, 1600 Å spacer) we found that ρ xx c =c(e/q)2/h (independent of p) for some 13 fractional states at v=p/q with q=3, 5, 7 and 9, where the numerical constant c= 0.91 ±0.11. This result is not only consistent with e*=±e/q but strongly indicative of the existence of a minimum quasiparticle conductivity . In this paper, we report a study of σxx c and Δ in a higher density heterojunction G156 (n= 1 x 1011 cm−2, µ= 1.6 x 106 cm2/Vs, 400Å spacer) at two angles of the B-field to the sample plane normal, θ=0° and 47°. Our objectives are; (i) to examine the probe of e* for fractional states with q=3, 5 and 7 in a different structure and geometry, (ii) to compare normal and tilted field activation energies to examine the nature of the quasiparticle energy gaps and (iii) to apply the e* measurements for θ=0°and 47° to investigate what occurs when fractional states which are unpolarised at low field are ‘destroyed’ by the increased total field induced by tilt. Details of the FQHE ground state spin configurations for the N=0 Landau level are presented separately in these proceedings . Here we consider aspects relevant to the quasiparticle charge.
KeywordsLandau Level Fractional State Fractional Charge Fundamental Quantum 3Philips Research Laboratory
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