Université de Fribourg

Structural phase transition and bandgap control through mechanical deformation in layered semiconductors 1T–ZrX2 (X = S, Se)

Martino, Edoardo ; Santos-Cottin, David ; Le Mardelé, Florian ; Semeniuk, Konstantin ; Pizzochero, Michele ; Čerņevičs, Kristia̅ns ; Baptiste, Benoît ; Delbes, Ludovic ; Klotz, Stefan ; Capitani, Francesco ; Berger, Helmuth ; Yazyev, Oleg V. ; Akrap, Ana

In: ACS Materials Letters, 2020, vol. 2, no. 9, p. 1115–1120

Applying elastic deformation can tune a material’s physical properties locally and reversibly. Spatially modulated lattice deformation can create a bandgap gradient, favoring photogenerated charge separation and collection in optoelectronic devices. These advantages are hindered by the maximum elastic strain that a material can withstand before breaking. Nanomaterials derived by exfoliating...

Université de Fribourg

Low-energy excitations in type-II Weyl semimetal ${T}_{d}\text{\ensuremath{-}}{\mathrm{MoTe}}_{2}$ evidenced through optical conductivity

Santos-Cottin, David ; Martino, Edoardo ; Le Mardelé, Florian ; Witteveen, C. ; Rohr, F. O. von ; Homes, C. C. ; Rukelj, Z. ; Akrap, Ana

In: Physical Review Materials, 2020, vol. 4, no. 2, p. 021201

Molybdenum ditelluride, MoTe2, is a versatile material where the topological phase can be readily tuned by manipulating the associated structural phase transition. The fine details of the band structure of MoTe2, key to understanding its topological properties, have proven difficult to disentangle experientially due to the multiband character of the material. Through experimental optical...

Université de Fribourg

Persistent antiferromagnetic order in heavily overdoped Ca1-x La x FeAs2

Martino, Edoardo ; Bachmann, Maja D ; Rossi, Lidia ; Modic, Kimberly A ; Zivkovic, Ivica ; Rønnow, Henrik M ; Moll, Philip J W ; Akrap, Ana ; Forró, László ; Katrych, Sergiy

In: Journal of Physics: Condensed Matter, 2019, vol. 31, no. 48, p. 485705

In the Ca1−x La x FeAs2 (1 1 2) family of pnictide superconductors, we have investigated a highly overdoped composition (x = 0.56), prepared by a high-pressure, high-temperature synthesis. Magnetic measurements show an antiferromagnetic transition at T N = 120 K, well above the one at lower doping (0.15 < x < 0.27).Below the onset of long-range...

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...

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4 Martino, E.