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Pan, W., Tsui , D.C., Baldwin, K. W. West, W., Pfeiffer, L. N. , and Masuhara , N., Phys Rev. Lett . 106 , 206806 (

Effect of Disorder on Fractional Quantum Hall State Gregory S. Boebinger , Florida State University, DMR 0654118 High B/T Facility, University of Florida.

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Pan, W., Tsui , D.C., Baldwin, K. W. West, W., Pfeiffer, L. N. , and Masuhara , N., Phys Rev. Lett . 106 , 206806 (

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  1. Effect of Disorder on Fractional Quantum Hall State • Gregory S. Boebinger, Florida State University, DMR 0654118 High B/T Facility, University of Florida The symmetry properties of the fractional quantum Hall states at Landau level fillings of n=5/2 and 12/5 are of great interest because of the potential application in fault-tolerant quantum computing. To assess this potential it is critical to determine the impact of disorder on the low temperature properties of the 5/2 state. The activation energy gaps were therefore measured for two very different types of semiconductor structures for which the nature of the disorder is well characterized: (i) undoped hetero-junction field-effect transistors (HIGFETS), and (ii) symmetrically doped modulation quantum wells. The variation of the normalized energy gap  with inverse mobility -1 of these devices was observed to be strikingly different: (i) For long-ranged disorder (modulation-doped samples ), the gap  decreases sharply with increasing disorder (increasing -1), (ii) For short range disorder (HIGFETs) only a weak dependence was observed. Pan, W., Tsui, D.C., Baldwin, K. W. West, W., Pfeiffer, L. N. , and Masuhara, N., Phys Rev. Lett. 106, 206806 (2011).

  2. sample heat exchanger Effect of Disorder on Fractional Quantum Hall State Gregory S. Boebinger, Florida State University, DMR 0654118 High B/T Facility, University of Florida This work was enabled by unique ultra-low temperature instrumentation designed to cool the electrons in semiconductor devices to milliKelvin temperatures . The device shown at left employs socks of sintered silver to surround each electrical lead in a four-terminal conductivity measurement. The socks provide the required large surface area to a surrounding thermal bath of superfluid helium three. The helium bath temperature was typically 2 milliKelvin and the temperature of the electrons was determined (from measurements of the temperature dependence of the transverse resistivity) to be 4 milliKelvin. This work was a collaboration of scientists from Sandia National Laboratory and Princeton University with staff at the NHMFL High B/T Facility. Pan, W., Tsui, D.C., Baldwin, K. W. West, W., Pfeiffer, L. N. , and Masuhara, N., Phys Rev. Lett. 106, 206806 (2011).

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