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Université de Fribourg

Preferential out-of-plane conduction and quasi-one-dimensional electronic states in layered 1T-TaS 2

Martino, E. ; Pisoni, A. ; Ćirić, L. ; Arakcheeva, A. ; Berger, H. ; Akrap, Ana ; Putzke, C. ; Moll, P. J. W. ; Batistić, I. ; Tutiš, E. ; Forró, László ; Semeniuk, K.

In: npj 2D Materials and Applications, 2020, vol. 4, no. 1, p. 1–9

Layered transition metal dichalcogenides (TMDs) are commonly classified as quasi-two-dimensional materials, meaning that their electronic structure closely resembles that of an individual layer, which results in resistivity anisotropies reaching thousands. Here, we show that this rule does not hold for 1T-TaS2—a compound with the richest phase diagram among TMDs. Although the onset of ...

Université de Fribourg

Probing intraband excitations in ${\mathrm{ZrTe}}_{5}$: A high-pressure infrared and transport study

Santos-Cottin, D. ; Padlewski, M. ; Martino, E. ; David, S. Ben ; Mardelé, F. Le ; Capitani, F. ; Borondics, F. ; Bachmann, M. D. ; Putzke, C. ; Moll, P. J. W. ; Zhong, R. D. ; Gu, G. D. ; Berger, H. ; Orlita, M. ; Homes, C. C. ; Rukelj, Z. ; Akrap, Ana

In: Physical Review B, 2020, vol. 101, no. 12, p. 125205

Zirconium pentatetelluride, ZrTe5, shows remarkable sensitivity to hydrostatic pressure. In this work we address the high-pressure transport and optical properties of this compound, on samples grown by flux and chemical vapor transport. The high-pressure resistivity is measured up to 2 GPa, and the infrared transmission up to 9 GPa. The dc conductivity anisotropy is determined using a...

Université de Fribourg

Two-dimensional conical dispersion in ${\mathrm{ZrTe}}_{5}$ evidenced by optical spectroscopy

Martino, Edoardo ; Crassee, Iris ; Eguchi, Gaku ; Santos-Cottin, David ; Zhong, R. D. ; Gu, G. D. ; Berger, H. ; Rukelj, Zoran ; Orlita, M. ; Homes, Chris C. ; Akrap, Ana

In: Physical Review Letters, 2019, vol. 122, no. 21, p. 217402

Zirconium pentatelluride was recently reported to be a 3D Dirac semimetal, with a single conical band, located at the center of the Brillouin zone. The cone’s lack of protection by the lattice symmetry immediately sparked vast discussions about the size and topological or trivial nature of a possible gap opening. Here, we report on a combined optical and transport study of ZrTe5, which...

Consortium of Swiss Academic Libraries

Infrared signature of the charge-density-wave gap in ZrTe3

Perucchi, A. ; Degiorgi, L. ; Berger, H.

In: The European Physical Journal B - Condensed Matter and Complex Systems, 2005, vol. 48, no. 4, p. 489-493

Consortium of Swiss Academic Libraries

Nonlinear magnetic response in ruthenocuprates

Živković, I. ; Awana, V. P.S. ; Berger, H.

In: The European Physical Journal B, 2008, vol. 62, no. 4, p. 423-431

Consortium of Swiss Academic Libraries

Multiple scattering investigation of the 1T-TaS2 surface termination

Despont, L. ; Clerc, F. ; Garnier, M. G. ; Berger, H. ; Forró, L. ; Aebi, P.

In: The European Physical Journal B - Condensed Matter and Complex Systems, 2006, vol. 52, no. 3, p. 421-426

Université de Fribourg

Dramatic effective mass reduction driven by a strong potential of competing periodicity

Monney, Claude ; Schwier, Eike Fabian ; Garnier, Michael G. ; Battaglia, C. ; Mariotti, N. ; Didiot, Clément ; Cercellier, H. ; Marcus, J. ; Berger, H. ; Titov, A. N. ; Beck, Hans ; Aebi, Philipp

In: Europhysics Letters, 2010, vol. 92, no. 4, p. 47003

We present angle-resolved photoemission experiments on 1T-TiSe₂ at temperatures ranging from 13 K to 288 K. The data evidence a dramatic renormalization of the conduction band below 100 K, whose origin can be related to the new potential responsible for the charge density wave phase at low temperature in this system. The renormalization translates into a substantial effective mass...

Université de Fribourg

Temperature-dependent photoemission on 1T-TiSe₂: Interpretation within the exciton condensate phase model

Monney, Claude ; Schwier, Eike Fabian ; Garnier, Michael G. ; Mariotti, Nicholas ; Didiot, Clément ; Beck, Hans ; Aebi, Philipp ; Cercellier, H. ; Marcus, J. ; Battaglia, C. ; Berger, H.

In: Physical Review B, 2010, vol. 81, no. 15, p. 1551104

The charge-density-wave phase transition of 1T-TiSe₂ is studied by angle-resolved photoemission over a wide temperature range. An important chemical-potential shift which strongly evolves with temperature is evidenced. In the framework of the exciton condensate phase, the detailed temperature dependence of the associated order parameter is extracted. Having a mean-field-like behavior at low...

Université de Neuchâtel

Interplane coupling in the quasi-two-dimensional 1T-TaS2

Bovet, M. ; van Smaalen, S. ; Berger, H. ; Gaal, R. ; Forró, L. ; Schlapbach, Louis ; Aebi, Philipp

In: Physical Review B, 2003, vol. 67, no. 125105, p. 1-5

Density-functional band-structure calculations including atomic displacements in the charge-density wave phase have been performed for the layered 1T-TaS2. This quasi-two-dimensional material exhibits a charge-density wave extending in all three dimensions. We find that the topmost occupied Ta d band is localized in plane but strongly disperses perpendicular to the layers...