Observation of orientation- and<i>k</i>-dependent Zeeman spin-splitting in hole quantum wires on (100)-oriented AlGaAs/GaAs heterostructures

Chen, J C H; Klochan, O.; Micolich, A. P.; Hamilton, A. R.; Martin, Theodore P.; Ho, L. H.; Zülicke, U.; Reuter, D.; Wieck, A. D.

doi:10.1088/1367-2630/12/3/033043

Cited by 35 publications

(84 citation statements)

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“…Typically it is not possible to experimentally probe the directional k-dependence of the 2D hole g-tensor, since transport measurements represent an average over all k-states at the Fermi surface. However, by using an electrostatically controlled QPC fabricated along particular in-plane directions of a 2D hole system, * Alex.Hamilton@unsw.edu.au we can perform a direct spectroscopic measurement of g * , and investigate its dependence on the magnitude and direction of the in-plane momentum [14,17,18].The device used in this work was fabricated from a (311)A-oriented heterostructure, in which a 2D hole system is induced at an AlGaAs/GaAs interface by applying a negative voltage (-0.7V) to a heavily p-doped cap layer [19]. The peak 2D hole mobility was µ = 6.0 × 10 5 cm 2 V −1 s −1 at a density p = 1.3 × 10 11 cm −2 and temperature T = 40 mK.…”

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Electrical control of the sign of thegfactor in a GaAs hole quantum point contact

et al. 2016

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Zeeman splitting of 1D hole subbands is investigated in quantum point contacts (QPCs) fabricated on a (311) oriented GaAs-AlGaAs heterostructure. Transport measurements can determine the magnitude of the g-factor, but cannot usually determine the sign. Here we use a combination of tilted fields and a unique off-diagonal element in the hole g-tensor to directly detect the sign of g * . We are able to tune not only the magnitude, but also the sign of the g-factor by electrical means, which is of interest for spintronics applications. Furthermore, we show theoretically that the resulting behaviour of g * can be explained by the momentum dependence of the spin-orbit interaction.Electrical manipulation of spin is the underlying principal of many proposed spintronic and quantum computing device architectures [1][2][3][4]. In particular, electrical control of the effective Landé g-factor in semiconductor nanostructures has been a major focus of recent research, with theoretical investigations predicting strong g * tunability in both magnitude and sign [5][6][7]. The ability to invert the sign of the g-factor and tune the system through a state of zero spin polarisation (g * = 0) could be a valuable asset in engineering solid-state spin devices [8][9][10].In this regard, quantum confined hole systems in GaAs are prime candidates due to the strong coupling between spin and orbital motion in the valence band [11]. The spin 3/2 nature of valence band holes in GaAs leads to several unique properties such as a tensor structure of g * with large anisotropy between all three spatial directions [12,13], and tunability of the g-factor across orders of magnitude [14][15][16].Previous studies of the g-factor of quantum confined holes revealed a non-monotonic dependance of |g * | on the gate bias, suggestive of a change in sign of g * [6,17]. However, these studies could not directly detect the sign of g * , only its magnitude. In this work, we utilise a novel approach to directly detect the sign of g * by exploiting a unique property of the (311) GaAs hole g-tensor, and demonstrate a gate-controlled sign change of g * in a hole quantum point contact (QPC) on (311) GaAs.We also introduce a theoretical model showing that the observed sign reversal of g * arises from the in-plane momentum dependence of the spin-orbit interaction in the valence band. Typically it is not possible to experimentally probe the directional k-dependence of the 2D hole g-tensor, since transport measurements represent an average over all k-states at the Fermi surface. However, by using an electrostatically controlled QPC fabricated along particular in-plane directions of a 2D hole system, * Alex.Hamilton@unsw.edu.au we can perform a direct spectroscopic measurement of g * , and investigate its dependence on the magnitude and direction of the in-plane momentum [14,17,18].The device used in this work was fabricated from a (311)A-oriented heterostructure, in which a 2D hole system is induced at an AlGaAs/GaAs interface by applying a negative voltage (-0.7V) to a...

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Electrical control of the sign of thegfactor in a GaAs hole quantum point contact

et al. 2016

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“…We used a heterostructure consisting of the following layers grown on a (100)-oriented substrate: 1 µm undoped GaAs, 160 nm undoped AlGaAs barrier, 10 nm undoped GaAs spacer and a 20 nm GaAs cap degenerately doped with carbon for use as a metallic gate [24,25]. A (100) heterostructure was used to avoid the crystallographic asymmetries that plague (311)A heterostructures [16,17]. Ohmic contacts are made with AuBe alloy annealed at 490 • C for 60 s. Our devices are remarkably stable, owing to population with holes electrostatically rather than by ionized modulation dopants [24,25].…”

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“…Holes in GaAs originate from p-like orbitals and behave as spin- 3 2 particles due to strong spinorbit coupling [12]. In two-and one-dimensional systems, the spin- 3 2 nature of holes leads to remarkable, highlyanisotropic phenomena [13][14][15][16][17] not observed in electron systems, and new physics is expected for hole quantum dots also [18]. Studies of Kondo physics in hole quantum dots may also provide useful connections to recent studies in bulk strongly correlated systems [19,20].…”

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Observation of the Kondo effect in a spin-32 hole quantum dot

Klochan

Micolich

Hamilton

et al. 2013

AIP Conference Proceedings

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We report the observation of Kondo physics in a spin-3 2 hole quantum dot. The dot is formed close to pinch-off in a hole quantum wire defined in an undoped AlGaAs/GaAs heterostructure. We clearly observe two distinctive hallmarks of quantum dot Kondo physics. First, the Zeeman spin-splitting of the zero-bias peak in the differential conductance is independent of gate voltage. Second, this splitting is twice as large as the splitting for the lowest one-dimensional subband. We show that the Zeeman splitting of the zero-bias peak is highly-anisotropic, and attribute this to the strong spin-orbit interaction for holes in GaAs.PACS numbers: 72.15. Qm, 75.70.Tj The observation of an unexpected minimum in the low temperature resistance of metals by de Haas in 1933 was ultimately explained thirty years later by Kondo as being due to interactions between a single magnetic impurity and the sea of conduction electrons in a metal [1,2]. More recently there has been a resurgence of interest in the Kondo effect, following the discovery that the conductance of a few electron quantum dot in the Coulomb blockade regime is enhanced when the dot contains an odd number of electrons [3][4][5]. There is a direct analogy with the Kondo effect in metals, with the localized electron in the quantum dot acting as a magnetic impurity that interacts with the two-dimensional sea of electrons in the source and drain reservoirs.Studies of the Kondo effect in bulk systems have progressed since the 1960s, with the focus shifting towards manifestations of Kondo physics in the strongly correlated electron systems formed in cuprates and heavyfermion metals [6]. More precise control via improved electrostatic gate design has similarly allowed progress towards the study of more exotic manifestations of Kondo phenomena in quantum dots such as the integer-spin [7][8][9], two-impurity [10], and orbital Kondo effects [11]. Thus far all quantum dot Kondo studies have involved electrons, and GaAs hole quantum dots present an interesting next step. Holes in GaAs originate from p-like orbitals and behave as spin-3 2 particles due to strong spinorbit coupling [12]. In two-and one-dimensional systems, the spin-3 2 nature of holes leads to remarkable, highlyanisotropic phenomena [13-17] not observed in electron systems, and new physics is expected for hole quantum dots also [18]. Studies of Kondo physics in hole quantum dots may also provide useful connections to recent studies in bulk strongly correlated systems [19,20].Here we report the observation of the Kondo effect in a GaAs hole quantum dot. Due to the poor stability of conventional gate-defined modulation doped struc- * klochan@phys.unsw.edu. A key advantage to this approach is the ability to obtain an independent estimate of the effective Landé g-factor g * . Using this we have fabricated a small hole quantum dot and conclusively demonstrate the "smoking gun" for Kondo physics [23] -a splitting of the zero-bias peak in the differential conductance that opens as 2g * µ B B in response to an in-plane...

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“…Indeed, this explains the high stability and lack of hysteresis in undoped p-type semiconductor-insulator-semiconductor field-effect transistor (SISFET) devices. 17,[77][78][79][80] There both hysteresis contributions are dealt with -the modulation doping is removed and the gate screens the surface-states. Given the success of undoped SISFETs, one might ask: Why bother making semiconductor-gated modulation-doped devices?…”

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confidence: 99%

The origin of gate hysteresis in p-type Si-doped AlGaAs/GaAs heterostructures

et al. 2012

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Gate instability/hysteresis in modulation-doped p-type AlGaAs/GaAs heterostructures impedes the development of nanoscale hole devices, which are of interest for topics from quantum computing to novel spin physics. We present an extended study conducted using custom-grown, matched modulation-doped n-type and p-type heterostructures, with/without insulated gates, aimed at understanding the origin of the hysteresis. We show the hysteresis is not due to the inherent 'leakiness' of gates on p-type heterostructures, as commonly believed. Instead, hysteresis arises from a combination of GaAs surface-state trapping and charge migration in the doping layer. Our results provide insights into the physics of Si acceptors in AlGaAs/GaAs heterostructures, including widely-debated acceptor complexes such as Si-X. We propose methods for mitigating the gate hysteresis, including poisoning the modulation-doping layer with deep-trapping centers (e.g., by co-doping with transition metal species), and replacing the Schottky gates with degenerately-doped semiconductor gates to screen the conducting channel from GaAs surface-states.

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Observation of orientation- andk-dependent Zeeman spin-splitting in hole quantum wires on (100)-oriented AlGaAs/GaAs heterostructures

Cited by 35 publications

References 32 publications

Electrical control of the sign of thegfactor in a GaAs hole quantum point contact

Electrical control of the sign of thegfactor in a GaAs hole quantum point contact

Observation of the Kondo effect in a spin-32 hole quantum dot

The origin of gate hysteresis in p-type Si-doped AlGaAs/GaAs heterostructures

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