Electronic band structure of epitaxial PbTe (111) thin films observed by angle-resolved photoemission spectroscopy

Ye, Zhenyu; Cui, Shengtao; Shu, Tianyu; Ma, Songsong; Liu, Yang; Sun, Zhe; Luo, Jun-Wei; Wu, Huizhen

doi:10.1103/physrevb.95.165203

Cited by 7 publications

(4 citation statements)

References 41 publications

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“…As shown in Figure c, for intrinsic PbTe the conduction and valence bands are mainly attributed to the p‐orbitals of the Pb and Te atoms respectively, confirming that the band ordering at the L points is ordinary. The topologically trivial nature of intrinsic PbTe is consistent with our previous ARPES observations on PbTe film surfaces . However, after introducing Te Pb into PbTe, the orbitals near the L points are switched, as shown in Figure d, where the conduction and valence band edges are derived from the p‐orbitals of Te and Pb, respectively.…”

Section: Resultssupporting

confidence: 89%

Realization of a New Topological Crystalline Insulator and Lifshitz Transition in PbTe

Guo

Xiao

et al. 2018

Adv Funct Materials

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Topological materials boast exotic metallic surface states with linear dispersion and spin-momentum locking, which makes them potential candidates for dissipationless electronic and spintronic devices. Here, it is theoretically predicted that intrinsic Te antisite defects (Te Pb ) in the narrow-gap semiconductor PbTe induce a band inversion, turning it into a topological crystalline insulator (TCI). To experimentally verify the exotic properties, Te Pb antisites are introduced into PbTe crystals via nonstoichiometric growth by molecular beam epitaxy. Semimetallic resistivity and distinct quantum oscillations are observed on the Te Pb doped PbTe. Most importantly, a π Berry phase is unambiguously revealed by a Landau index analysis, demonstrating the Dirac fermion nature of the topological surface states. The discovered TCI nature in Te Pb doped PbTe is further explored using magneto-transport measurements under external pressure, and the theoretical calculations of band structures with applying pressure indicate a pressure-induced Lifshitz transition. Besides, it is proposed that the contribution of bulk states to transport can be reduced by enlarging the inverted gap with strain.

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Section: Resultssupporting

confidence: 89%

Realization of a New Topological Crystalline Insulator and Lifshitz Transition in PbTe

Guo

Xiao

et al. 2018

Adv Funct Materials

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“…High quality single crystalline PbTe films studied here were grown on (111) BaF 2 substrates by molecular beam epitaxy (MBE) and described in detail in [17]. The PbTe thin film has a thickness of ∼20 nm to meet the transmission measurements.…”

Section: Samplementioning

confidence: 99%

Ultrafast dynamics of pure many-body effect and its competition with bandgap widening via electron–phonon coupling in PbTe thin films

Luo¹,

Shu²,

Chen³

et al. 2019

Semicond. Sci. Technol.

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Bandgap renormalization (BGR), or bandgap narrowing effect, is one of the many-body effects predicted by many-body theory in semiconductor physics. However, pure BGR effect has never been observed experimentally although the mixed effect of BGR with lattice-heating induced bandgap narrowing was reported in GaAs and CdTe semiconductors. PbTe has a positive temperature coefficient of bandgap. Its lattice-heating induced bandgap narrowing can be eliminated so that the pure BGR effect is possibly observed. However, that has never been reported so far because the BGR effect is weak in PbTe due to its huge dielectric screening. We study the ultrafast dynamics of photo-excited carriers in PbTe films using near-infrared femtosecond-resolved transient differential transmission (TDT) spectroscopy. A complex oscillation-like damped decay dynamics is observed. A negative dip, a fingerprint signature of BGR effect, occurs immediately after the thermalization process of the photo-excited carriers. As such, we have observed a pure BGR effect in PbTe for the first time, strongly supporting the many-body theory. Meanwhile, we have also observed a dynamic transition from a transient absorption enhancement to absorption saturation, revealing the emergence of a slow latticeheating induced bandgap widening via carrier-phonon couplings. Based on a two-temperature model, a simulation computation is carried out, supporting the lattice-heating induced bandgap widening leads to the dynamic transition. A phenomenological dynamic model is developed, including three dynamic components: the thermalization of the photo-excited carriers, recombination of the thermalized carriers and lattice-heating induced bandgap widening, and used to best fit the excitation-power dependent TDT dynamics. Time constants and strengths of the three dynamic components are obtained for different excitation powers. Time constant variation with the excitation power reveals different roles of the carrier-carrier and carrierphonon scattering in the thermalizing process, as well as of free carrier and exciton recombination in the decaying process of hot carriers.

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“…Numerous PbTe-based nanomaterials have been fabricated using various fabrication techniques. For example, films with nanometer-scale thickness were successfully prepared by electrodeposition, 33 vacuum deposition, 34 or molecular beam epitaxy, 35 while the wafer-scale pattered nanowire thin arrays were obtained through lithographically patterned electrodeposition. 36 Nonetheless, only few works have been reported for the fabrication of PbTe thin-films from individual NCs and the evaluation of their transport properties.…”

Section: Discussionmentioning

confidence: 99%

Probing of Thermal Transport in 50 nm Thick PbTe Nanocrystal Films by Time-Domain Thermoreflectance

et al. 2018

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Bottom-up fabrication of thermoelectric (TE) materials from colloidal nanocrystal (NC) building blocks can substantially increase their TE efficiency, e.g., by reducing lattice thermal conductivity. In this work, we first synthesized 10-nm spherical phase-pure oleate-capped PbTe NCs with narrow size distribution and employed them to fabricate the 110-nm thick films on insulating SiO2/Si substrates. Here, we used the spin-coating with subsequent ligand exchange procedure to ensure strong coupling interactions between the NCs. Using the dark conductivity measurements, we confirmed the semiconducting behavior and the Schottky-type electrical field-dependent conductivity mechanism in the resultant thin films. We then probed the thermal transport in the thin-film by means of a time-domain thermoreflectance (TDTR) method. For this purpose, we used a customized state-of-the-art system based on a picosecond thermoreflectance instrument, which enables area-selective analysis with the spatial resolution down to 5 m. The results show that as-fabricated PbTe NC films exhibit ultralow thermal conductivity of ca. 1.52 W m-1 K-1. All in all, the transport properties findings suggest potential of the proposed quick and cost-effective spin-coating strategy for bottom-up fabrication of nanostructured TE films from high-quality colloidal NC building blocks.

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Electronic band structure of epitaxial PbTe (111) thin films observed by angle-resolved photoemission spectroscopy

Abstract: Using angle-resolved photoemission spectroscopy (ARPES), we studied bulk and surface electronic band structures of narrow-gap semiconductor lead telluride (PbTe) thin films grown by

Cited by 7 publications

References 41 publications

Realization of a New Topological Crystalline Insulator and Lifshitz Transition in PbTe

Realization of a New Topological Crystalline Insulator and Lifshitz Transition in PbTe

Ultrafast dynamics of pure many-body effect and its competition with bandgap widening via electron–phonon coupling in PbTe thin films

Probing of Thermal Transport in 50 nm Thick PbTe Nanocrystal Films by Time-Domain Thermoreflectance

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