Structural phase transitions of (Bi1−xSbx)2(Te1−ySey)3 compounds under high pressure and the influence of the atomic radius on the compression processes of tetradymites

Zhao, Jinggeng; Yu, Zhenhai; Hu, Qingyang; Wang, Yong; Schneeloch, John; Li, Chunyu; Zhong, Ruidan; Wang, Yi; Liu, Zhiguo; Gu, Genda

doi:10.1039/c6cp07324g

Cited by 18 publications

(26 citation statements)

References 76 publications

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“…In order to further differentiate the two superconductors, we estimate the upper critical magnetic field (H c2 ) for the first and the second superconducting phases of BTS and BSTS by using the Werthamer-Helfand-Hohenberg (WHH) formula [39]: The electronic state of topological insulators is protected by time-reversal symmetry [1,3,40,41] and therefore structural stability is one of the key issues for understanding the superconductivity found in the pressure range of our experiments. It is known that BTS maintains its tetradymite structure to 8 GPa [29,42], but there are no reports of the high pressure structure of BSTS. Thus, we carried out high pressure X-ray diffraction measurements on BSTS.…”

Section: Resultsmentioning

confidence: 99%

“…To investigate whether the superconducting phases found in pressurized BTS and BSTS still possess a non-trivial topological nature, we calculated the band structures for the M and T phases for BTS based on the high pressure X-ray diffraction results [29]. Because the implied atomic disorder in the unit cell of BSTS makes the appropriate computations difficult, they were performed only for BTS.…”

Section: Resultsmentioning

confidence: 99%

“…It can produce disorder, defects and inhomogeneity in materials, however, and so is often not ideal. Pressure, on the other hand, is a clean way to realize the tuning of interactions in solids without introducing chemical complexity, and thus has been successfully adopted in the study of some TIs [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Our study of the evolution of the topological surface states on optimized tetradymite BTS and BSTS crystals (by optimized we mean highest bulk resistivities at ambient pressure) at high pressures has been reported recently, for example [34].…”

Section: Introductionmentioning

confidence: 99%

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Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Cai

Kushwaha

Guo

et al. 2018

Phys. Rev. Materials

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We show that two different superconducting phases exist at high pressures in the optimized tetradymite topological insulators Bi 2 Te 2 Se (BTS) and Bi 1.1 Sb 0.9 Te 2 S (BSTS). The superconducting phases emerge at structural phase transitions -the first at ~8.4 GPa for BTS and ~12.4 GPa for BSTS, and the second at 13.6 GPa for BTS and 20.4 GPa, for BSTS. Electronic structure calculations show that these phases do not have topological character. Comparison of our results with prior work on Bi 2 Se 3 , Bi 2 Te 3 and (Bi,Sb) 2 (Se,Te) 3 allows us to uncover a universal phase diagram for pressure-induced superconductivity in tetradymites, providing a basis for understanding the relationships between topological behavior, crystal structure, and superconductivity for these materials.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Cai

Kushwaha

Guo

et al. 2018

Phys. Rev. Materials

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“…1), and near 6-7 GPa or somewhat above they all undergo a phase transition to the monoclinic C2/m lattice. 30,53,[75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91] As shown by studies on high-quality single crystals of Bi 2 Te 3 , the pressure behavior of its Seebeck coefficient depends strongly on carrier concentration. 51,53 For example, in undoped p-type crystals with carrier concentrations of about 10 17 cm −3 and below, an applied pressure of 2-4 GPa induces a double p-n-p sign inversion [ p-Bi 2 Te 3 (1) in Fig.…”

Section: A (Bisb) 2 (Tese) 3 Thermoelectricsmentioning

confidence: 99%

Strategies and challenges of high-pressure methods applied to thermoelectric materials

Morozova

Korobeinikov

Ovsyannikov

2019

Journal of Applied Physics

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We describe the current state of experimental studies of the effects of applied high pressure or stress on the thermoelectric properties and performance parameters of thermoelectric materials, as well as the challenges faced in this area and possible directions for future work. We summarize and analyze literature data on the effects of high pressure on the Seebeck coefficient (thermoelectric power) of different materials that are related to common families of thermoelectrics, such as Bi

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“…We use transport measurements under applied pressure to show this, because pressure is a clean way to tune electronic states in materials without introducing chemical complexity. High pressure measurements addressing other issues have been employed in studies on some TIs [21][22][23][24][25][26] , but here we report the first high pressure investigations of insulating BTS and BSTS single crystals that directly address the interdependence of the surface and bulk state conductances. The surprising result is that above temperatures of ~10 K, the bulk and surface states appear to be intermixing and the bulk conductance changes by orders of magnitude, while, below 10 K, the surface state conductance changes very little with temperature or pressure, an indication that they are truly independent at that temperature and below.…”

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confidence: 99%

Independence of topological surface state and bulk conductance in three-dimensional topological insulators

et al. 2018

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commonly exhibit high bulk conductivities, hindering the characterization of the surface state charge transport. The optimally doped topological insulators Bi 2 Te 2 Se and Bi 2-x Sb x Te 2 S, however, allow for such characterizations to be made. Here we report the first experimental comparison of the topological surface states and bulk conductances of Bi 2 Te 2 Se and Bi 1.1 Sb 0.9 Te 2 S, based on temperature-dependent high-pressure measurements. We find that the surface state conductance at low temperatures remains constant in the face of orders of magnitude increase in the bulk state conductance, revealing in a straightforward way that the topological surface states and bulk states are decoupled at low temperatures, consistent with theoretical models, and confirming topological insulators to be an excellent venue for studying charge transport in 2D Dirac electron systems.Topological insulators (TIs) are, theoretically, quantum materials that display a bulk band gap like an ordinary insulator, but a conducting surface state that is topologically protected due to a combination of spin-orbit interactions and time-reversal symmetry 1-6 . The topologically non-trivial nature of the spin-helical Dirac fermion surface states in TIs has attracted wide interest in the research community because it results in rich new physics and materials that have potential applications in quantum technology 7,8 .An ideal TI should have topologically-protected metallic surface states (TSS), but also an electrically insulating bulk. Unfortunately, early generations of bulk TIs, materials such as the M 2 X 3 (M=Bi and Sb, X=S, Se and Te) tetradymites, are not typically insulating 2,[9][10][11][12][13] , which prevented the early characterization of many of the charge transport properties of the surface states. Recently, however, insulating bulk crystals of the tetradymite TI variants Bi 2 Te 2 Se (BTS) 14-16 and Bi 1.1 Sb 0.9 Te 2 S (BSTS) 17,18 have been grown; these two materials are high quality topological insulators with very low bulk carrier concentrations 16,[18][19][20] . The bulk bandgaps of BTS and the BSTS are ~310 meV 14,19,20 and ~350 meV 18 , and, in the latter material, the Dirac crossing in the TSS band is well isolated from the bulk states. These compounds provide an ideal platform for studying the evolution of the TSS conductance and its connections with the conductance of the bulk state.Although it is widely accepted that topological surface states and bulk electronic states should act independently, the degree to which they might or might not intermix has not been addressed in a straightforward experiment. We address that shortcoming

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Structural phase transitions of (Bi_1−xSb_x)₂(Te_1−ySe_y)₃ compounds under high pressure and the influence of the atomic radius on the compression processes of tetradymites

Abstract: Different structural evolutions between (Bi1−xSbx)2(Te1−ySey)3 and tellurides indicates that the compression processes of tetradymites are related to atomic radius.

Cited by 18 publications

References 76 publications

Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Strategies and challenges of high-pressure methods applied to thermoelectric materials

Independence of topological surface state and bulk conductance in three-dimensional topological insulators

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