Valence and Conduction Band Structure and Infrared Optical Properties of Tellurium in the Presence of Pressure

Enderlein, R.; Haché, Alain

doi:10.1002/pssb.2220600230

Cited by 9 publications

(3 citation statements)

References 16 publications

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“…Thus shear strain must contribute dominantly in our experiment. Furthermore, an induced shear strain should change the spin-split VB gap due a change in SOI 48 ; this is observed in our experiment. We propose that these dynamic shifts in the first 30 ps arise due to lifting of the spin degeneracy and the decrease of the spin-split VB gap by photoinduced shear strain generation in Te helices, as shown schematically in Fig.…”

Section: Resultssupporting

confidence: 72%

Ultrafast photoinduced band splitting and carrier dynamics in chiral tellurium nanosheets

et al. 2020

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Trigonal tellurium (Te) is a chiral semiconductor that lacks both mirror and inversion symmetries, resulting in complex band structures with Weyl crossings and unique spin textures. Detailed time-resolved polarized reflectance spectroscopy is used to investigate its band structure and carrier dynamics. The polarized transient spectra reveal optical transitions between the uppermost spin-split H 4 and H 5 and the degenerate H 6 valence bands (VB) and the lowest degenerate H 6 conduction band (CB) as well as a higher energy transition at the Lpoint. Surprisingly, the degeneracy of the H 6 CB (a proposed Weyl node) is lifted and the spin-split VB gap is reduced upon photoexcitation before relaxing to equilibrium as the carriers decay. Using ab initio density functional theory (DFT) calculations, we conclude that the dynamic band structure is caused by a photoinduced shear strain in the Te film that breaks the screw symmetry of the crystal. The band-edge anisotropy is also reflected in the hot carrier decay rate, which is a factor of two slower along the c-axis than perpendicular to it. The majority of photoexcited carriers near the band-edge are seen to recombine within 30 ps while higher lying transitions observed near 1.2 eV appear to have substantially longer lifetimes, potentially due to contributions of intervalley processes in the recombination rate. These new findings shed light on the strong correlation between photoinduced carriers and electronic structure in anisotropic crystals, which opens a potential pathway for designing novel Te-based devices that take advantage of the topological structures as well as strong spin-related properties.

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Section: Resultssupporting

confidence: 72%

Ultrafast photoinduced band splitting and carrier dynamics in chiral tellurium nanosheets

et al. 2020

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“…Since Te does not exhibit crystal-inversion symmetry, Kramer's degeneracy is not required at the non-TRIM H point. Nonetheless, because of the threefold screw symmetry of the helices, the CB state H 6 exhibits a twofold degeneracy [23], which is protected provided that the hexagonal lattice and the helical atomic ordering are preserved.…”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Novel Family of Chiral-Based Topological Insulators: Elemental Tellurium under Strain

et al. 2013

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Employing ab initio electronic structure calculations, we predict that trigonal tellurium consisting of weakly interacting helical chains undergoes a trivial insulator to strong topological insulator (metal) transition under shear (hydrostatic or uniaxial) strain. The transition is demonstrated by examining the strain evolution of the band structure, the topological Z 2 invariant and the concomitant band inversion. The underlying mechanism is the depopulation of the lone-pair orbitals associated with the valence band via proper strain engineering. Thus, Te becomes the prototype of a novel family of chiral-based three-dimensional topological insulators with important implications in spintronics, magneto-optics, and thermoelectrics. DOI: 10.1103/PhysRevLett.110.176401 PACS numbers: 71.15.Ap, 72.25.Dc, 73.20.At, 73.43.Nq The recent discovery of three-dimensional (3D) topological insulators (TIs) has sparked intense efforts in the search for novel materials that exhibit this new quantum-mechanical state of matter driven by strong spin-orbit coupling, which leads to the appearance of spin-momentum-locked topologically protected surface states with a Dirac-cone energy dispersion [1][2][3]. Ongoing research efforts focus primarily on the prototypical family of Bi 2 Te 3 , Bi 2 Se 3 , and Sb 2 Te 3 3D TIs, which exhibit a quintuple layered structure along the c axis of the hexagonal lattice. The intra-and interlayer coupling within one quintuple layer is covalentlike while the interaction between two quintuple layers is much weaker, predominantly of the van der Waals type [3][4][5].The heavier group-VI elements selenium and tellurium are ubiquitous in most of the recently discovered binary or ternary TIs and exhibit a wide variety of interesting properties under pressure. They undergo complex structural changes [6], exhibit semiconductor-to-metal transitions [7], have unusual melting curves [8], and some of their high-pressure phases are superconducting at low temperatures [6]. At ambient conditions, tellurium has a trigonal crystal structure (Te-I) with space group D 4 3 consisting of weakly interacting infinite helical chains arranged in a hexagonal array, which spiral around axes parallel to c. The unit cell shown in Fig. 1(a) has three atoms at the positions (u, 0, 0), (0, u, 1=3), and ( " u, " u, 2=3) in units of the lattice vectors [9], where u is the internal atomic position parameter. Each atom forms strong covalentlike intrachain bonds with its two nearest neighbors (NNs) and weak van der Waals-like interchain bonds with its four next NNs, with bond lengths of r ¼ 2:91 # A and R ¼ 3:43 # A, respectively. This unique feature is reflected in liquid-state studies of Te which showed that the chain structure is retained above the melting temperature [8].In this Letter we predict that Te-I, a noncentrosymmetric material, becomes a strong TI or topological metal (TM) under application of shear or uniform and uniaxial strain, respectively. In most reported TIs to date, the band inversion and the gap closing occur n...

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“…4(a). The 3500-nm probe monitors the valence band to conduction band transition, whereas the 5800-nm probe monitors intervalence band transitions, several of which, in the midinfrared region, have been found in literature [20,[58][59][60][61]. On the other hand, thin flakes show a negative transmission signal (induced absorption), thereby indicating transitions from midgap trap states to the conduction band as shown in Fig.…”

mentioning

confidence: 86%

Infrared ultrafast spectroscopy of solution-grown thin film tellurium

Iyer

Segovia

et al. 2019

Phys. Rev. B

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Several materials studied intensively in their bulk forms several decades ago have re-emerged in recent years in their thin film and monolayer manifestations. Tellurium, like black phosphorus, is one such elemental twodimensional material with promising semiconducting properties for electronic and optoelectronic applications. To study fundamental carrier properties such as hot carrier relaxation and recombination, we performed ultrafast femtosecond pump-probe spectroscopy on thin flakes of solution-grown tellurium. To access the low band gap of tellurium, we used infrared, near-band-gap and below-band-gap probes to monitor the relaxation processes. Sweeping the probing wavelengths across the band gap helps to shed light on the anisotropic band structure of the material. We find that relaxation in flakes of 60-160 nm thickness is on the order of 100 s of picoseconds. Thinner flakes (10-20 nm), on the other hand, exhibit fast relaxation times of sub-20 ps. Radiative recombination is identified as the relaxation mechanism in thick flakes, whereas midgap trap states arising from surface defects and impurities are responsible for the fast relaxation in thin flakes. A diffusion-recombination model accounting for the surface defect and radiative recombinations explains the experimental data well.

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Valence and Conduction Band Structure and Infrared Optical Properties of Tellurium in the Presence of Pressure

Cited by 9 publications

References 16 publications

Ultrafast photoinduced band splitting and carrier dynamics in chiral tellurium nanosheets

Ultrafast photoinduced band splitting and carrier dynamics in chiral tellurium nanosheets

Novel Family of Chiral-Based Topological Insulators: Elemental Tellurium under Strain

Infrared ultrafast spectroscopy of solution-grown thin film tellurium

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