Université de Fribourg

Uniaxial strain-induced phase transition in the 2D topological semimetal IrTe2

Nicholson, Christopher W. ; Rumo, Maxime ; Pulkkinen, Aki ; Kremer, Geoffroy ; Salzmann, Björn ; Mottas, Marie-Laure ; Hildebrand, Baptiste ; Jaouen, Thomas ; Kim, Timur K. ; Mukherjee, Saumya ; Ma, KeYuan ; Muntwiler, Matthias ; von Rohr, Fabian O. ; Cacho, Cephise ; Monney, Claude

In: Communications Materials, 2021, vol. 2, no. 1, p. 25

Strain is ubiquitous in solid-state materials, but despite its fundamental importance and technological relevance, leveraging externally applied strain to gain control over material properties is still in its infancy. In particular, strain control over the diverse phase transitions and topological states in two-dimensional transition metal dichalcogenides remains an open challenge. Here, we...

Université de Fribourg

Unveiling the complete dispersion of the giant Rashba split surface states of ferroelectric α−GeTe(111) by alkali doping

Kremer, Geoffroy ; Jaouen, Thomas ; Salzmann, Björn ; Nicolaï, L. ; Rumo, Maxime ; Nicholson, Christopher W. ; Hildebrand, Baptiste ; Dil, J. Hugo ; Springholz, G. ; Krempasky, Juraj ; Monney, Claude

In: Physical Review Research, 2020, vol. 2, no. 3, p. 033115

α−GeTe(111) is a noncentrosymmetric ferroelectric material for which a strong spin- orbit interaction gives rise to giant Rashba split states in the bulk and at the surface. The detailed dispersions of the surface states inside the bulk band gap remains an open question because they are located in the unoccupied part of the electronic structure, making them inaccessible to static...

Université de Fribourg

Unveiling the Semimetallic Nature of 1$T$-TiSe$_2$ by Doping its Charge Density Wave

Jaouen, Thomas ; Rumo, Maxime ; Hildebrand, Baptiste ; Mottas, Marie-Laure ; Nicholson, Christopher W. ; Kremer, Geoffroy ; Salzmann, Björn ; Vanini, Fabiano ; Barreteau, C. ; Giannini, E. ; Beck, Hans-Peter ; Aebi, Philipp ; Monney, Claude

The semimetallic or semiconducting nature of the transition metal dichalcogenide 1$T$-TiSe$_2$ remains under debate after many decades mainly due to the fluctuating nature of its 2 x 2 x 2 charge-density-wave (CDW) phase at room- temperature. In this letter, using angle-resolved photoemission spectroscopy, we unambiguously demonstrate that the 1$T$-TiSe$_2$ normal state is semimetallic with ...

Université de Fribourg

Ultrafast dynamics of the surface photovoltage in potassium-doped black phosphorus

Kremer, Geoffroy ; Rumo, Maxime ; Yue, Changming ; Pulkkinen, Aki ; Nicholson, Christopher W. ; Jaouen, Thomas ; Von Rohr, Fabian ; Werner, Philipp ; Monney, Claude

In: Physical Review B, 2021, vol. 104, no. 3, p. 035125

Black phosphorus is a quasi-two-dimensional layered semiconductor with a narrow direct band gap of 0.3 eV. A giant surface Stark effect can be produced by the potassium doping of black phosphorus, leading to a semiconductor to semimetal phase transition originating from the creation of a strong surface dipole and associated band bending. By using time- and angle-resolved photoemission ...

Université de Fribourg

Insensitivity of the striped charge orders in ${\mathrm{IrTe}}_{2}$ to alkali surface doping implies their structural origin

Rumo, Maxime ; Pulkkinen, Aki ; Salzmann, Björn ; Kremer, Geoffroy ; Hildebrand, Baptiste ; Ma, Keyan ; von Rohr, Fabian ; Nicholson, Christopher W. ; Jaouen, Thomas ; Monney, Claude

In: Physical Review Materials, 2021, vol. 5, no. 7, p. 074002

We present a combined angle-resolved photoemission spectroscopy and low-energy electron diffraction (LEED) study of the prominent transition metal dichalcogenide IrTe2 upon potassium (K) deposition on its surface. Pristine IrTe2 undergoes a series of charge-ordered phase transitions below room temperature that are characterized by the formation of stripes of Ir dimers of different...

Université de Fribourg

Nature of native atomic defects in ${\mathrm{ZrTe}}_{5}$ and their impact on the low-energy electronic structure

Salzmann, Björn ; Pulkkinen, Aki ; Hildebrand, Baptiste ; Jaouen, Thomas ; Zhang, S. N. ; Martino, E. ; Li, Q. ; Gu, G. ; Berger, Helmuth ; Yazyev, O. V. ; Akrap, Ana ; Monney, Claude

In: Physical Review Materials, 2020, vol. 4, no. 11, p. 114201

Over the past decades, investigations of the anomalous low-energy electronic properties of ZrTe5 have reached a wide array of conclusions. An open question is the growth method's impact on the stoichiometry of ZrTe5 samples, especially given the very small density of states near its chemical potential. Here we report on high- resolution scanning tunneling microscopy and spectroscopy...

Université de Fribourg

Misfit layer compounds: a platform for heavily doped 2D transition metal dichalcogenides

Leriche, Raphaël T. ; Palacio‐Morales, Alexandra ; Campetella, Marco ; Tresca, Cesare ; Sasaki, Shunsuke ; Brun, Christophe ; Debontridder, François ; David, Pascal ; Arfaoui, Imad ; Šofranko, Ondrej ; Samuely, Tomas ; Kremer, Geoffroy ; Monney, Claude ; Jaouen, Thomas ; Cario, Laurent ; Calandra, Matteo ; Cren, Tristan

In: Advanced Functional Materials, 2020, p. 2007706

Transition metal dichalcogenides (TMDs) display a rich variety of instabilities such as spin and charge orders, Ising superconductivity, and topological properties. Their physical properties can be controlled by doping in electric double‐layer field‐effect transistors (FET). However, for the case of single layer NbSe2, FET doping is limited to ≈1 × 1014 cm−2, while a somewhat larger...

Université de Fribourg

Carbon‐assisted stable silver nanostructures

Abdollahi, S. Narjes ; Ochoa Martínez, Efraín ; Kilchoer, Cédric ; Kremer, Geoffroy ; Jaouen, Thomas ; Aebi, Philipp ; Hellmann, Tim ; Mayer, Thomas ; Gu, Yibei ; Wiesner, Ulrich B. ; Steiner, Ullrich ; Wilts, Bodo D. ; Gunkel, Ilja

In: Advanced Materials Interfaces, 2020, vol. 7, no. 23, p. 2001227

Nanostructured silver stands out among other plasmonic materials because its optical losses are the lowest of all metals. However, nanostructured silver rapidly degrades under ambient conditions, preventing its direct use in most plasmonic applications. Here, a facile and robust method for the preparation of highly stable nanostructured silver morphologies is introduced. 3D nanostructured...

Université de Fribourg

Examining the surface phase diagram of ${\mathrm{IrTe}}_{2}$ with photoemission

Rumo, Maxime ; Nicholson, Christopher W. ; Pulkkinen, Aki ; Hildebrand, Baptiste ; Kremer, Geoffroy ; Salzmann, Björn ; Mottas, Marie-Laure ; Ma, K. Y. ; Wong, E. L. ; Man, M. K. L. ; Dani, K. M. ; Barbiellini, B. ; Muntwiler, Matthias ; Jaouen, Thomas ; Rohr, F. O. von ; Monney, Claude

In: Physical Review B, 2020, vol. 101, no. 23, p. 235120

In the transition metal dichalcogenide IrTe2, low-temperature charge-ordered phase transitions involving Ir dimers lead to the occurrence of stripe phases of different periodicities, and nearly degenerate energies. Bulk-sensitive measurements have shown that, upon cooling, IrTe2 undergoes two such first-order transitions to (5×1×5) and (8×1×8) reconstructed phases at Tc1∼280 K and...

Université de Fribourg

Phase separation in the vicinity of Fermi surface hot spots

Jaouen, Thomas ; Hildebrand, Baptiste ; Mottas, Marie-Laure ; Giovannantonio, M. Di ; Ruffieux, Pascal ; Rumo, Maxime ; Nicholson, Christopher W. ; Razzoli, E. ; Barreteau, C. ; Ubaldini, A. ; Giannini, E. ; Vanini, Fabiano ; Beck, Hans ; Monney, Claude ; Aebi, Philipp

In: Physical Review B, 2019, vol. 100, no. 7, p. 075152

Spatially inhomogeneous electronic states are expected to be key ingredients for the emergence of superconducting phases in quantum materials hosting charge-density waves (CDWs). Prototypical materials are transitionmetal dichalcogenides (TMDCs) and among them, 1T-TiSe2 exhibiting intertwined CDW and superconducting states under Cu intercalation, pressure, or electrical gating. Although it...