Studies of Skyrmions at ν=1 in the Limit of Zero g-factor. (2008)
D. R. Leadley, R. J. Nicholas, D. K. Maude, A. N. Utjuzh, J. C. Portal, J. J. Harris, ...
In a two-dimensional electron gas at ν=1 (where the filling factor ν=neh/eB measures how many Landau levels (LL) are filled) the ground state should be regarded as a ferromagnet since all the spin...
FRACTIONAL QUANTUM HALL EFFECT MEASURED IN A SPIN DEGENERATE ELECTRON GAS (2008)
D. R. Leadley, R. J. Nicholas, D. K. Maude, J. C. Portal, J. J. Harris
The influence of spin on the Fractional Quantum Hall Effect is investigated in GaAs-GaAlAs heterojunctions in a filling factor region where both spin states of the lowest Landau level are occupied....
The dependence of the Composite Fermion effective mass on carrier density and Zeeman energy (2008)
R J Nicholas, D R Leadley, M S Daly, P Gee, J Singleton, ...
Abstract. Measurements of the temperature-dependent resistivity of high-mobility GaAs/GaAlAs heterojunctions are used to measure the effective mass of Composite Fermions (CF). The CF effective mass...
Measurements of composite Skyrmions at filling factor 1/3 (2008)
D. R. Leadley, R. J. Nicholas, D. K. Maude, A. N. Utjuzh, J. C. Portal, J. J. Harris, ...
Measurements of the fractional quantum Hall effect energy gaps at high pressures are presented that provide evidence for the existence of composite Skyrmions. Just as charged spin textures known as...
Critical Collapse of the Exchange Enhanced Spin Splitting in 2-D Systems (2007)
D. R. Leadley, R. J. Nicholas, J. J. Harris, C. T. Foxon
The critical filling factor νc where Shubnikov-de Haas oscillations become spin split is investigated for a set of GaAs-GaAlAs heterojunctions. Finite temperature magnetoresistance measurements are...
Cyclotron Resonance study of the electron and hole velocity in graphene monolayers (2007)
Deacon, R. S., Chuang, K-C., Nicholas, R. J., Novoselov, K. S., Geim, A. K.
We report studies of cyclotron resonance in monolayer graphene. Cyclotron resonance is detected using the photoconductive response of the sample for several different Landau level occupancies. The...
Superlattice Magnetophonon Resonances in Strongly Coupled InAs/GaSb Superlattices (2007)
Deacon, R. S., Henriques, A. B., Nicholas, R. J., Shields, P. A.
We report an experimental study of miniband magnetoconduction in semiconducting InAs/GaSb superlattices. For samples with miniband widths below the longitudinal optical phonon energy we identify a...
Mortimer, I. B., Nicholas, R. J.
We report studies of the temperature dependence of the photoluminescence efficiency of single walled carbon nanotubes which demonstrate the role of bright and dark excitons. This is determined by the...
Monte Carlo Studies of Miniband Conduction in Extreme Type-II Superlattices (2006)
A.B. Henriques, R. Deacon, R. J. Nicholas
Monte Carlo Studies of Miniband Conduction in Extreme Type-II Superlattices
Current-driven breakdown of the quantized Hall states of a broken-gap 2D electron-hole system (2006)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
We report results from experimental studies on the current driven breakdown of the quantum Hall effect in an InAs/GaSb-based electron-hole system. We find that the critical currents observed in this...
Chirality-dependent boron-mediated growth of nitrogen-doped single-walled carbon nanotubes (2005)
Wiltshire, J. G., Li, L. J., Herz, L. M., Nicholas, R. J., Glerup, M., Sauvajol, J. L., ...
Monte Carlo studies of miniband conduction in extreme type-II superlattices (2004)
Henriques,A. B., Deacon,R., Nicholas,R. J.
Miniband charge transport was investigated by Monte Carlo simulations of electronic motion in short period superlattices of type-II energy band alignment (InAs/GaSb composition). The strong decrease...
Far-infrared modulated photoluminescence spectroscopy of InSb/GaSb quantum dot structures (2003)
Child, R. A., Nicholas, R. J., Mason, N. J., Shields, P. A., Wells, J-P. R., Bradley, I. V., ...
The first far-infrared modulated photoluminescence (FIRM-PL) measurements in InSb/GaSb quantum dots have been performed. Far-infrared absorption is found to both enhance and suppress the quantum dot...
Insulating states of a broken-gap two-dimensional electron-hole system (2003)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
Quantum Hall and insulating states of a 2-D electron-hole system (2003)
Takashina, K., Nicholas, R. J., Mason, N. J., Maude, D. K., Portal, J. C.
Breakdown of the QHE in an electron-hole system (2003)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
Metallic and insulating states of a broken-gap 2-D electron-hole system (2003)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
Observation of magnetophotoluminescence from a GaN/AlxGa1-xN heterojunction (2002)
Shields, P A, Nicholas, R J, Takashina, K, Grandjean, N, Massies, J
Observation of magnetophotoluminescence from a GaN/AlxGa1-xN heterojunction (2002)
Shields, P A, Nicholas, R J, Takashina, K, Grandjean, N, Massies, J
Petchsingh, C., Nicholas, R. J., Takashina, K., Mason, N. J., Zeman, J.
We report a study of cyclotron resonance (CR) in a bilayer- bipolar InAs/GaSb structure and the influence of the spatial separation between the electrons and holes. At low magnetic fields we find...
Chughtai, R., Zhitomirsky, V., Nicholas, R. J., Henini, M.
Measurements of the reflectivity of a 2-D electron gas are used to deduce the polarization of the Composite Fermion hole system formed for Landau level occupancies in the regime 1
Roberts, M., Chung, Y. C., Lyapin, S., Mason, N. J., Nicholas, R. J., Klipstein, P. C.
We have measured the current-voltage (I-V) of type II InAs/GaSb/InAs double heterojunctions (DHETs) with 'GaAs like' interface bonding and GaSb thickness between 0-1200 \AA. A negative differential...
Free carrier effects in gallium nitride epilayers: the valence band dispersion (2001)
Shields, P. A., Nicholas, R. J., Peeters, F. M., Beaumont, B., Gibart, P.
The dispersion of the A-valence-band in GaN has been deduced from the observation of high-index magneto-excitonic states in polarised interband magneto-reflectivity and is found to be strongly...
Shields, P. A., Nicholas, R. J., Grandjean, N., Massies, J.
A re-ordered valence band in GaN/AlGaN quantum wells with respect to GaN epilayers has been found as a result of the observation of an enhanced g-factor in magneto-luminescence spectra in fields up...
Resonant LO phonon enhanced conductivity in GaAs-AlAs superlattices (2001)
Dalton, K. S. H., Hales, V. J., Symons, D. M., Nicholas, R. J., Gassot, P., Maude, D. K., ...
Breakdown of the quantum Hall effect in an electron-hole system (2001)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
Edge effects in an insulating state of an electron-hole system in magnetic field (2001)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
Insulating states of a 2-dimensional electron-hole system in high magnetic field (2001)
Takashina, K., Nicholas, R. J., Kardynal, B., Mason, N. J., Maude, D. K., Portal, J. C.
A digital quantum Hall effect (2000)
Nicholas, R. J., Lakrimi, M., Kardynal, B., Khym, S., Mason, N. J., Rehman, J., ...
Cyclotron resonance in an asymmetric electron-hole InAs/GaSb DHET structure (2000)
Petchsingh, C., Nicholas, R. J., Poulter, A. J. L., Hales, V. J., Mason, N. J., Walker, P. J.
Metal-insulator oscillations in a two-dimensional electron-hole system (2000)
Nicholas, R. J., Takashina, K., Lakrimi, M., Kardynal, B., Khym, S., Mason, N. J., ...
Metal-Insulator oscillations in a Two-dimensional Electron-Hole system (1999)
Nicholas, R. J., Takashina, K., Lakrimi, M., Kardynal, B., Khym, S., Mason, N. J., ...
The electrical transport properties of a bipolar InAs/GaSb system have been studied in magnetic field. The resistivity oscillates between insulating and metallic behaviour while the quantum Hall...
Searches for Skyrmions in the Limit of Zero g-Factor (1998)
Leadley, D. R., Nicholas, R. J., Maude, D. K., Utjuzh, A. N., Portal, J. C., Harris, J. J., ...
Energy gaps have been measured for the ferromagnetic quantum Hall effect states at v=1 and 3 in GaAs/GaAlAs heterojunctions as a function of Zeeman energy, which is reduced to zero by applying...
Critical Collapse of the Exchange Enhanced Spin Splitting in 2-D Systems (1998)
Leadley, D. R., Nicholas, R. J., Harris, J. J., Foxon, C. T.
The critical filling factor v_c where Shubnikov-de Haas oscillations become spin split is investigated for a set of GaAs-GaAlAs heterojunctions. Finite temperature magnetoresistance measurements are...
Magnetic breakdown in the semimetallic InAs/GaSb system. (1998)
Symons, D. M., Lakrimi, M., Nicholas, R. J., Maude, D. K., Portal, J. C., Mason, N. J., ...
Theory of the band mixing induced negative magnetoresistance in broken gap superlattices. (1998)
Symons, D. M., Peeters, F. M., Lakrimi, M., Khym, S., Portal, J. C., Mason, N. J., ...
Searches for skyrmions in the limit of zero g-factor. (1998)
Leadley, D. R., Nicholas, R. J., Maude, D. K., Utjuzh, A. N., Portal, J. C., Harris, J. J., ...
Measurement of composite skyrmions at filling factor 1/3. (1998)
Leadley, D. R., Nicholas, R. J., Maude, D. K., Utjuzh, A. N., Portal, J. C., Harris, J. J., ...
Skyrmions and composite fermions in the limit of vanishing Zeeman energy (1998)
R J Nicholas, D R Leadley, D K Maude, J C Portal, J J Harris, C T Foxon
Abstract. We describe the properties of a strongly interacting two-dimensional (2D) electron gas in high magnetic fields whose properties can be described in terms of the formation of composite...
Searches for skyrmions in the limit of zero g-factor (1998)
D R Leadley, R J Nicholas, D K Maude, A N Utjuzh, J C Portal, J J Harris, ...
Abstract. Energy gaps have been measured for the ferromagnetic quantum Hall effect states at ν = 1 and 3 in GaAs/Ga0.7Al0.3As heterojunctions as a function of Zeeman energy, which is reduced to zero...
Fractional Quantum Hall Effect Measurements at Zero g-Factor (1997)
Leadley, D. R., Nicholas, R. J., Maude, D. K., Utjuzh, A. N., Portal, J. C., Harris, J. J., ...
Fractional quantum Hall effect energy gaps have been measured in GaAs/GaAlAs heterojunctions as a function of Zeeman energy, which is varied by applying hydrostatic pressure up to 20 kbar. The gap at...
Karavolas, V. C., Peeters, F. M., Singleton, J., Nicholas, R. J., Herlach, F., ...
Magnetotransport properties of a pseudomorphic GaAs/Ga0.8In0.2As/Ga0.75Al0.25As heterostructure are investigated in pulsed magnetic fields up to 50 T and at temperatures of T=1.4 K and 4.2 K. The...
Pulsed Magnetic Field Measurements of the Composite Fermion Effective Mass (1995)
Leadley, D. R., Nicholas, R. J., Foxon, C. T., Harris, J. J.
Magnetotransport measurements of Composite Fermions (CF) are reported in 50 T pulsed magnetic fields. The CF effective mass is found to increase approximately linearly with the effective field $B^*$,...
Effective mass and quantum lifetime in a Si/Si0.87Ge0.13/Si two-dimensional hole gas (1994)
Whall, Terry E., Mattey, Nevil L., Plews, Andrew D., Phillips, P. J. (Peter J.), Mironov, Oleg A., Nicholas, R. J., ...
Measurements of Shubnikov de Haas oscillations in the temperature range 0.3–2 K have been used to determine an effective mass of 0.23 m0 in a Si/Si0.87Ge0.13/Si two-dimensional hole gas. This value...
Cyclotron resonance of the quasi-two-dimensional electron gas at Hg1-xCdxTe grain boundaries (1992)
Ludwig, F., Nachtwei, G., Watts, M., Bassom, N. J., Kraak, W., ...
The magnetotransmission of a p-type Hg0.766Cd0.234Te bicrystal containing a single grain boundary with an inversion layer has been investigated in the submillimetre wavelength range. For the first...
Huant, S., Hopkins, M. A., Karraï, K., Dampne, G., Nicholas, R.J., Brunel, L.C.
We present accurate measurements of 8 frequently used CW far infrared laser lines which we found substantially in error in the litterature. We also present measurements of 8 newly observed lines.
Huant, S., Hopkins, M. A., Karraï, K., Dampne, G., Nicholas, R.J., Brunel, L.C.
We present accurate measurements of 8 frequently used CW far infrared laser lines which we found substantially in error in the litterature. We also present measurements of 8 newly observed lines.
Huant, S., Hopkins, M. A., Karraï, K., Dampne, G., Nicholas, R.J., Brunel, L.C.
We present accurate measurements of 8 frequently used CW far infrared laser lines which we found substantially in error in the litterature. We also present measurements of 8 newly observed lines.