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Crystal structures of bismuth tellurohalides. All bismuth-based compounds under consideration were calculated in the hexagonal P3m1 (left image) and orthorhombic Pnma (right image) structures. BiTeCl and BiTeI were also considered in the hexagonal P63mc phase (central image) which is the structure of BiTeCl at ambient pressure.
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We study the possibility of pressure-induced transitions from a normal semiconductor to a topological insulator (TI) in bismuth tellurohalides using density functional theory and tight-binding method. In BiTeI this transition is realized through the formation of an intermediate phase, a Weyl semimetal, that leads to modification of surface state di...
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... It is initially a large band gap semiconductor with a pronounced Rashba-type spin-orbit interaction, and it has been forecasted to transform into a robust topological insulator when subjected to moderate pressure [4] via an intermediate Weyl semimetalic phase [11,12]. The utilization of density functional theory (DFT) with the application of U enhances the prediction of electronic characteristics [13] for highly correlated systems. ...
In recent years, Bismuth tellurohalide has gained significant attention as a possible candidate for spintronics applications. Among them, BiTeI is one such layered material that shows Rashba spin splitting responsible for transport phenomenon. On the basis of density functional theory calculations using full-potential local-orbital code, we studied the electronic and magnetic properties of Bi2TeMnI2 compound. Our study shows an energy band gap of 1.18 eV for the parent material BiTeI. The main contribution around the Fermi level are from the Bi-6p, I-5p and Te-5p states. Upon doping Mn atom independently to Bi, Te and I site, we found that Te site is energetically most favorable. With Mn doped to Te site, the material is found to transform to ferromagnetic semiconducting state with magnetic easy-axis along [001] with magnetic moment of 3 μB per unit cell. The magnetic moment is found to alter interestingly with the implementation of Hubbard-potential (U). The value first reduces to 1 μB for U = 3 eV and starts changing with increasing value of U. Due to internal ferromagnetic ordering and strong correlation effect, this compound seems to be a promising candidate for spintronics and quantum computing.
... An exceptional range of thermodynamic conditions is made available through LRS-DAC methods, allowing investigators to effectively break chemical bonds and induce reactions that otherwise could not occur [41][42][43]. It is well-known that the electronic structure and chemical bonding of atoms, molecules, and crystals can be modified greatly through the application of pressure [1,44,45], potentially reducing activation barriers to reaction [1]. ...
The synthesis of advanced materials at high pressures has been an area of growing research interest for several decades. This article is the third in a three-part series that reviews Laser Materials Processing Within Diamond Anvil Cells (L-DACs). Part III focuses on the practice of Laser Reactive Synthesis Within Diamond Anvil Cells (LRS-DAC). During LRS-DAC processing, chemicals are precompressed within diamond anvil cells, then microscale chemical reactions are induced by focused laser beams. The method is distinguished from the well-known Laser-Heated Diamond Anvil Cell (LH-DAC) technique (see Part I) through the existence of chemical precursors (reactants), end-products, and quantifiable changes in chemical composition upon reaction. LRS-DAC processing provides at least three new degrees of freedom in the search for advanced materials (beyond adjusting static pressures and temperatures), namely: laser-excitation/cleavage of chemical bonds, time-dependent reaction kinetics via pulsed lasers, and pressure-dependent chemical kinetics. All of these broaden the synthetic phase space considerably. Through LRS-DAC experimentation, it is possible to obtain increased understanding of high-pressure chemical kinetics—and even the nature of chemical bonding itself. Here, LRS-DAC experimental methods are reviewed, along with the underlying chemistry/physics of high-pressure microchemical reactions. A chronology of key events influencing the development of LRS-DAC systems is provided, together with a summary of novel materials synthesised, and unusual chemical reactions observed. Current gaps in knowledge and emerging opportunities for further research are also suggested.
... Compounds in the BiTeX family have been shown to exhibit drastic changes in their physical properties when external pressure is applied. BiTeI and BiTeBr are believed to undergo pressure-driven topological quantum phase transitions [8][9][10][11][12][13], while all of the compounds have shown evidence of pressure-induced structural transitions [13][14][15] and pressure-induced superconductivity [16][17][18][19][20]. Compounds with the formula Bi 2 TeI [21,22] and Bi 3 TeI [23] have also been synthesized. These compounds incorporate Bi-bilayers in the van der Waals gap between layers of BiTeI [21][22][23][24][25][26][27]. ...
We report a series of high-pressure electrical transport, magnetic susceptibility, and x-ray diffraction measurements on single crystals of the weak topological insulator Bi2TeI and the topological metal Bi3TeI. Room temperature x-ray diffraction measurements show that both materials go through a series of pressure-induced structural transitions and eventually adopt a disordered bcc alloy structure at high pressure. A re-analysis of the published data on BiTeI indicates that this material also adopts a disordered bcc structure at high pressure, in contrast to the previously suggested P4/nmm structure. We find that Bi2TeI and Bi3TeI become superconducting at 13 GPa and 11.5 GPa, respectively. The superconducting critical temperature Tc of the bcc phase reaches maximum values of 7 K and 7.5 K for Bi2TeI and Bi3TeI, respectively and dTc/dP < 0 in both cases. The results indicate that disordered alloy bcc superconducting phases appear to be a universal feature of both the Bi-Te and Bi-Te-I systems at high pressure.
... How can pressure help in inducing a TQPT? Pressure is a thermodynamic parameter that allows a finely tuning of the volume, lattice parameters, bond lengths, effective hybridization, electron density, and crystal field splitting of materials [18,19,[24][25][26]. These parameters affect the electronic band structure of the material that could lead to a decrease in the band gap and help the SOC to produce a BI [18-20, 25, 27]. ...
Research on topological and topological crystalline insulators is one of the most intense and exciting topics due to its fascinating fundamental science and potential technological applications. Pressure (strain) is one potential pathway to induce the non-trivial topological phases in some topologically trivial (normal) insulating or semiconducting materials. In the last ten years, there have been substantial theoretical and experimental efforts from condensed-matter scientists to characterize and understand pressure-induced topological quantum phase transitions. In particular, a promising enhancement of the thermoelectric performance through pressure-induced topological quantum phase transition has been recently realized; thus evidencing the importance of this subject in society. Since the pressure effect can be mimicked by chemical doping or substitution in many cases, these results have opened a new route to develop more efficient materials for harvesting green energy at ambient conditions. Therefore, a detailed understanding of the mechanism of pressure-induced topological quantum phase transitions in various classes of materials with spin-orbit interaction is crucial to improve their properties for technological implementations. Hence, this review focuses on the emerging area of pressure-induced topological quantum phase transitions to provide a comprehensive understanding of this subject from both theoretical and experimental points of view. In particular, it covers the Raman signatures of detecting the topological transitions (under pressure), some of the important pressure-induced topological and topological crystalline insulators of the various classes of spin-orbit coupling materials, and provide future research directions in this interesting field.
... Meanwhile, a theoretical study predicted two high-pressure structural phase transitions (P3m1 → Pnma → P4/nmm) in BiTeI [5]. In other recent studies, Rusinov et al. studied both the topological and crystal phase transitions in the bismuth tellurohalides (BiTeX, X = I, Br, Cl) through density-functional calculations [6]. Qi et al. reported the discovery of superconductivity in both BiTeI and BiTeBr induced by pressure, while the resistivity at higher temperatures still exhibits semiconducting behavior [7]. ...
Based on crystal structural search and ab initio calculations, we report pressure-induced structural and electronic phase transitions for the semiconductor indium tellurium iodine (InTeI). We have found two structures belonging to the same space group of InTeI at high pressure (labeled as P4/nmm−I and P4/nmm−II, respectively), where P4/nmm−II is metastable. Our calculation results show that the ambient P21/c phase transforms to a tetragonal P4/nmm−I phase at about 15 GPa, characterized by the appearance of metallization and superconductivity with Tc of around 7 K. Besides, band-structure calculations suggest that the InTeI system undergoes a pressure-induced electronic phase transition from a direct to indirect band gap in the P21/c phase. On the application of atomic substitution, the superconducting temperature Tc of InTeI can be further raised to around 9.7 K if the iodine atoms are replaced by the lighter chlorine atoms in the P4/nmm−I phase. The results pave the way for applying of Indium tellurohalide in optoelectronic devices and demonstrate a method that adjusts electronic properties by pressure or atomic substitution.
... In addition, theoretical calculations and experiments have confirmed that BiTeXs show interesting transitions, such as topological quantum phase transition and superconducting state transition under certain pressure [118,[130][131][132][133][134][135][136][137][138][139][140]. To investigate the topological phase transition of BiTeXs, Bahramy modified the chemical bonds of BiTeI by applying external hydrostatic pressure, as shown in figure 12. ...
Bismuth-based binary compounds, including Bi2Se3 and Bi2Te3, have attracted increasing attention as well-known topological insulators. On the other hand, bismuth-based ternary compounds exhibit diverse properties, such as, ultrahigh carrier mobility, and strong Rashba spin splitting. Moreover, they boast of superior photocatalytic properties, implying great potential to be used in a wide range of applications. The unique structure and properties of two-dimensional (2D) materials, especially the extraordinary electronic and optical properties of 2D Bi2O2Se, have given rise to significant research interests for the exploration of 2D bismuth-based ternary compounds. In this review, we will comprehensively discuss the properties of three important families of bismuth-based ternary compounds, including Bi2O2X (X = S, Se, Te), BiTeX (X = Cl, Br, I), and BiOX (X = Cl, Br, I). In particular, we have placed emphasis on the latest progress in their 2D forms, including their novel properties and applications. This review would aid in understanding the superior performance of bismuth-based ternary compounds and offer a perspective for future research on these emerging 2D materials.
... Although bulk states are projected to the surface when the Fermi level is at the energy of type-II WPs, there still exist Fermi arcs connecting projected WPs. Type-I and type-II WPs of opposite chiralities can annihilate when they are brought to each other, and the transition between type-I and type-II WPs can be manipulated under many experimental setups, such as elemental doping, 122 external pressure,123 and tuning magnetic orientations.124 ...
Topological semimetals (TSMs) refer to electronic gapless phases that exhibit topological band crossings around the Fermi level and have intrigued enormous research interest in the past few decades. There have been many theoretical and experimental progresses regarding TSMs, and first-principles calculations have been proven to be an instrumental tool in finding candidate materials for TSMs. In this tutorial, we will focus on two representative types of TSMs—Weyl and Dirac semimetals and summarize the recent progress from the perspective of first-principles calculations. First of all, the basic concepts of TSMs, the generic topological invariants, and the frequently used techniques within first-principles calculations are briefly introduced. Second, taking typical materials as representative examples, we summarize the characteristic electronic properties, formation mechanisms, and general methodologies for Weyl and Dirac semimetals, respectively. In the last part, we present a short review of recent progresses on other types of TSMs.
... This unique spin texture makes them highly desirable for various spintronic applications. Further interesting properties of these highly polar semiconductor materials include the bulk rectification effects [33], pressure-induced topological phase [34][35][36][37][38], superconductivity [39,40], and out-of-plane spin textures caused by coupling to orbital degree of freedom [41]. ...
Ferromagnetic materials are the widely used source of spin-polarized electrons in spintronic devices, which are controlled by external magnetic fields or spin-transfer torque methods. However, with increasing demand for smaller and faster spintronic components, utilization of spin-orbit phenomena provides promising alternatives. New materials with unique spin textures are highly desirable since all-electric creation and control of spin polarization is expected, where the strength, as well as an arbitrary orientation of the polarization, can be defined without the use of a magnetic field. In this work, we use a novel spin-orbit crystal BiTeBr for this purpose. Owning to its giant Rashba spin splitting, bulk spin polarization is created at room temperature by an electric current. Integrating BiTeBr crystal into graphene-based spin valve devices, we demonstrate for the first time that it acts as a current-controlled spin injector, opening new avenues for future spintronic applications in integrated circuits.
... While at first it was thought that the TPT of BiTeI occurred at a single critical pressure P C , it was later demonstrated that the lack of inversion symmetry imposed the existence of an intermediate Weyl semimetal (WSM) phase [41] between the trivial band insulator and topological insulator phases, yielding two critical pressures. Tight-binding [41] and first-principles calculations [42,43] predicted that this WSM phase could exist only within a narrow pressure range of 0.1-0.2 GPa, making its experimental detection technically challenging. ...
... The precise value of the critical pressure of BiTeI is still elusive to this day. Experiments have located it between 2.0 and 3.5 GPa [7,[34][35][36]38], while first-principles calculations have predicted it in a slightly wider range of pressures, from 1.6 to 4.5 GPa [31,[42][43][44]. From a theoretical point of view, predicting the critical pressure comes down to finding the gap closing pressure, which is inherently dependent on the accuracy of the calculated band gap at ambient pressure, which can be biased by the well-established underestimation of the band gap by density functional theory (DFT) [45]. ...
... Throughout this paper, we rely on the generalized gradient approximation of the Perdew-Burke-Ernzerhof (PBE-GGA) functional [74], although it has been shown to overestimate the lattice parameters at ambient pressure for this particular material [42,53,75]. Since the purpose of this paper is to investigate the temperature dependence of the TPT, we chose the functional that gives us the best overall agreement with experiment for the bare band gap and the projected orbital character of the band extrema at ambient pressure, as well as for the predicted critical pressure P C1 . ...
A topological phase transition from a trivial insulator to a Z2 topological insulator requires the bulk band gap to vanish. In the case of noncentrosymmetric materials, these phases are separated by a gapless Weyl semimetal phase. However, at finite temperature, the gap is affected by atomic motion, through electron-phonon interaction, and by thermal expansion of the lattice. As a consequence, the phase space of topologically nontrivial phases is affected by temperature. In this paper, the pressure and temperature dependence of the indirect band gap of BiTeI is investigated from first principles. We evaluate the contribution from both electron-phonon interaction and thermal expansion, and show that their combined effect drives the topological phase transition towards higher pressures with increasing temperature. Notably, we find that the sensitivity of both band extrema to pressure and topology for electron-phonon interaction differs significantly according to their leading orbital character. Our results indicate that the Weyl semimetal phase width is increased by temperature, having almost doubled by 100 K when compared to the static lattice results. Our findings thus provide a guideline for experimental detection of the nontrivial phases of BiTeI and illustrate how the phase space of the Weyl semimetal phase in noncentrosymmetric materials can be significantly affected by temperature.
... While at first it was thought that the TPT of BiTeI occurred at a single critical pressure P C , it was later demonstrated that the lack of inversion symmetry imposed the existence of an intermediate Weyl semimetal (WSM) phase [41] between the trivial band insulator and topological insulator phases, yielding two critical pressures. Tight-binding [41] and first-principles calculations [42,43] predicted that this WSM phase could exist only within a narrow pressure range of 0.1-0.2 GPa, making its experimental detection technically challenging. ...
... The precise value of the critical pressure of BiTeI is still elusive to this day. Experiments have located it between 2.0 and 3.5 GPa [7,[34][35][36]38], while first-principles calculations have predicted it in a slightly wider range of pressures, from 1.6 to 4.5 GPa [31,[42][43][44]. From a theoretical point of view, predicting the critical pressure comes down to finding the gap closing pressure, which is inherently dependent on the accuracy of the calculated band gap at ambient pressure, which can be biased by the well-established underestimation of the band gap by density functional theory (DFT) [45]. ...
... Throughout this paper, we rely on the generalized gradient approximation of the Perdew-Burke-Ernzerhof (PBE-GGA) functional [74], although it has been shown to overestimate the lattice parameters at ambient pressure for this particular material [42,53,75]. Since the purpose of this paper is to investigate the temperature dependence of the TPT, we chose the functional that gives us the best overall agreement with experiment for the bare band gap and the projected orbital character of the band extrema at ambient pressure, as well as for the predicted critical pressure P C1 . ...
A topological phase transition from a trivial insulator to a $\mathbb{Z}_2$ topological insulator requires the bulk band gap to vanish. In the case of noncentrosymmetric materials, these phases are separated by a gapless Weyl semimetal phase. However, at finite temperature, the gap is affected by atomic motion, through electron-phonon interaction, and by thermal expansion of the lattice. As a consequence, the phase space of topologically nontrivial phases is affected by temperature. In this paper, the pressure and temperature dependence of the indirect band gap of BiTeI is investigated from first principles. We evaluate the contribution from both electron-phonon interaction and thermal expansion, and show that their combined effect drives the topological phase transition towards higher pressures with increasing temperature. Notably, we find that the sensitivity of both band extrema to pressure and topology for electron-phonon interaction differs significantly according to their leading orbital character. Our results indicate that the Weyl semimetal phase width is increased by temperature, having almost doubled by 100 K when compared to the static lattice results. Our findings thus provide a guideline for experimental detection of the nontrivial phases of BiTeI and illustrate how the phase space of the Weyl semimetal phase in noncentrosymmetric materials can be significantly affected by temperature.
