Evidence for localization and 0.7 anomaly in hole quantum point contacts

Komijani, Yashar; Csontos, Miklós; Shorubalko, Ivan; Ihn, Thomas; Ensslin, Klaus; Meir, Yigal; Reuter, D.; Wieck, A. D.

doi:10.1209/0295-5075/91/67010

Cited by 28 publications

(59 citation statements)

References 36 publications

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“…In this sense the present case appears more clear cut as ZBA appears to be less of an issue in the nonlinear, biased regime and/or at elevated temperatures (see, e.g., Ref. 13 for some recent experimental data).…”

Section: Introductionmentioning

confidence: 56%

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Electric-field control of magnetization in biased semiconductor quantum wires and point contacts

2011

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The true origin of the 0.25 and 0.85 conductance features which have been observed in biased split-gate quantum wires and quantum point contacts in semiconductor heterostructures is debated in the literature; one suggestion is that they are caused by spontaneous spin polarization due to the electron-electron interactions. The present work confirms that spontaneous spin splitting may occur within the system and is responsible for both the 0.25 and 0.85 plateaux. We have also shown that the 0.25 plateau consists of two regions, one that is spin polarized, and one that is degenerate with a conductance that remains essentially the same at both sides of the transition. This finding could be of interest for semiconductor spintronics because it opens the possibility for spin manipulation by electric means only.

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Section: Introductionmentioning

confidence: 56%

“…12, as well as some recent developments including also effects of spin-orbit interactions and localization (Refs. [13][14][15][16][17][18][19], and references within).…”

Section: Introductionmentioning

confidence: 99%

Electric-field control of magnetization in biased semiconductor quantum wires and point contacts

2011

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“…cases, plateaus at e 2 /h and 3e 2 /h emerge, indicating the onset of spin-splitting [28], accompanied by sharp resonances signalling formation of a bound-state within the wire [22,[29][30][31]. We will show later in Fig.…”

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confidence: 75%

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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“…Furthermore, holes in GaAs have a theoretically predicted effective mass several times larger than electrons in the conduction band. The smaller Fermi energy makes the carrier-carrier Coulomb interactions more relevant, allowing the study of manybody related effects [10,11,14].The strong SO-splitting in 2DHGs can be observed from the presence of a beating in the low-field Shubnikovde Haas (SdH) oscillations [18][19][20][21][22][23]. In an approximate picture, the beating is due to the presence of different sets of SdH oscillations for the two angular momentum eigenstates (referred to as 1 and 2), that contribute to transport in parallel.…”

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confidence: 99%

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Spin-orbit splitting and effective masses inp-type GaAs two-dimensional hole gases

et al. 2014

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We present magnetotransport measurements performed on two-dimensional hole gases embedded in carbon doped p-type GaAs/AlGaAs heterostructures grown on [001] oriented substrates. A pronounced beating pattern in the Shubnikov-de Haas oscillations proves the presence of strong spin-orbit interaction in the device under study. We estimate the effective masses of spin-orbit split subbands by measuring the temperature dependence of the Shubnikov-de Haas oscillations at different hole densities. While the lighter heavy-hole effective mass is not energy dependent, the heavier heavy-hole effective mass has a prominent energy dependence, indicating a strong spinorbit induced non parabolicity of the valence band. The measured effective masses show qualitative agreement with self-consistent numerical calculations.The understanding of any semiconductor material starts with the knowledge of the carriers effective mass and its energy dependence. For the most important semiconductors, such as Si and GaAs, the electron effective mass has been widely investigated using temperature dependent transport and cyclotron resonance experiments [1][2][3][4][5][6][7]. For two-dimensional hole gases (2DHG) in GaAs the situation is significantly more complicated. Despite the importance of GaAs for fundamental research and technological applications, a detailed study of the effective mass of holes in GaAs 2DHG grown along the high symmetry [001] direction remains to be done. The interpretation of the rapidly increasing number of experiments performed in 2DHGs requires a solid understanding of the physics underlying the effective mass value and its dependence on quantities such as hole density and spinorbit interaction (SOI) strength.Holes in the valence band of GaAs are characterized by wave functions whose symmetry in real space is reminiscent of atomic p-orbitals. Due to the interplay of the non-zero orbital angular momentum, bulk SOI and confinement in growth direction, the carriers in 2DHGs are effectively described as heavy holes with total angular momentum z component ±3/2, for which SOI corrections are expected to be stronger than for their spin-1/2 electronic counterparts. SOI breaks ±3/2 total angular momentum degeneracy already at zero magnetic field, resulting in a band-warping. Accordingly, spin and momentum eigenstates mix, leading to a profound difference between the two spin-orbit-split (SO-split) bands [8]. In p-type 2DHG, the main contribution to SOI is of Rashba type and originates from the structure inversion asymmetry of the host heterostrucure. Unlike the case of electrons, Rashba SOI for holes is expected to have a cubic dependence on the in-plane momentum [9]. With respect to other materials, GaAs 2DHGs offer the unique opportunity to study pronounced SOI effects in a system that can be grown with high control [10,11] and reliably processed into nanostructures [12][13][14][15][16][17]. Furthermore, holes in GaAs have a theoretically predicted effective mass several times larger than electrons in the conduction band. The...

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Evidence for localization and 0.7 anomaly in hole quantum point contacts

Cited by 28 publications

References 36 publications

Electric-field control of magnetization in biased semiconductor quantum wires and point contacts

Electric-field control of magnetization in biased semiconductor quantum wires and point contacts

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

Spin-orbit splitting and effective masses inp-type GaAs two-dimensional hole gases

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