Preparation and Characterization of Sn-BSTS Topological Insulator for Universality Test of the Quantum Hall Effect

Misawa, Tetsuro; Fukuyama, Yasuhiro; Okazaki, Yoshiaki; Nakamura, Shuji; Nasaka, Nariaki; Sasagawa, T.; Kaneko, Nobu‐Hisa

doi:10.1109/tim.2017.2650658

Cited by 8 publications

(8 citation statements)

References 24 publications

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“…Figure 3a presents the X-ray diffraction patterns collected at pressures up to 36.1 GPa for BSTS. Like other tetradymite TIs, BSTS crystallizes in a rhombohedral (R) unit cell at ambient pressure [36,43] and maintains the R phase up to ~10.9 GPa. It then undergoes a structural phase transition at pressures between 10.9 and 13.1 GPa.…”

Section: Resultsmentioning

confidence: 99%

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%

Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Cai

Kushwaha

Guo

et al. 2018

Phys. Rev. Materials

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“…To illustrate the effect of pressure on the conductances of the TSS in BTS and BSTS more quantitatively, we describe the resistance-temperature (R-T) behavior of these materials via the commonly-employed two channel model 17,28 . Because conductivities are additive, the total conductance (G tot ) is then the sum of a thermally activated bulk conductance (G bul ) and a metallic surface conductance (G sur ) 28 :…”

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confidence: 99%

“…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][15][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.…”

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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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“…[1][2][3][4][5] The first predicted and confirmed by angle-resolved photoemission spectroscopy and scanning tunneling microscopy. [12][13][14][15] In high-quality TIs with a large bulk bandgap and low bulk carrier concentration, the conducting surface state and bulk charge transport can be well separated and identified at low temperature, such as in Bi 2 Te 2 Se [16,17] and Bi 1.1 Sb 0.9 Te 2 S. [18,19] Increasingly recent investigations have focused on the possible topological superconductivity in 3D TIs and TSMs. Although it remains problematic to clarify the nature of the Cooper pairs existing in the new quantum state in the parent compound, the chemical doping-induced superconductivity in Cu-doped Bi 2 Se 3 has inspired enormous experimental and theoretical efforts to study potential topological superconductivity.…”

Section: Introductionmentioning

confidence: 99%

Pressure‐Induced Superconductivity in HgTe Single‐Crystal Film

Zhang

Zheng

et al. 2022

Advanced Science

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HgTe film is widely used for quantum Hall well studies and devices, as it has unique properties, like band gap inversion, carrier‐type switch, and topological evolution depending on the film thickness modulation near the so‐called critical thickness (63.5 Å), while its counterpart bulk materials do not hold these nontrivial properties at ambient pressure. Here, much richer transport properties emerging in bulk HgTe crystal through pressure‐tuning are reported. Not only the above‐mentioned abnormal properties can be realized in a 400 nm thick bulk HgTe single crystal, but superconductivity is also discovered in a series of high‐pressure phases. Combining crystal structure, electrical transport, and Hall coefficient measurements, a p‐n carrier type switching is observed in the first high‐pressure cinnabar phase. Superconductivity emerges after the semiconductor‐to‐metal transition at 3.9 GPa and persists up to 54 GPa, crossing four high‐pressure phases with an increased upper critical field. Density functional theory calculations confirm that a surface‐dominated topologic band structure contributes these exotic properties under high pressure. This discovery presents broad and efficient tuning effects by pressure on the lattice structure and electronic modulations compared to the thickness‐dependent critical properties in 2D and 3D topologic insulators and semimetals.

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Preparation and Characterization of Sn-BSTS Topological Insulator for Universality Test of the Quantum Hall Effect

Cited by 8 publications

References 24 publications

Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Universal superconductivity phase diagram for pressurized tetradymite topological insulators

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

Pressure‐Induced Superconductivity in HgTe Single‐Crystal Film

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