InSb Two-dimensional Electron Gas Research Articles

Gate-defined quantum point contact in an InSb two-dimensional electron gas

We investigate an electrostatically defined quantum point contact (QPC) in a high-mobility InSb two-dimensional electron gas. Well-defined conductance plateaus are observed, and the subband structure of the QPC is extracted from finite-bias measurements. The Zeeman splitting is measured in both in-plane and out-of-plane magnetic fields. We find an in-plane g factor |g∥*|≈40. The out-of-plane g factor is measured to be |g⊥*|≈50, which is close to the g factor in the bulk.Received 7 November 2020Revised 16 February 2021Accepted 11 March 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023042Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectrical conductivityQuantum transportSpin-orbit couplingPhysical SystemsQuantum wellsTwo-dimensional electron systemTechniquesCrystal growthEpitaxyEtchingEvaporationHall barLiquid helium coolingTransport techniquesk dot p methodCondensed Matter & Materials Physics

Pump-probe nuclear spin relaxation study of the quantum Hall ferromagnet at filling factor ν = 2

The nuclear spin-lattice relaxation time T1 of the ν = 2 quantum Hall ferromagnet (QHF) formed in a gate-controlled InSb two-dimensional electron gas has been characterized using a pump-probe technique. In contrast to a long T1 of quantum Hall states around ν = 1 that possesses a Korringa-type temperature dependence, the temperature-independent short T1 of the ν = 2 QHF suggests the presence of low energy collective spin excitations in a domain wall. Furthermore, T1 of this ferromagnetic state is also found to be filling- and current-independent. The interpretation of these results as compared to the T1 properties of other QHFs is discussed in terms of the domain wall skyrmion, which will lead to a better understanding of the QHF.

Quantum transport in high-quality shallow InSb quantum wells

InSb is one of the promising candidates to realize a topological state through proximity induced superconductivity in a material with strong spin–orbit interactions. In two-dimensional systems, thin barriers are needed to allow strong coupling between superconductors and semiconductors. However, it is still challenging to obtain a high-quality InSb two-dimensional electron gas in quantum wells close to the surface. Here, we report on a molecular beam epitaxy grown heterostructure of InSb quantum wells with substrate-side Si-doping and ultrathin InAlSb (5 nm, 25 nm, and 50 nm) barriers to the surface. We demonstrate that the carrier densities in these quantum wells are gate-tunable and electron mobilities up to 350 000 cm2(V s)−1 are obtained from magnetotransport measurements. Furthermore, from temperature-dependent magnetoresistance measurements, we obtain an effective mass of 0.02 m0 and find Zeeman splitting compatible with the expected band edge g-factor.

Imaging spin-resolved cyclotron trajectories in the InSb two-dimensional electron gas

We consider spin-resolved cyclotron trajectories in a magnetic focusing device with quantum point source and drain contacts defined within the InSb two-dimensional electron gas and their mapping by the scanning gate microscopy. Besides the perpendicular component of the external magnetic field which bends the electron trajectories we consider an in-plane component which introduces the spin-dependence of the cyclotron radius. We demonstrate that the focusing conductance peaks become spin-split by the in-plane magnetic field component of the order of a few tesla and that the spin-resolved trajectories can be traced separately with the conductance mapping.

Gate depletion of an InSb two-dimensional electron gas

We investigated the gate control of a two-dimensional electron gas (2DEG) confined to InSb quantum wells with an Al2O3 gate dielectric formed by atomic layer deposition on a surface layer of Al0.1In0.9Sb or InSb. The wider bandgap of Al0.1In0.9Sb compared to InSb resulted in a linear, sharp, and non-hysteretic response of the 2DEG density to gate bias in the structure with an Al0.1In0.9Sb surface layer. In contrast, a nonlinear, slow, and hysteretic (nonvolatile-memory-like) response was observed in the structure with an InSb surface layer. The 2DEG with the Al0.1In0.9Sb surface layer was completely depleted by application of a small gate voltage (∼ −0.9 V).

Thermodynamic properties of Landau levels in InSb two-dimensional electron gas

This work investigates the influence of low temperature, external magnetic field and broadened Landau levels on the thermodynamic properties of two-dimensional electron gas (2DEG) of InSb. The interplay between these two physical parameters on the magnetic field dependence of the chemical potential and the magnetization is calculated. In the absence of a complete theory that explains the Landau level broadening, experimental and theoretical studies in literature perform different model calculations of this parameter. Here it is presented that different broadening parameter of Gaussian-shaped Landau levels cause width variation in their contribution to interlevel and intralevel excitations.

Resistively detected nuclear magnetic resonance via a single InSb two-dimensional electron gas at high temperature

We report on the demonstration of the resistively detected nuclear magnetic resonance (RDNMR) of a single InSb two-dimensional electron gas (2DEG) at elevated temperatures up to 4 K. The RDNMR signal of I115n in the simplest pseudospin quantum Hall ferromagnet triggered by a large direct current shows a peak-dip line shape, where the nuclear relaxation time T1 at the peak and the dip is different but almost temperature independent. The large Zeeman, cyclotron, and exchange energy scales of the InSb 2DEG contribute to the persistence of the RDNMR signal at high temperatures.

Dynamic nuclear polarization and nuclear magnetic resonance in the simplest pseudospin quantum Hall ferromagnet

We present dynamic nuclear polarization (DNP) in the simplest pseudospin quantum Hall ferromagnet (QHF) of an InSb two-dimensional electron gas with a large g factor using tilted magnetic fields. The DNP-induced amplitude change of a resistance spike of the QHF at large current enables observation of the resistively detected nuclear magnetic resonance of the high nuclear spin isotope 115In with nine quadrupole splittings. Our results demonstrate the importance of domain structures in the DNP process. The nuclear spin relaxation time T1 in this QHF was relatively short (~ 120 s), and almost temperature independent.

A silicon metal-oxide-semiconductor field-effect transistor Hall bar for scanning Hall probe microscopy

We demonstrate successful operation of a scanning Hall probe microscope with a few micron-size resolution by using a silicon metal-oxide semiconductor field-effect transistor (Si-MOSFET) Hall bar, which is designed to improve not only the mechanical strength but also the temperature stability. The Si-MOSFET micro-Hall probe is cheaper than the current micro-Hall probes and is found to be as sensitive as a micro-Hall probe with GaAs/AlGaAs heterostructure or an epitaxial InSb two-dimensional electron gas. This was used to magnetically image the surface of a Sm(2)Co(17) permanent magnet during the magnetization reversal process as a function of an external magnetic field below 1.5 T. This revealed firm evidence of the presence of the inverse magnetic seed as theoretically predicted earlier. Magnetically pinned centers, with a typical size 80 mum, are observed to persist even under a high magnetic field, clearly indicating the robustness of the Si Hall probe against the field application as well as the repetition of the measurement.