Publications de Ana Akrap | EPFL Graph Search

Characterization of two electronic subsystems in cuprates through optical conductivity

Neven Barisic, Ana Akrap, Edoardo Martino

Understanding the physical properties of unconventional superconductors as well as of other correlated materials presents a formidable challenge. Their unusual evolution with doping, frequency, and temperature has frequently led to non-Fermi-liquid (non-FL ...

2023

Addressing shape and extent of Weyl cones in TaAs by Landau level spectroscopy

Ana Akrap

TaAs is a prime example of a topological semimetal with two types of Weyl nodes, W-1 and W-2, whose bulk signatures have proven elusive. We apply Landau level spectroscopy to crystals with multiple facets and identify-among other low-energy excitations bet ...

AMER PHYSICAL SOC2022

Synthesis of murunskite single crystals: A bridge between cuprates and pnictides

László Forró, Ana Akrap, Henrik Moodysson Rønnow, Ivica Zivkovic, Edoardo Martino, Davor Tolj, Trpimir Ivsic, Konstantin Semeniuk

Numerous contemporary investigations in condensed matter physics are devoted to high temperature (high-T-c) cuprate superconductors. Despite its unique effulgence among research subjects, the enigma of the high-T-c mechanism still persists. One way to adva ...

ELSEVIER2021

Mahan excitons in room-temperature methylammonium lead bromide perovskites

László Forró, Majed Chergui, Ana Akrap, Endre Horvath, Tania Palmieri, Edoardo Baldini, Márton Kollár

In a seminal paper, Mahan predicted that excitonic bound states can still exist in a semiconductor at electron-hole densities above the insulator-to-metal Mott transition. However, no clear evidence for this exotic quasiparticle, dubbed Mahan exciton, exis ...

Nature Publishing Group2020

Probing intraband excitations in ZrTe5: A high-pressure infrared and transport study

Helmuth Berger, Ana Akrap, Mathieu François Padlewski, Edoardo Martino, Philip Johannes Walter Moll, Matthias Carsten Putzke

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 r ...

2020

Preferential out-of-plane conduction and quasi-one-dimensional electronic states in layered 1T-TaS2

Helmuth Berger, László Forró, Alla Arakcheeva, Ana Akrap, Luka Ciric, Andrea Pisoni, Edoardo Martino, Philip Johannes Walter Moll, Matthias Carsten Putzke, Konstantin Semeniuk

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. ...

2020

Structural Phase Transition and Bandgap Control through Mechanical Deformation in Layered Semiconductors 1T-ZrX2 (X = S, Se)

Helmuth Berger, Oleg Yazyev, Ana Akrap, Edoardo Martino, Michele Pizzochero, Kristians Cernevics, Konstantin Semeniuk

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 ...

AMER CHEMICAL SOC2020

Optical conductivity of the type-II Weyl semimetal TaIrTe4

Ana Akrap, Konstantin Semeniuk

TaIrTe4 is an example of a candidate Weyl type-II semimetal with a minimal possible number of Weyl nodes. Four nodes are reported to exist in a single plane in k space. The existence of a conical dispersion linked toWeyl nodes has yet to be shown experimen ...

AMER PHYSICAL SOC2020

Nature of native atomic defects in ZrTe5 and their impact on the low-energy electronic structure

Helmuth Berger, Oleg Yazyev, Ana Akrap, Shengnan Zhang

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 ...

AMER PHYSICAL SOC2020

Low-energy excitations in type-II Weyl semimetal T-d-MoTe2 evidenced through optical conductivity

Ana Akrap

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 proper ...

AMER PHYSICAL SOC2020

Persistent antiferromagnetic order in heavily overdoped Ca1-xLaxFeAs2

László Forró, Ana Akrap, Henrik Moodysson Rønnow, Ivica Zivkovic, Sergiy Katrych, Edoardo Martino, Philip Johannes Walter Moll, Maja Deborah Bachmann

In the Ca1-xLaxFeAs2 (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 = 12 ...

2019

Two-Dimensional Conical Dispersion in ZrTe5 Evidenced by Optical Spectroscopy

Helmuth Berger, Ana Akrap, Edoardo Martino

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 an ...

AMER PHYSICAL SOC2019

Nonuniform carrier density in Cd3As2 evidenced by optical spectroscopy

Ana Akrap, Edoardo Martino

2018

Electronic properties of incommensurately modulated novel and complex materials

László Forró, Oleg Yazyev, Alla Arakcheeva, Ana Akrap, Gabriel Albert Autes, Sergiy Katrych, Edoardo Martino, Philip Johannes Walter Moll

INT UNION CRYSTALLOGRAPHY2018

BiTeCl and BiTeBr: A comparative high-pressure optical study

Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Oleg Yazyev, Ana Akrap, Gabriel Albert Autes

We here report a detailed high-pressure infrared transmission study of BiTeCl and BiTeBr. We follow the evolution of two band transitions: the optical excitation beta between two Rashba-split conduction bands, and the absorption. across the band gap. In th ...

Amer Physical Soc2017

Crystal Structure, Transport, and Magnetic Properties of an Ir6+ Compound Ba8Al2IrO14

László Forró, Arnaud Magrez, Alla Arakcheeva, Bastien Dalla Piazza, Ana Akrap, Krunoslav Prsa, Henrik Moodysson Rønnow, Jacim Jacimovic, Sergiy Katrych, Andrea Pisoni, Lin Yang

The novel iridate Ba8Al2IrO14 was prepared as single crystals by self-flux method, thereby providing a rare example of an all-Ir(VI) compound that can be synthesized under ambient pressure conditions. The preparation of all-Ir6+ iridate without using tradi ...

2015

Optical properties of BiTeBr and BiTeCl

Helmuth Berger, Philippe Bugnon, Arnaud Magrez, Ana Akrap, Dirk Van der Marel

We present a comparative study of the optical properties-reflectance, transmission, and optical conductivity- and Raman spectra of two layered bismuth-tellurohalides BiTeBr and BiTeCl at 300 and 5 K, for light polarized in the a-b planes. Despite different ...

Amer Physical Soc2014

Infrared- and Raman-Spectroscopy Measurements of a Transition in the Crystal Structure and a Closing of the Energy Gap of BiTeI under Pressure

Oleg Yazyev, Ana Akrap, Gabriel Albert Autes, Dirk Van der Marel

BiTeI is a giant Rashba spin splitting system, in which a noncentrosymmetric topological phase has recently been suggested to appear under high pressure. We investigated the optical properties of this compound, reflectivity and transmission, under pressure ...

American Physical Society2014

Enhanced low-temperature thermoelectrical properties of BiTeCl grown by topotactic method

Helmuth Berger, Philippe Bugnon, László Forró, Richard Gaal, Arnaud Magrez, Ana Akrap, Jacim Jacimovic, Xavier François Mettan, Sergiy Katrych, Andrea Pisoni

We developed a topotactic strategy to grow BiTeCl single crystals. Structural characterization by means of X-ray diffraction was performed, and the high crystallinity of the material was proven. Measurements of the thermoelectrical coefficients electrical ...

Pergamon-Elsevier Science Ltd2014

Bi2Te3-xSex series studied by resistivity and thermopower

László Forró, Ana Akrap

We study the detailed temperature and composition dependence of the resistivity, rho(T), and thermopower, S(T), for a series of layered bismuth chalcogenides Bi2Te3-xSex, and report the stoichiometry dependence of the optical band gap. In the resistivity o ...

IOP Publishing - EPL Association2014