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

Raichev, O. É.; Gusev, G. M.; Olshanetsky, E. B.; Kvon, Z. D.; Михайлов, Н. Н.; Dvoretsky, S. A.; Portal, J. C.

doi:10.1103/physrevb.86.155320

Cited by 18 publications

(17 citation statements)

References 19 publications

(51 reference statements)

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“…The reentrant sign-alternating behavior of ρ xy (B) has been revealed in a single HgTe QW in Ref. 12 at much lower fields of several Tesla, and a value of the band overlap in their sample was estimated as of the order of 1 meV. Much higher fields of the ρ xy (B) sign reversal in our DQW structures indicate much larger overlaps and much higher values of characteristic fields for the level crossings.…”

Section: Discussion Of the Resultssupporting

confidence: 67%

Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

Yakunin¹,

Суслов²,

Popov³

et al. 2016

Phys. Rev. B

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We present the first experimental study of the double-quantum-well (DQW) system made of 2D layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage Vg. This large overlap manifests itself in a much higher critical field Bc separating the range above it with a plain behavior of the Hall magnetoresistance ρxy(B), where the quantum peculiarities shift linearly with Vg, and the range below with a complicated behavior. In the latter case specific structures in ρxy(B) are formed like a double-N -shaped ρxy(B), reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative Vg as revealed (i) from fits to the low-field N -shaped ρxy(B), (ii) from the Fourier analysis of oscillations in ρxx(B) and (iii) from a specific behavior of ρxy(B) at high positive Vg. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated Vg while the hole density p drops down from the value a factor of 6 larger than n at extreme negative Vg to almost zero at extreme positive Vg passing through the charge neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an oscillating behavior of the valence subband top versus field due to lateral maxima in the energy spectrum, (ii) a reduced gap between the lowest electron and the highest hole magnetic levels where the electron-and hole-type localized states are superposed, and (iii) a possible formation of the interlayer electron-hole excitons.

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Section: Discussion Of the Resultssupporting

confidence: 67%

Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

Yakunin¹,

Суслов²,

Popov³

et al. 2016

Phys. Rev. B

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“…The shape of the lower part of the Dirac cone and its relative position to the Γ 8 hh states gives an opportunity for the experimental investigation of this TSS part as it is also for the strained 2D system. As shown by the other authors the theoretical and experimental investigation of both upper and lower part of the Dirac cones in case of the HgTe QW provides a lot of interesting results [44][45][46][47][48]. The 2D and 3D strained structures with the TSS dispersion relation similar to that obtained for HgTe QW should be a very interesting experimental object for further verification of all these effects.…”

Section: Discussionsupporting

confidence: 56%

Formation Dirac point and the topological surface states for HgCdTe-QW and mixed 3D HgCdTe TI

Marchewka

2016

EPJ Web Conf.

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Abstract. In this paper the results of numerical calculations based on the finite difference method (FDM) for the 2D and 3D TI with and without uniaxial tensile strain for mixed Hg 1-x Cd x Te structures are presented. The numerical calculations were made using the 8x8 model for x from 0 up to 0.155 and for the wide range for the thickness from a few nm for 2D up to 150 nm for 3D TI as well as for different mismatch of the lattice constant and different barrier potential in the case of the QW. For the investigated region of the Cd composition (x value) the negative energy gap (E g =* 8 -* 6 ) in the Hg 1-x Cd x Te is smaller than in the case of pure HgTe which, as it turns out, has a significant influence on the topological surface states (TSS) and the position of the Dirac point for QW as well as for 3D TI. The results show that the strained gap and the position of the Dirac point against the * 8 is a function of the x-Cd compounds in the case of the 3D TI as well as the critical width of the mixed Hg 1-x Cd x Te QW.

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“…The material parameters used for these calculations are given in Ref. 13 Figure 7 demonstrates the effect of magnetic field below the point of phase transition. Three subbands (e, h1, and h2) are spin-degenerate at B = 0, since the well is symmetric.…”

Section: Theorymentioning

confidence: 99%

“…The ordinary 2D insulator state is realized at small well widths (approximately, up to 6.3 nm), while 2D topological insulator (QSHE) state exists at larger well widths. The large-width (20 nm and wider) quantum wells support semimetallic 2D state [11][12][13] with overlapped conduction and valence 2D bands. Recent theoretical consideration 14 suggests one more possibility, when application of a strong (of the order 10 T) magnetic field parallel to the plane of HgTe quantum well in QSHE state rebuilds the subband structure and creates a gapless 2D state with electron energy spectrum similar to that of bulk HgTe.…”

Section: Introductionmentioning

confidence: 99%

Transition from insulating to metallic phase induced by in-plane magnetic field in HgTe quantum wells

et al. 2013

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We report transport measurements in HgTe-based quantum wells with well width of 8 nm, corresponding to quantum spin Hall state, subject to in-plane magnetic field. In the absence of the magnetic field the local and nonlocal resistances behave very similar, which confirms the edge state transport in our system. In the magnetic field, we observe a monotonic decrease of the resistance with saturation of local resistance, while nonlocal resistance disappears completely, independent of the gate voltage. We believe that these evidences of metallic behavior indicate a transition to a gapless two-dimensional phase, according to theoretical predictions. The influence of disorder on resistivity properties of HgTe quantum wells under in-plane magnetic field is discussed.

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

Cited by 18 publications

References 19 publications

Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

Formation Dirac point and the topological surface states for HgCdTe-QW and mixed 3D HgCdTe TI

Transition from insulating to metallic phase induced by in-plane magnetic field in HgTe quantum wells

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