S2 MethodsReagents. Bismuth nitrate (Bi(NO3)35H2O, Alfa Aesar, 99.9%), selenourea (SeC(NH2)2, Alfa Aesar, 99.9%), potassium hydroxide (KOH, S D Fine-Chem Limited (SDFCL)), sodium hydroxide (NaOH, SDFCL), Disodium EDTA (C10H14O8Na2N2H2O, SDFCL) and ethanol were used without any further purification.Synthesis procedure. 100 mg (0.206 mmol) of Bi(NO3)35H2O, 12.7 mg (0.103 mmol) of SeC(NH2)2 and 306.8 mg (0.824 mmol) of disodium EDTA were sequentially added at a 5 minutes interval into 20 ml water in a glass beaker. The solution was stirred continuously. The addition of Bi(NO3)35H2O into water results in a milky white color solution which turns into an orange color solution after the addition of SeC(NH2)2. The solution becomes clear after the addition of disodium EDTA. Finally, 120 mg (2.14 mmol) of KOH and 320 mg (8 mmol) of NaOH were added into the solution which turns the solution color black. After 10 minutes of stirring, the solution was put to rest which results in precipitation of the dark brown color nanosheets. We observed that nanosheets of similar morphology and thickness can also be obtained without using disodium EDTA, however, in that case, the required amount of water solvent is much higher, 200 ml. These were then washed with alcohol and water and centrifuged to remove disodium EDTA. The purified product was then dried in a vacuum oven at 150 C.Step I: In water, Bi(NO3)3 undergoes hydrolysis to produce BiONO3 and the process of hydrolysis is expedites in alkaline medium:Step II: Selenourea SeC(NH2)2 undergoes decomposition in alkaline medium to generate selenide ions (Se 2-) along with cyanamide (H2NCN): SeC(NH2)2 + OH -→ Se 2-+ H2NCN + H2O
Orthorhombic GeSe is ap romising thermoelectric material. However,l arge band gap and strong covalent bonding result in al ow thermoelectric figure of merit, zT % 0.2. Here,w ed emonstrate am aximum zT % 1.35 at 627 K in p-type polycrystalline rhombohedral (GeSe) 0.9 (AgBiTe 2 ) 0.1 , which is the highest value reported among GeSe based materials.T he rhombohedral phase is stable in ambient conditions for x = 0.8-0.29 in (GeSe) 1Àx (AgBiTe 2 ) x .T he structural transformation accompanies change from covalent bonding in orthorhombic GeSe to metavalent bonding in rhombohedral (GeSe) 1Àx (AgBiTe 2 ) x .(GeSe) 0.9 (AgBiTe 2 ) 0.1 has closely lying primary and secondary valence bands (within 0.25-0.30 eV), which results in high power factor 12.8 mWcm À1 K À2 at 627 K. It also exhibits intrinsically low lattice thermal conductivity (0.38 Wm À1 K À1 at 578 K). Theoretical phonon dispersion calculations reveal vicinity of aferroelectric instability,with large anomalous Born effective charges and high optical dielectric constant, which, in concurrence with high effective coordination number,l ow band gap and moderate electrical conductivity,corroborate metavalent bonding in (GeSe) 0.9 (AgBiTe 2 ) 0.1 .W econfirmed the presence of low energy phonon modes and local ferroelectric domains using heat capacity measurement (3-30 K) and switching spectroscopyinpiezoresponse force microscopy, respectively.
Orthorhombic GeSe is ap romising thermoelectric material. However,l arge band gap and strong covalent bonding result in al ow thermoelectric figure of merit, zT % 0.2. Here,w ed emonstrate am aximum zT % 1.35 at 627 K in p-type polycrystalline rhombohedral (GeSe) 0.9 (AgBiTe 2 ) 0.1 , which is the highest value reported among GeSe based materials.T he rhombohedral phase is stable in ambient conditions for x = 0.8-0.29 in (GeSe) 1Àx (AgBiTe 2 ) x .T he structural transformation accompanies change from covalent bonding in orthorhombic GeSe to metavalent bonding in rhombohedral (GeSe) 1Àx (AgBiTe 2 ) x .(GeSe) 0.9 (AgBiTe 2 ) 0.1 has closely lying primary and secondary valence bands (within 0.25-0.30 eV), which results in high power factor 12.8 mWcm À1 K À2 at 627 K. It also exhibits intrinsically low lattice thermal conductivity (0.38 Wm À1 K À1 at 578 K). Theoretical phonon dispersion calculations reveal vicinity of aferroelectric instability,with large anomalous Born effective charges and high optical dielectric constant, which, in concurrence with high effective coordination number,l ow band gap and moderate electrical conductivity,corroborate metavalent bonding in (GeSe) 0.9 (AgBiTe 2 ) 0.1 .W econfirmed the presence of low energy phonon modes and local ferroelectric domains using heat capacity measurement (3-30 K) and switching spectroscopyinpiezoresponse force microscopy, respectively.
In Weyl semimetals, there is an intriguing possibility of realizing a pseudo-magnetic field in presence of small strain due to certain special cases of static deformations. This pseudo-magnetic field can be large enough to form quantized Landau levels and thus become observable in Weyl semimetals. In this paper we experimentally show the emergence of a pseudo-magnetic field (∼ 3 Tesla) by Scanning Tunneling Spectroscopy (STS) on the doped Weyl semimetal Re-MoTe2, where distnict Landau level oscillations in the tunneling conductance are clearly resolved. The crystal lattice is intrinsically strained where large area STM imaging of the surface reveals differently strained domains where atomic scale deformations exist forming topographic ripples with varying periodicity in the real space. The effect of pseudo-magnetic field is clearly resolved in areas under maximum strain.
Majority of the A2B3 type chalcogenide systems with strong spin-orbit coupling, like Bi2Se3, Bi2Te3 and Sb2Te3 etc., are topological insulators. One important exception is Sb2Se3, where a topological non-trivial phase was argued to be possible under ambient conditions, but such a phase could be detected to exist only under pressure. In this Letter, we show that like Bi2Se3, Sb2Se3, displays generation of highly spin-polarized current under mesoscopic superconducting point contacts as measured by point contact Andreev reflection spectroscopy. In addition, we observe a large negative and anisotropic magnetoresistance in Sb2Se3, when the field is rotated in the basal plane. However, unlike in Bi2Se3, in case of Sb2Se3 a prominent quasiparticle interference (QPI) pattern around the defects could be obtained in STM conductance imaging. Thus, our experiments indicate that Sb2Se3 is a regular band insulator under ambient conditions, but due to it's high spin-orbit coupling, non-trivial spin-texture exists on the surface and the system could be on the verge of a topological insulator phase.
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