The Crystal Structure of HfTe5.

Furuseth, Sigrid; Brattås, Leif; Kjekshus, Arne; Enzell, Curt R.; Swahn, Carl‐Gunnar

doi:10.3891/acta.chem.scand.27-2367

Cited by 125 publications

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“…The low-dimensional pentatellurides, ZrTe 5 and Hf Te 5 , synthesized in 19731, exhibit a peak in the resistivity ( ρ ) as a function of temperature2. This anomaly in the resistivity has been observed at T P ~ 145 K for ZrTe 5 and T P ~ 80 K for Hf Te 5 , however, the exact temperature varies from sample to sample depending on the impurity level3.…”

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confidence: 99%

“…Subsequently, the concept of polaronic conduction10, semimetal-semiconductor phase transition11 and so on, have emerged until a recent theoretical work suggests that the monolayer of ZrTe 5 and Hf Te 5 is the most promising candidate for the quantum spin Hall due to the large bulk gap12. Suddenly, a material known for its large thermoelectric power6, resistivity anomaly1 and large positive magnetoresistance13, has been brought to our attention to study the topological properties of relativistic Dirac fermion in condensed matter physics451415161718192021.…”

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confidence: 99%

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Coexistence of topological Dirac fermions on the surface and three-dimensional Dirac cone state in the bulk of ZrTe5 single crystal

Mandal

2017

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Although, the long-standing debate on the resistivity anomaly in ZrTe5 somewhat comes to an end, the exact topological nature of the electronic band structure remains elusive till today. Theoretical calculations predicted that bulk ZrTe5 to be either a weak or a strong three-dimensional (3D) topological insulator. However, the angle resolved photoemission spectroscopy and transport measurements clearly demonstrate 3D Dirac cone state with a small mass gap between the valence band and conduction band in the bulk. From the magnetization and magneto-transport measurements on ZrTe5 single crystal, we have detected both the signature of helical spin texture from topological surface state and chiral anomaly associated with the 3D Dirac cone state in the bulk. This implies that ZrTe5 hosts a novel electronic phase of material, having massless Dirac fermionic excitation in its bulk gap state, unlike earlier reported 3D topological insulators. Apart from the band topology, it is also apparent from the resistivity and Hall measurements that the anomalous peak in the resistivity can be shifted to a much lower temperature (T < 2 K) by controlling impurity and defects.

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confidence: 99%

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Coexistence of topological Dirac fermions on the surface and three-dimensional Dirac cone state in the bulk of ZrTe5 single crystal

Mandal

2017

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“…The complexity of the ZrTe 5 electronic properties became clear since its first synthesis in 1973 [3]. The thermopower changes sign from positive to negative when cooling down across T * [4], meanwhile the resistivity increases by a factor ∼ 3 [5], and the charge carrier switches from holes, at T > T * , to electrons, for T < T * [6].…”

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Ultrafast Optical Control of the Electronic Properties ofZrTe5

et al. 2015

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We report on the temperature dependence of the ZrTe5 electronic properties, studied at equilibrium and out of equilibrium, by means of time and angle resolved photoelectron spectroscopy (tr-ARPES). Our results unveil the dependence of the electronic band structure across the Fermi energy on the sample temperature. This finding is regarded as the dominant mechanism responsible for the anomalous resistivity observed at T * ∼ 160 K along with the change of the charge carrier character from hole-like to electron-like. Having addressed these longlasting questions, we prove the possibility to control, at the ultrashort time scale, both the binding energy and the quasiparticle lifetime of the valence band. These experimental evidences pave the way for optically controlling the thermo-electric and magneto-electric transport properties of ZrTe5.

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“…The pentatellurides ZrTe 5 and HfTe 5 are layered materials [1,2] with a high concentration of the heavy p-element Te. They were found to show a remarkable electronic transition as a function of temperature (T) [3].…”

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Bipolar Conduction as the Possible Origin of the Electronic Transition in Pentatellurides: Metallic vs Semiconducting Behavior

et al. 2018

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The pentatellurides ZrTe 5 and HfTe 5 are layered compounds with one-dimensional transition-metal chains that show a not-yet-understood temperature-dependent transition in transport properties as well as recently discovered properties suggesting topological semimetallic behavior. Here, we report magnetotransport properties for two kinds of ZrTe 5 single crystals grown with the chemical vapor transport (CVT) and the flux method (Flux), respectively. They show distinct transport properties at zero field: The CVT crystal displays a metallic behavior with a pronounced resistance peak and a sudden sign reversal in thermopower at approximately 130 K, consistent with previous observations of the electronic transition; in striking contrast, the Flux crystal exhibits a semiconducting-like behavior at low temperatures and a positive thermopower over the whole temperature range. For both samples, strong effects on the transport properties are observed when the magnetic field is applied along the orthorhombic b and c axes, i.e., perpendicular to the chain direction. Refinements on the single-crystal x-ray diffraction and the measurements of energy dispersive spectroscopy reveal the presence of noticeable Te vacancies in the CVT samples, while the Flux samples are close to the stoichiometry. Analyses on the magnetotransport properties confirm that the carrier densities of the CVT sample are about two orders higher than those of the Flux sample. Our results thus indicate that the widely observed anomalous transport behaviors in pentatellurides actually take place in the Te-deficient samples. For the stoichiometric pentatellurides, our electronic structure calculations show narrow-gap semiconducting behavior, with different transport anisotropies for holes and electrons. For the degenerately doped n-type samples, our transport calculations can result in a resistivity peak and crossover in thermopower from negative to positive at temperatures close to those observed experimentally due to a combination of bipolar effects and different anisotropies of electrons and holes. Our present work resolves the long-standing puzzle regarding the anomalous transport behaviors of pentatellurides, as well as the electronic structure in favor of a semiconducting state.

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The Crystal Structure of HfTe5.

Cited by 125 publications

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Coexistence of topological Dirac fermions on the surface and three-dimensional Dirac cone state in the bulk of ZrTe5 single crystal

Coexistence of topological Dirac fermions on the surface and three-dimensional Dirac cone state in the bulk of ZrTe5 single crystal

Ultrafast Optical Control of the Electronic Properties ofZrTe5

Bipolar Conduction as the Possible Origin of the Electronic Transition in Pentatellurides: Metallic vs Semiconducting Behavior

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