Temperature-Induced Topological Phase Transition in HgTe Quantum Wells

Kadykov, A. M.; Криштопенко, С. С.; Jouault, Benoît; Desrat, Wilfried; Knap, W.; Ruffenach, Sandra; Conséjo, Christophe; Torres, J.; Morozov, S. V.; Михайлов, Н. Н.; Dvoretskii, S. A.; Теппе, Ф.

doi:10.1103/physrevlett.120.086401

Cited by 52 publications

(47 citation statements)

References 33 publications

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“…In this work, we propose a minimal effective 2D model, which describes the side maxima in the valence subband and qualitatively reproduces the band structure calculations based on the Kane Hamiltonian, which validity is confirmed by a large variety of experiments performed by different techniques [2][3][4]6,[25][26][27][28][29][30][31][32][33] . By using the derived 2D Hamiltonian, we explore a picture of the edge states in HgTe-based QSHIs with direct and indirect band gap.…”

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confidence: 61%

Realistic picture of helical edge states in HgTe quantum wells

Криштопенко

Теппе

2018

Phys. Rev. B

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We propose a minimal effective two-dimensional Hamiltonian for HgTe/CdHgTe quantum wells (QWs) describing the side maxima of the first valence subband. By using the Hamiltonian, we explore the picture of helical edge states in tensile and compressively strained HgTe QWs. We show that both dispersion and probability density of the edge states can differ significantly from those predicted by the Bernevig-Hughes-Zhang (BHZ) model. Our results pave the way towards further theoretical investigations of HgTe-based quantum spin Hall insulators with direct and indirect band gaps beyond the BHZ model.The inverted HgTe/CdHgTe quantum well (QW) is the first two-dimensional (2D) system, in which a quantum spin Hall insulator (QSHI) state was theoretically predicted 1 and then experimentally observed 2-4 . The origin of the topologically nontrivial QSHI state is caused by inverted band structure of bulk HgTe, which leads to a peculiar confinement effect in HgTe/CdHgTe QWs. Specifically, in narrow QWs, the first electron-like subband E 1 lies above the first hole-like level H 1, and the system is characterized by normal band ordering with trivial insulator state. As the QW width d is varied (see Fig. 1a), the E 1 and H 1 subbands are crossed 5 , and the band structure mimics a linear dispersion of massless Dirac fermions 6 . When d exceeds the critical width d c , an inversion of the E 1 and H 1 levels drives the system in QSHI state with a pair of gapless helical edge states topologically protected due to time-reversal symmetry 1 .So far, theoretical description of the phase transition between trivial and QSHI states in HgTe QWs has been based on the Bernevig-Hughes-Zhang (BHZ) 2D model 1 . The latter is derived from the Kane Hamiltonian 7 , which includes Γ 6 , Γ 8 , Γ 7 bulk bands with the confinement effect. Within the representation defined by the basis states |E 1,+ , |H 1,+ , |E 1,-, |H 1,-, the effective 2D Hamiltonian has the form:

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confidence: 61%

Realistic picture of helical edge states in HgTe quantum wells

Криштопенко

Теппе

2018

Phys. Rev. B

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“…This feature has recently been explored to trace topological phase transition as a function of temperature. 44 6.5 nm QW in a magnetic field Based on results presented above, we conclude that HgTe QWs with the smallest possible B c should be engineered to decrease or avoid topological edge states perturbing the precision of the QHE. Figure 5 shows the band structure of sample S3.…”

Section: Contribution Of the Ti States In Qhe Measurementsmentioning

confidence: 63%

“…The cian region is the only one accessible for both permanent magnets and liquid helium systems effects due to lattice constant mismatch, with the parameters confirmed by our earlier investigations. 44,45 According to the calculation results presented in Fig. 3, sample S1 has an inverted band structure up to the critical magnetic field B c ≈ 4 T, at which a crossing of the highest LL from the valence band with the lowest LL from the conduction band occurs.…”

Section: Contribution Of the Ti States In Qhe Measurementsmentioning

confidence: 92%

Magneto-transport in inverted HgTe quantum wells

Yahniuk¹,

Криштопенко²,

Grabecki³

et al. 2019

npj Quantum Mater.

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HgTe quantum wells (QWs) are two-dimensional semiconductor systems that change their properties at the critical thickness d c , corresponding to the band inversion and topological phase transition. The motivation of this work was to study magnetotransport properties of HgTe QWs with thickness approaching d c , and examine them as potential candidates for quantum Hall effect (QHE) resistance standards. We show that in the case of d > d c (inverted QWs), the quantization is influenced by coexistence of topological helical edge states and QHE chiral states. However, at d ≈ d c , where QW states exhibit a graphene-like band structure, an accurate Hall resistance quantization in low magnetic fields (B ≤ 1.4 T) and at relatively high temperatures (T ≥ 1.3 K) may be achieved. We observe wider and more robust quantized QHE plateaus for holes, which suggests-in accordance with the "charge reservoir" model-a pinning of the Fermi level in the valence band region. Our analysis exhibits advantages and drawbacks of HgTe QWs for quantum metrology applications, as compared to graphene and GaAs counterparts.

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“…Mercury cadmium telluride has been studied for more than 50 years now, but only recently there have been fabricated crystals of a high enough quality to reveal fascinating phenomena like observation of the Dirac fermions in bulk crystals [1,2] and topological transitions in quantum wells [3]. Thus, a very well known material which has been used during last decades for fabrication of lowenergy photons' detectors, has appeared now to serve for a new type of research.…”

Section: Introductionmentioning

confidence: 99%

Magnetoconductivity of a Mercury Cadmium Telluride Resonant THz Detector

et al. 2018

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Magnetoconductivity tensorσ of a THz detector made of a Hg1−xCdxTe epitaxial layer was determined at a few temperatures T between 2 K and 100 K for magnetic fields B up to 0.5 T. At all temperatures the sample exhibited n-type conductivity. The observed dependence ofσ(B) could be reasonably approximated with a onecarrier model at the highest T , but this model cannot be used to describe data at the lowest temperatures. We show that optical transitions at THz frequencies occur at magnetic fields characterized by strong changes of conductivity. That is why response of the detector working in a photoconductive mode must be corrected by taking into account itsσ(B) dependence.

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Temperature-Induced Topological Phase Transition in HgTe Quantum Wells

Cited by 52 publications

References 33 publications

Realistic picture of helical edge states in HgTe quantum wells

Realistic picture of helical edge states in HgTe quantum wells

Magneto-transport in inverted HgTe quantum wells

Magnetoconductivity of a Mercury Cadmium Telluride Resonant THz Detector

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