Inapplicability of Martin transformation to elastic constants of zinc-blende and wurtzite group-III nitride alloys

Łepkowski, S. P.

doi:10.1063/1.4914416

Cited by 17 publications

(8 citation statements)

References 31 publications

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“…The second-order elastic constants and the third-order elastic constants (assuming linear dependence on composition in InGaN) are taken from ref. 43 and ref. 14 , respectively.…”

Section: Methodsmentioning

confidence: 86%

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Łepkowski

Bardyszewski

2018

Sci Rep

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We study the influence of negative spin-orbit coupling on the topological phase transition and properties of the topological insulator state in InGaN-based quantum wells grown along c axis of the wurtzite lattice. The realistic eight-band k·p method with relativistic and nonrelativistic linear-k terms is employed. Our calculations show that the negative spin-orbit coupling in InN is not an obstacle to obtain the topological insulator phase in InN/InGaN and InGaN/GaN quantum wells. The bulk energy gap in the topological insulator state can reach 2 meV, which allows experimental verification of the edge state transport in these materials. The topological phase transition occurs due to the band inversion between the highest light hole subband and the lowest conduction subband, and almost always is mediated by the two-dimensional Weyl semimetal, arising from an anticrossing of these subbands at zero in-plane wave vector. However, for certain InGaN/GaN quantum wells, we find that the magnitude of this anticrossing vanishes, leading to the appearance of the Dirac semimetal. The novel transition between the Weyl and Dirac semimetals originates from vanishing of the average in-plane spin-orbit interaction parameter, which decouples the conduction subband from the light hole subband at zero in-plane wave vector.

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“…The second-order elastic constants and the third-order elastic constants (assuming linear dependence on composition in InGaN) are taken from ref. 43 and ref. 14 , respectively.…”

Section: Methodsmentioning

confidence: 86%

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Łepkowski

Bardyszewski

2018

Sci Rep

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“…Similarly to the case of InN/GaN MQWs, L b is equal to 40 nm. The solid line in figure 12 corresponds to the critical In content of In x Ga 1−x N/GaN QWs, x c , which allows for pseudomorphic growth without strain relaxation, according to the Fischer-Küchne-Richter model [50], with the elastic constants for In x Ga 1−x N taken from [32]. For the In content larger than x c , strain in the system will be relaxed through the formation of dislocations.…”

Section: Resultsmentioning

confidence: 99%

“…In order to apply the model presented above, we have to specify the material parameters for GaN, InN and In x Ga 1−x N. The values of P sp , e ij , and B ijk were determined in [25] using ab initio calculations in the framework of the DFT with the local density approximation (LDA). The most accurate set of C ij for GaN and InN was obtained in [31] using DFT calculations with the Heyd-Scuseria-Ernzerhof hybrid functional approach, whereas the composition dependence of C ij in In x Ga 1−x N was found in [32] using the LDA-DFT method. The third-order elastic constants C ijk for the wurtzite group III-N compounds have not been determined so far.…”

Section: Pressure Dependence Of Strain and Electric Fieldmentioning

confidence: 99%

Topological phase transition and evolution of edge states in In-rich InGaN/GaN quantum wells under hydrostatic pressure

Łepkowski

Bardyszewski

2016

J. Phys.: Condens. Matter

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Combining the k · p method with the third-order elasticity theory, we perform a theoretical study of the pressure-induced topological phase transition and the pressure evolution of topologically protected edge states in InN/GaN and In-rich InGaN/GaN quantum wells. We show that for a certain range of the quantum well parameters, thanks to a negative band gap pressure coefficient, it is possible to continuously drive the system from the normal insulator state through the topological insulator into the semimetal phase. The critical pressure for the topological phase transition depends not only on the quantum well thickness but also on the width of the Hall bar, which determines the coupling between the edge states localized at the opposite edges. We also find that in narrow Hall bar structures, near the topological phase transition, a significant Rashba-type spin splitting of the lower and upper branches of the edge state dispersion curve appears. This effect originates from the lack of the mirror symmetry of the quantum well potential caused by the built-in electric field, and can be suppressed by increasing the Hall bar width. When the pressure increases, the energy dispersion of the edge states becomes more parabolic-like and the spin splitting decreases. A further increase of pressure leads to the transition to a semimetal phase, which occurs due to the closure of the indirect 2D bulk band gap. The difference between the critical pressure at which the system becomes semimetallic, and the pressure for the topological phase transition, correlates with the variation of the pressure coefficient of the band gap in the normal insulator state.

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“…The elastic constants of other mixed wurtzite-type nitrides, namely (Al,Ga)N, (Al,In)N, or (In,Ga)N, are found to depend linearly on composition. 28 Deviations from this Vegard's rule behavior are small and typically of the order of a few percent only. By contrast, (Al,Sc)N apparently does not follow this trend.…”

Section: Microscopic Origin Of C33 Softeningmentioning

confidence: 97%

First-principles calculation of electroacoustic properties of wurtzite (Al,Sc)N

Urban,

Ambacher,

Elsässer

2020

Preprint

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We study the electroacoustic properties of aluminum scandium nitride crystals Al1−xScxN with the metastable wurtzite structure by means of first-principles calculations based on density functional theory. We extract the material property data relevant for electroacoustic device design, namely the full tensors of elastic and piezoelectric constants. Atomistic models were constructed and analyzed for a variety of Sc concentrations 0 ≤ x ≤ 50%. The functional dependence of the material properties on the scandium concentration was extracted by fitting the data obtained from an averaging procedure for different disordered atomic configurations. We give an explanation of the observed elastic softening and the extraordinary increase in piezoelectric response as function of Sc content in terms of an element specific analysis of bond lengths and bond angles.

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Inapplicability of Martin transformation to elastic constants of zinc-blende and wurtzite group-III nitride alloys

Cited by 17 publications

References 31 publications

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Topological insulator with negative spin-orbit coupling and transition between Weyl and Dirac semimetals in InGaN-based quantum wells

Topological phase transition and evolution of edge states in In-rich InGaN/GaN quantum wells under hydrostatic pressure

First-principles calculation of electroacoustic properties of wurtzite (Al,Sc)N

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