Category Archives: News

High-Resolution Photoemission on  Sr2RuO4  Reveals Correlation-Enhanced  Spin-Orbit Coupling and Dominantly Local Self-Energies

High-Resolution Photoemission on Sr2RuO4 Reveals Correlation-Enhanced Spin-Orbit Coupling and Dominantly Local Self-Energies

Experiments reveal that quasiparticle properties in the superconductor Sr2RuO4 have a significant angular dependence due to the combined effects of local electron interactions and spin-orbit coupling.

We determine the variation of the mass enhancement along the entire Fermi surface, which shows a strong dependence on the direction of the quasiparticle momentum. This is often interpreted as a signature of nonlocal interactions that are strong at certain momenta and weak at others. However, using a new method to analyze our data, we show that this momentum dependence is apparent only if the problem is described in a momentum-space basis and disappears almost completely when electronic states are described in a basis of local orbitals.

This work is published in Phys. Rev. X.

Microfocus Laser–based Angle-Resolved Photoemission on Encapsulated 1T′-WTe2

Microfocus Laser–based Angle-Resolved Photoemission on Encapsulated 1T′-WTe2

January 2019: We measured the electronic structure of exfoliated mono-, bi-, and few-layer 1T′-WTe2 by laser-based microfocus angle-resolved photoemission. This is achieved by encapsulating with monolayer graphene a flake of WTe2 comprising regions of different thickness. Our data support the recent identification of a quantum spin Hall state in monolayer 1T′-WTe2 and reveal strong signatures of… Continue Reading

In-situ strain tuning of the metal-insulator-transition of Ca2RuO4

In-situ strain tuning of the metal-insulator-transition of Ca2RuO4

October 2018: We studied the evolution of the k-space electronic structure of bulk Ca2RuO4, lightly doped with Pr, under uniaxial strain. Using ultrathin plate-like crystals, we achieve uniaxial strain levels up to−4.1%, sufficient to suppress the insulating Mott phase and access the previously unexplored electronic structure of the metallic state at low temperature. Nature Communications volume 9,… Continue Reading

Out-of-plane spin texture in a SrTiO3(111) 2DEG.

Out-of-plane spin texture in a SrTiO3(111) 2DEG.

We have identified a three-dimensional spin texture in the two-dimensional electron gas (2DEG) at the SrTiO3 (111) surface.  In a free-electron Rashba 2DEG system the induced spin polarization lies entirely in the plane of confinement. Our tight binding supercell calculations for the SrTiO3 (111) 2DEG reveal a Rashba spin-splitting with a significant out-of-plane component in… Continue Reading

Trivial Fermi arcs in the candidate type-II Weyl semimetal WTe2

Trivial Fermi arcs in the candidate type-II Weyl semimetal WTe2

September 2016: Using micro focused laser ARPES we have observed large Fermi arcs on both the top and bottom surface of WTe2. Our surface electronic structure calculations demonstrate that these Fermi arcs are topologically trivial and that their existence is independent of the presence of type-II Weyl points in the bulk band structure. Contrary to common… Continue Reading

Fermi arcs and their topological character in the type-II Weyl semimetal MoTe2

Fermi arcs and their topological character in the type-II Weyl semimetal MoTe2

We published in Phys. Rev. X a combined experimental and theoretical study of MoTe2, which provides new evidence for the existence of type-II Weyl semimetals. Using angle-resolved photoemission, we show that the inequivalent top and bottom (001) surfaces of MoTe2 host distinct Fermi arc surface states. Employing systematic electronic structure calculations, we show that some of these… Continue Reading

Alberto de la Torre receives the “Prix Vacheron Constantin des Sciences 2016”

Alberto de la Torre receives the “Prix Vacheron Constantin des Sciences 2016”

Alberto de la Torre has been awarded the “Prix Vacheron Constantin des Sciences 2016” for his doctoral thesis entitled Spectroscopic Studies of Layered Iridium Oxides and reporting “the doping evolution of the electronic structure of the single and bilayer iridates Sr2IrO4 and Sr3Ir2O7 from angle resolved photoemission (ARPES) experiments”. This prize encourage young students from… Continue Reading

The fate of Fröhlich polarons in SrTiO3 – Nature Materials

The fate of Fröhlich polarons in SrTiO3 – Nature Materials

April 2016: We publish in Nature Materials a study of electron-phonon interactions in the SrTiO3(001) two-dimensional electron liquid. The band insulator strontium titanate, SrTiO3, widely used as substrate for growing oxides films, is a highly fascinating material in its own right. Most notably, it becomes superconducting upon doping with less than 1 excess electron per… Continue Reading

Flavio Bruno has been awarded an Ambizione Fellowship by the SNF

Flavio Bruno has been awarded an Ambizione Fellowship by the SNF

October 2015: Flavio Bruno has been awarded an Ambizione fellowship by the Swiss National Science Foundation. His project will focus on the characterization of the electronic band structure and many-body effects in strongly correlated artificial heterostructure. The objective is to demonstrate that sputtering is an excellent growth method to produce high quality oxide heterostructure with a surface… Continue Reading

Collapse of the Mott gap and emergence of a nodal liquid in lightly doped Sr2IrO4 – in PRL

Collapse of the Mott gap and emergence of a nodal liquid in lightly doped Sr2IrO4 – in PRL

October 2015: We report an ARPES study on the doping evolution of the Heisenberg antiferromagnet Sr2IrO4, a close analogue to underdoped cuprates (Phys. Rev. Lett. 115, 176402 (2015)). Superconductivity in underdoped cuprates emerges from an unusual electronic state characterised by nodal quasiparticles and an antinodal pseudo gap. The relation between this state and superconductivity is intensely studied… Continue Reading

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