Two-dimensional electron-hole system in a HgTe-based quantum well

Квон, З. Д.; Olshanetsky, E. B.; Козлов, Д. А.; Михайлов, Н. Н.; Дворецкий, С. А.

doi:10.1134/s0021364008090117

Cited by 104 publications

(96 citation statements)

References 7 publications

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“…This dependence essentially differs from the classical N-shaped Hall resistivity expected for electron-hole systems. 7,10 A theoretical consideration based on calculation of the Landau level spectrum for our structure qualitatively explains the main features of our observations and helps us to uncover a mechanism of transition to the σ xy = 0 state in the systems under investigation.…”

Section: Introductionmentioning

confidence: 98%

“…The densities of carriers in these wells are considerably smaller those those for the [013]-, [112]-, and slightly wider [001]-grown wells examined previously in our experiments. 7,10,12,13 For this reason, we see quantum features in transport at smaller magnetic fields. Apart from the existence of the σ xy = 0 plateau in the dependence of Hall conductivity on the gate voltage, we have found an unusual nonmonotonic dependence of the Hall resistivity ρ yx on the magnetic field.…”

Section: Introductionmentioning

confidence: 98%

“…The wide CdHgTe/HgTe/CdHgTe quantum wells, where separation of the size-quantized subbands is relatively small, are of particular interest in this connection. 7 The 2D conduction (c) band in such systems is formed from the first heavy-hole subband (h1) whose effective mass is positive, 8 while the second heavy-hole subband (h2) forms the upper part of the 2D valence (v) band. Owing to a uniaxial strain of the HgTe layer, which is caused by the lattice mismatch of HgTe and CdTe 9 or CdHgTe, 10 the energy spectrum of the h2 subband is essentially nonmonotonic and has maxima away from the point of the 2D Brillouin zone.…”

Section: Introductionmentioning

confidence: 99%

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Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

Raichev¹,

Gusev

Olshanetsky

et al. 2012

Phys. Rev. B

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The transport properties of the two-dimensional system in HgTe-based quantum wells containing simultaneously electrons and holes of low densities are examined. The Hall resistance, as a function of perpendicular magnetic field, reveals an unconventional behavior, different from the classical Nshaped dependence typical for bipolar systems with electron-hole asymmetry. The quantum features of magnetotransport are explained by means of numerical calculation of Landau level spectrum based on Kane Hamiltonian. The origin of the quantum Hall plateau σxx = 0 near the charge neutrality point is attributed to special features of Landau quantization in our system.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

Raichev¹,

Gusev

Olshanetsky

et al. 2012

Phys. Rev. B

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“…Examples are given in the Supplemental Material [18]. A similar analysis to extract the densities and mobilities of the two carriers has been employed previously in semimetallic HgTe quantum wells [20]. At V g ≥ 2 V, the nonlinear Hall effect turns into an essentially linear dependence of ρ xy ðBÞ indicating that the current is carried by only one sort of carrier, i.e., surface electrons.…”

mentioning

confidence: 99%

“…[16]), holes and Dirac electrons coexist. The coexistence of two types of charge carriers is experimentally supported by a large positive magnetoresistance ρ xx ðBÞ and by a nonlinear ρ xy ðBÞ, typical for electron-hole systems [19,20]. To estimate the mobility and density of the coexisting electron and holes, we used the Drude formalism for two types of carriers.…”

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confidence: 99%

Transport Properties of a 3D Topological Insulator based on a Strained High-Mobility HgTe Film

et al. 2014

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We investigate the magnetotransport properties of strained 80 nm thick HgTe layers featuring a high mobility of μ ∼ 4 × 10 5 cm 2 =V · s. By means of a top gate, the Fermi energy is tuned from the valence band through the Dirac-type surface states into the conduction band. Magnetotransport measurements allow us to disentangle the different contributions of conduction band electrons, holes, and Dirac electrons to the conductivity. The results are in line with previous claims that strained HgTe is a topological insulator with a bulk gap of ≈ 15 meV and gapless surface states. DOI: 10.1103/PhysRevLett.112.196801 PACS numbers: 73.25.+i, 05.60.Gg, 73.20.At, 73.43.-f The discovery of two-(2D) and three-dimensional (3D) topological insulators (TIs), a new material class with insulating bulk and topologically protected conducting surface states, has opened an exciting research field in condensed matter physics [1][2][3][4][5][6][7][8][9][10]. Although quite a number of different, especially, Bi-based materials [11][12][13][14], belong to this category, materials which combine high charge carrier mobility and insulating bulk are still scarce. This is mostly due to the fact that Bi-based 3D TIs are heavily doped alloy films with a low mobility ≈1000 cm 2 =V · s and a high bulk carrier density of 10 17 -10 19 cm −3 . HgTe-based 2D TIs, on the other hand, are characterized by very high mobilities enabling the discovery of the quantum spin Hall effect [15]. A recent analysis of the sequence of quantum Hall plateaus suggests that also strained HgTe layers constitute a 3D TI. The strain opens a gap in the gapless semimetal HgTe so that the TI properties can be explored by tuning the Fermi energy E F into the bulk gap and probing the transport properties of the gapless surface states. Although the strained HgTe film has a much higher mobility μ ¼ ð3 − 4Þ × 10 4 cm 2 =V · s, the high bulk carrier density and the absence of a top gate have complicated the detection of 3D TIs so far [16,17].The strain in HgTe layers grown by molecular beam epitaxy stems from a 0.3% lattice mismatch between HgTe and CdTe. The corresponding critical film thickness is larger than 100 nm, meaning that thinner films adopt the substrate lattice constant. Because of this strain, a small gap of ∼15 meV opens (see below) in the bulk energy spectrum of the film. Within the bulk gap, the gapless surface states reside. The charge neutrality point of the corresponding Dirac cone is located in the valence band [16].In this Letter, we report on transport properties of highmobility, 80 nm wide, strained HgTe films equipped with a gate. The low disorder manifested in high charge carrier mobilities, together with the possibility to tune E F from the valence via the gap into the conduction band, enables us to probe the 2D Dirac surface states when E F is in the bulk energy gap. Since HgTe films grown on CdTe suffer from dislocations due to the lattice mismatch, our 80 nm thick HgTe films were separated from the CdTe substrate by a 20 nm thin Cd 0.7 Hg 0.3 Te buf...

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Terahertz Magnetospectroscopy of Cyclotron Resonances from Topological Surface States in Thick Films of Cd_xHg_1−xTe

Otteneder¹,

Sacré²,

Yahniuk³

et al. 2020

Physica Status Solidi (b)

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Herein, studies of the cyclotron resonance (CR) in thick films with different cadmium contents corresponding to materials with and without band inversion, as well as critical content corresponding to an almost linear energy dispersion are presented. The results demonstrate that the formation of 2D topological surface states requires sharp interfaces between layers with and without band inversion, in which case the corresponding CR is clearly observed for the out‐of‐plane orientation of magnetic field but does not show up for an in‐plane orientation. In contrast, all samples having more conventional technological design with smooth interfaces (i.e., containing regions of with gradually changing Cd content x) show equally pronounced CR in both in‐plane and out‐of‐plane magnetic field revealing that CR is excited in effectively 3D states. Modeling of the surface states for different film designs supports main observations. In all samples, additional broad helicity‐independent resonances are observed, which are attributed to photoionization and magnetic freeze‐out of impurity states.

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Two-dimensional electron-hole system in a HgTe-based quantum well

Cited by 104 publications

References 7 publications

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

Transport Properties of a 3D Topological Insulator based on a Strained High-Mobility HgTe Film

Terahertz Magnetospectroscopy of Cyclotron Resonances from Topological Surface States in Thick Films of Cd_xHg_1−xTe

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Two-dimensional electron-hole system in a HgTe-based quantum well

Cited by 104 publications

References 7 publications

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

Unconventional Hall effect near charge neutrality point in a two-dimensional electron-hole system

Transport Properties of a 3D Topological Insulator based on a Strained High-Mobility HgTe Film

Terahertz Magnetospectroscopy of Cyclotron Resonances from Topological Surface States in Thick Films of CdxHg1−xTe

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Terahertz Magnetospectroscopy of Cyclotron Resonances from Topological Surface States in Thick Films of Cd_xHg_1−xTe