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

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

Superconducting and antiferromagnetic properties of dual-phase V3Ga

Jamer, Michelle E. ; Wilfong, Brandon ; Buchelnikov, Vasiliy D. ; Sokolovskiy, Vladimir V. ; Miroshkina, Olga N. ; Zagrebin, Mikhail A. ; Baigutlin, Danil R. ; Naphy, Jared ; Assaf, Badih A. ; Lewis, Laura H. ; Pulkkinen, Aki ; Barbiellini, Bernardo ; Bansil, Arun ; Heiman, Don

In: Applied Physics Letters, 2020, vol. 117, no. 6, p. 062401

The binary compound V3Ga can exhibit two near-equilibrium phases, the A15 structure that is superconducting and the Heusler D03 structure that is semiconducting and antiferromagnetic. Density functional theory calculations show that these two phases are nearly degenerate, being separated in energy by only ±10 meV/atom. Our magnetization measurements on bulk-grown samples show ...

Université de Fribourg

Mapping the unoccupied state dispersions in ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ with resonant inelastic x-ray scattering

Monney, Claude ; Herzog, Marc ; Pulkkinen, Aki ; Huang, Y. ; Pelliciari, Jonathan ; Olalde-Velasco, P. ; Katayama, Naoyuk ; Nohara, Minoru ; Takagi, Hide ; Schmitt, Thorsten ; Mizokawa, Takashi

In: Physical Review B, 2020, vol. 102, no. 8, p. 085148

The transition metal chalcogenide Ta2NiSe5 undergoes a second-order phase transition at Tc=328K involving a small lattice distortion. Below Tc, a band gap at the center of its Brillouin zone increases up to about 0.35 eV. In this work, we study the electronic structure of Ta2NiSe5 in its low-temperature semiconducting phase, using resonant inelastic x-ray scattering (RIXS) at the Ni L3 edge....

Université de Fribourg

Electronic structure beyond the generalized gradient approximation for ${\mathrm{Ni}}_{2}\mathrm{MnGa}$

Baigutlin, D. R. ; Sokolovskiy, V. V. ; Miroshkina, O. N. ; Zagrebin, M. A. ; Nokelainen, J. ; Pulkkinen, Aki ; Barbiellini, B. ; Pussi, K. ; Lähderanta, E. ; Buchelnikov, V. D. ; Zayak, A. T.

In: Physical Review B, 2020, vol. 102, no. 4, p. 045127

The stability of the nonmodulated martensitic phase, the austenitic Fermi surface, and the phonon dispersion relations for ferromagnetic Ni2MnGa are studied using density functional theory. Exchange-correlation effects are considered with various degrees of precision, starting from the simplest local spin density approximation (LSDA), then adding corrections within the generalized gradient...

Université de Fribourg

Ab initio description of the ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+{\delta}}$ electronic structure

Nokelainen, Johannes ; Lane, Christopher ; Markiewicz, Robert S. ; Barbiellini, Bernardo ; Pulkkinen, Aki ; Singh, Bahadur ; Sun, Jianwei ; Pussi, Katariina ; Bansil, Arun

In: Physical Review B, 2020, vol. 101, no. 21, p. 214523

Bi-based cuprate superconductors are important materials for both fundamental research and applications. As in other cuprates, the superconducting phase in the Bi compounds lies close to an antiferromagnetic phase. Our density functional theory calculations based on the strongly-constrained-and- appropriately-normed exchange correlation functional in ...

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...