Controlling Multi-band Quantum Materials by Orbital Manipulation


Funded by: Ministero dell’Istruzione, Università e Ricerca (MIUR)  
Calls: PRIN 2015
Start date: 2017-02-05  End date: 2020-02-04
Total Budget: EUR 543.276,00  INO share of the total budget: EUR 115.000,00
Scientific manager: Massimo Capone   and for INO is: Catani Jacopo

Organization/Institution/Company main assignee: Scuola Internazionale Superiore di Studi Avanzati di TRIESTE

other Organization/Institution/Company involved:

other INO’s people involved:

Abstract: Many materials of great scientific and technological interest have an intrinsically multi-orbital electronic structure which leads to a variety of remarkable phenomena. The iron-based superconductors, in which all the five d-orbitals are relevant, are perhaps the most popular example.
In a different field, the developments in the handling of two-electron atoms allowed to simulate multi-orbital physics using ultracold atoms providing us with a tunable and controlled version of the solid state systems.
The aim of the project is to understand and control the properties of multicomponent systems, identifying general concepts and operative protocols to control the electronic properties and induce phase transitions.
We attack this broad problem with a collaborative effort in which different theoretical and experimental methodologies are intertwined.
The key idea is that, by manipulating the occupation of different orbitals, we can change the conduction properties of the systems inducing metal-insulator transitions and orbital-selective Mott states where only the electrons in some orbitals are localized.
The control of the orbital occupation can be realized by laser manipulation, by suitable nanostructuring or, more conventionally by doping or by applying pressure.
These ideas will be tested on some of the most correlated members of the family, AFe2As2 and A1-xFe2-ySe2.
The induced changes in the conduction state reflect on the functional properties of the materials, including superconductivity, magnetism and nematicity in iron-based materials.
A close feedback between experiments assessing the degree of correlation and theoretical calculations combining density-functional theory with many-body methods like Dynamical Mean-Field Theory will be essential to identify the key control parameters to favor one or another phase.
The information about solid-state systems will be complemented by the study of ultracold gases of 173Yb atoms.
These systems can simulate multi-orbital configurations in a direct way tuning with un unprecedented freedom control parameters including dimensionality, hopping elements, effective interaction strength and exchange.
Last, but not least, the orbital population can be controlled allowing for a direct test and a simpler interpretation of the ideas developed for iron-based superconductors.
Using these quantum simulators we will explore the potential of two-orbital superfluidity beyond the limitations of actual materials.
This will allow to identify, through joint theoretical and experimental analysis, the key conditions to optimize the critical temperature which can, in turn, be used to establish the protocols to design high temperature solid state superconductors.
The general ideas developed in the project can be used in a broader framework to understand and control other multi-orbital systems with different functionalities, including multiferroics, thermoelectrics and many others.

INO’s Experiments/Theoretical Study correlated:
Quantum Simulation and Information with degenerate Yb atoms