Publications (27)
On the Zero-Bias Anomaly in Quantum Wires
S. Sarkozy, F. Sfigakis, K. Das Gupta +4
Undoped GaAs/AlGaAs heterostructures have been used to fabricate quantum wires in which the average impurity separation is greater than the device size. We compare the behavior of…
Pulsed Electroluminescence in a Dopant-free Gateable Semiconductor
S. R. Harrigan, F. Sfigakis, L. Tian +7
We report on a stable form of pulsed electroluminescence in a dopant-free direct bandgap semiconductor heterostructure which we coin the tidal effect. Swapping an inducing gate vol…
Observation of an Abrupt 3D-2D Morphological Transition in Thin Al Layers Grown by MBE on InGaAs surface
A. Elbaroudy, B. Khromets, F. Sfigakis +7
Among superconductor/semiconductor hybrid structures, in-situ aluminum (Al) grown on InGaAs/InAs is widely pursued for the experimental realization of Majorana Zero Mode quasiparti…
Microwave spectroscopy of a carbon nanotube charge qubit
Z. V. Penfold-Fitch, F. Sfigakis, M. R. Buitelaar
Carbon nanotube quantum dots allow accurate control of electron charge, spin and valley degrees of freedom in a material which is atomically perfect and can be grown isotopically p…
Distinguishing impurity concentrations in GaAs and AlGaAs, using very shallow undoped heterostructures
W. Y. Mak, K. Das Gupta, H. E. Beere +3
We demonstrate a method of making a very shallow, gateable, undoped 2-dimensional electron gas. We have developed a method of making very low resistivity contacts to these structur…
Dependence of the 0.7 anomaly on the curvature of the potential barrier in quantum wires
L. W. Smith, H. Al-Taie, A. A. J. Lesage +9
Ninety eight one-dimensional channels defined using split gates fabricated on a GaAs/AlGaAs heterostructure are measured during one cooldown at 1.4 K. The devices are arranged in a…
Orientation of hole quantum Hall nematic phases in an out-of-plane electric field
A. F. Croxall, F. Sfigakis, J. Waldie +2
We present observations of an anisotropic resistance state at Landau level filling factor in a two-dimensional hole system (2DHS), which occurs for certain values of hole…
Non-adiabatic single-electron pump in a dopant-free GaAs/AlGaAs 2DEG
B. Buonacorsi, F. Sfigakis, A. Shetty +7
We have realized quantized charge pumping using non-adiabatic single-electron pumps in dopant-free GaAs two-dimensional electron gases (2DEGs). The dopant-free III-V platform allow…
Magnetotransport Spectroscopy of Strongly Rashba-Split Hole Subbands Reveals Many-Body Interactions
F. Sfigakis, N. A. Cockton, M. Korkusinski +13
We report the results of magnetotransport experiments carried out on low-disorder 2D hole gases (2DHG) in the strongly correlated liquid regime, hosted in dopant-free (100) GaAs/Al…
Electroluminescence in dopant-free GaAs/AlGaAs single heterojunctions: 2D free excitons, H-band, and the tidal effect
N. Sherlekar, S. R. Harrigan, L. Tian +9
Bright electroluminescence (EL) from dopant-free ambipolar lateral p-n junctions in GaAs/AlGaAs single heterointerface (SH) heterostructures is used to probe neutral free excitons…
All-electric all-semiconductor spin field effect transistors
Pojen Chuang, Sheng-Chin Ho, L. W. Smith +10
The spin field effect transistor envisioned by Datta and Das opens a gateway to spin information processing. Although the coherent manipulation of electron spins in semiconductors…
Effects of biased and unbiased illuminations on dopant-free GaAs/AlGaAs 2DEGs
A. Shetty, F. Sfigakis, W. Y. Mak +16
Illumination is performed at low temperature on dopant-free two-dimensional electron gases (2DEGs) of varying depths, under unbiased (gates grounded) and biased (gates at a positiv…
Vortex detection and quantum transport in mesoscopic graphene Josephson junction arrays
C. L. Richardson, S. D. Edkins, G. R. Berdiyorov +9
We investigate mesoscopic Josephson junction arrays created by patterning superconducting disks on monolayer graphene, concentrating on the high- regime of these devices and…
Switching between attractive and repulsive Coulomb-interaction-mediated drag in an ambipolar GaAs/AlGaAs bilayer device
B. Zheng, A. F. Croxall, J. Waldie +5
We present measurements of Coulomb drag in an ambipolar GaAs/AlGaAs double quantum well structure that can be configured as both an electron-hole bilayer and a hole-hole bilayer, w…
Landau level spin diode in a GaAs two dimensional hole system
O. Klochan, A. R. Hamilton, K. das Gupta +3
We have fabricated and characterized the Landau level spin diode in GaAs two dimensional hole system. We used the hole Landau level spin diode to probe the hyperfine coupling betwe…
Ultra-shallow quantum dots in an undoped GaAs/AlGaAs 2D electron gas
W. Y. Mak, F. Sfigakis, K. Das Gupta +7
We report quantum dots fabricated on very shallow 2-dimensional electron gases, only 30 nm below the surface, in undoped GaAs/AlGaAs heterostructures grown by molecular beam epitax…
Fabrication and characterisation of ambipolar devices on an undoped AlGaAs/GaAs heterostructure
J. C. H. Chen, D. Q. Wang, O. Klochan +7
We have fabricated AlGaAs/GaAs heterostructure devices in which the conduction channel can be populated with either electrons or holes simply by changing the polarity of a gate bia…
Kondo physics versus spin gap physics in fully spin-split quantum wires
F. Sfigakis, C. J. B. Ford, M. Pepper +4
Linear and nonlinear transport of quantum wires is investigated at a magnetic field where spin-split one-dimensional (1D) subbands are equidistant in energy. In this seldom-studied…
Statistical study of conductance properties in one-dimensional quantum wires focussing on the 0.7 anomaly
L. W. Smith, H. Al-Taie, F. Sfigakis +9
The properties of conductance in one-dimensional (1D) quantum wires are statistically investigated using an array of 256 lithographically-identical split gates, fabricated on a GaA…
Evidence of Novel Quasiparticles in a Strongly Interacting Two-Dimensional Electron System: Giant Thermopower and Metallic Behaviour
Vijay Narayan, M. Pepper, J. Griffths +5
We report thermopower () and electrical resistivity () measurements in low-density (10 m), mesoscopic two-dimensional electron systems (2DESs) in GaAs/A…
Linear non-hysteretic gating of a very high density 2DEG in an undoped metal-semiconductor-metal sandwich structure
K. Das Gupta, A. F. Croxall, W. Y. Mak +5
Modulation doped GaAs-AlGaAs quantum well based structures are usually used to achieve very high mobility 2-dimensional electron (or hole) gases. Usually high mobilities ($>10^{7}{…
Enhanced effective masses, spin-orbit polarization, and dispersion relations in 2D hole gases under strongly asymmetric confinement
N. A. Cockton, F. Sfigakis, M. Korkusinski +13
The dispersion of Rashba-split heavy-hole subbands in GaAs two-dimensional hole gases (2DHGs) is difficult to access experimentally because strong heavy-hole-light-hole mixing prod…
Hybrid Epitaxial Al/InGaAs system: Solid-state dewetting and Al facet formation
A. Elbaroudy, N. Shaw, Sandra J. Gibson +4
Hybrid superconductor--semiconductor platforms can host subgap electronic excitations such as Andreev bound states (ABSs); in topological regimes, a special zero-energy class, Majo…
The effect of split gate size on the electrostatic potential and 0.7 anomaly within one-dimensional quantum wires on a modulation doped GaAs/AlGaAs heterostructure
L. W. Smith, H. Al-Taie, A. A. J. Lesage +9
We study 95 split gates of different size on a single chip using a multiplexing technique. Each split gate defines a one-dimensional channel on a modulation-doped GaAs/AlGaAs heter…
High transparency induced superconductivity in field effect two-dimensional electron gases in undoped InAs/AlGaSb surface quantum wells
E. Annelise Bergeron, F. Sfigakis, A. Elbaroudy +7
We report on transport characteristics of field effect two-dimensional electron gases (2DEG) in 24 nm wide indium arsenide surface quantum wells. High quality single-subband magnet…
Field effect two-dimensional electron gases in modulation-doped InSb surface quantum wells
E. Annelise Bergeron, F. Sfigakis, Y. Shi +6
We report on transport characteristics of field effect two-dimensional electron gases (2DEG) in surface indium antimonide quantum wells. The topmost 5 nm of the 30 nm wide quantum…
Surface-acoustic-wave-driven luminescence from a lateral p-n junction
J. R. Gell, P. Atkinson, S. P. Bremner +9
The authors report surface-acoustic-wave-driven luminescence from a lateral p-n junction formed by molecular beam epitaxy regrowth of a modulation doped GaAs/AlGaAs quantum well on…