Thursday July 18 at 2 PM
ISMO amphitheater
Electronic structure of quantum materials: searching for signatures of correlations
For the past sixty years, strongly correlated electron systems have drawn scientific interest in condensed matter physics. They exhibit new exotic states as well as intrinsic many-body properties. Using angle-resolved photoemission spectroscopy (ARPES), one can disentangle, by measuring the electronic structure of these materials, the contributions of electronic, structural and magnetic degrees of freedom. ARPES is therefore an indispensable technique in order to understand and explain the effects of correlations in crystals. In this work, the electronic structures of three different types of materials have been studied by means of ARPES:
The new family of 1142 and 122 compounds: The crystal structure (of the type AlGe for the 1142s or AlGe for the 122s, where = Sm, Tb, Gd and = Au, Ni) of these materials is composed of triangular-net arrangements of lanthanide elements, which carry the magnetic properties of the crystal. This specific configuration induces magnetic frustration, which results in complex magnetic structures and magnetic phase transitions. Moreover, these structures are embedded among transition metal elements, interesting for possible correlation effects.
Copper sulfide CuS, also known as covellite, is the first discovered natural mineral superconductor. Surprisingly, this compound hosts similar properties to high- superconductors containing Cu, known as cuprates. Moreover, CuS presents a structural phase transition at = 55 K. By combining theoretical and experimental (DFT and ARPES) investigations, we reveal the signatures of the phase transition in the electronic structure of CuS.
Vanadium dioxide VO is still the subject of a fifty-year-long controversy concerning the origin of its metal-to-insulator transition at 340 K. Upon the transition, the V chains dimerize, which is the signature of a Peierls-like mechanism. On the other hand, it has been shown that VO is a strongly correlated system, in which correlations, induced by the strong coulomb forces, localize the conduction electrons and play an essential role in the electronic transition. It is today now commonly accepted that the two mechanisms assist each other to trigger the transition.
Link :
https://cnrs.zoom.us/j/97946555762?pwd=nJLlvZtZ0gb1jMQe3xL3qf0UXdU2rT.1