Laboratory for Topological Matter

Topology at Bad Ragartz 2009
(Linea del Tempo continuo · Silvio Santini)

In the Laboratory for Topological Matter we study the influence of topology on the electronic structure, magnetic properties, and phase transitions. The studies systems include, among others, various types of topological insulators, Dirac, Weyl and related semimetals, skyrmions, transition metal oxides, and multiferroic materials. The topological properties are investigated using a variety of photon-based spectroscopic techniques such as ARPES and RIXS both at the Swiss Light Source of the Paul Scherrer Institute and at the LACUS laser facility at the EPFL. Special attention is paid to the reciprocal space spin textures of materials and the possibility to actively influence these.

Fermi surface of the TI PbBi4Te7 with spin texture and spindle torus Fermi surface of BiTeI
Dispersion of a TI and Rashba-Zeeman system © H. Dil 2020 EPFL

A single helix for novel quantum phenomena

— By growing thin films of SrTiO3 on thick wafers of the same material, researchers from the EPFL and PSI have been able to create a 2D electron gas that shows just one single spin component at the Fermi surface.

Crystal structures with opposite chirality © Schröter 2020 PSI

Cherned up to the maximum

— In topological materials, electrons can display behaviour that is fundamentally different from that in ‘conventional’ matter, and the magnitude of many such ‘exotic’ phenomena is directly proportional to an entity known as the Chern number. New experiments establish for the first time that the theoretically predicted maximum Chern number can be reached — and controlled — in a real material.

Magnetic domain pattern of Fe3Sn2 single crystals © G. Aeppli 2020 EPFL

Images of a first order phase transition in a Weyl ferromagnet

— A new publication from the group describes magnetic images and susceptibility data exploring the coexistence of two distinct topological states in the Kagomé ferromagnet Fe3Sn2.

© H. Dil 2019 EPFL

Mauro Fanciulli receives Physics Doctoral Thesis Award

— We are very proud to announce that Mauro Fanciulli received the doctoral thesis award of the physics section for his thesis entitled ‘Spin polarization and attosecond time delay in photoemission from solids’

An illustration of the effect discovered in this study (credit: A. Weber/EPFL)

A dynamic material with a polar shell

— A new study shows that the phase transitions of the exotic material molybdenum ditelluride – a candidate for future electronics – are more complex than previously thought.

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