Project

ARPES; low-dimensional; strong correlations; electronic properties; new materials; quantum matter

Lead
Ci proponiamo di utilizzare due tecniche spettroscopiche avanzate -- la fotoemissione (ARPES) e lo scattering risonante inelastico di raggi X (RIXS) -- per studiare le proprietà elettroniche di varie famiglie di nuovi materiali. Tra questi, metalli non convenzionali e a bassa dimensionalità, superconduttori e sistemi con proprietà magnetiche inusuali. Questi materiali sono interessanti per ragioni fondamentali, ma anche in vista di future applicazioni pratiche.
Lay summary
Questo progetto si propone lo studio della struttura electtronica di varie forme di “materiali quantistici”, cioè di sistemi in cui gli effetti quantistici, al di là dell'immagine usuale di particelle indipendenti, determinano proprietà fisiche nuove e inattese. Di questa classe di materiali fanno parte ad esempio gli isolanti topologici, i sistemi magnetici di tipo “Rashba”, materiali a forti correlazioni elettroniche quali alcuni composti dei metalli di transizione e delle terre rare, e materiali in cui gli elettroni interagiscono fortemente con il reticolo degli ioni. Particolare enfasi sarà data allo studio di materiali a bassa dimensionalità, che spesso conducono alla formazione di nuove fasi ordinate, quali onde di densità di carica o di spin, o fasi isolanti di Mott. Questo studio sarà effettuato utilizzando principalmente la fotoemissione (ARPES) ad alta risoluzione. La ricerca sarà condotta in parte all'EPFL, dove disponiamo di uno spettrometro con caratteristiche avanzate.  Per altri esperimenti di ARPES utilizzeremo la luce di sincrotrone, che offre notevoli vantaggi in termini de polarizzazione e accordabilità. La luce di sincrotrone sarà usata anche in misure assorbimento (XAS) e di diffusione risonante (RIXS) di raggi X, in grado di fornire informazioni complementari sulla struttura elettronica. L'obiettivo di questa ricerca è una migliore conoscenza delle proprietà microscopiche dei materiali quantistici, necessaria per comprendere come proprietà fisiche nuove e potenzialmente utili possano emergere dalle interazioni fondamentali. Una tale comprensione è indispensabile per poter progettare nuovi materiali in grado di realizzare specifiche funzioni.

Direct link to Lay Summary

Last update: 27.09.2013

Lead
We will use two advanced spectroscopic tools -- angle resolved photoelectron spectroscopy (ARPES) and resonant inelastic x-ray scattering (RIXS) -- to study the electronic properties of various classes of new materials such as low-dimensional and unconventional conductors and superconductors and systems with unusual magnetic properties. These materials are of interest for fundamental reasons and also as possible building blocks for future practical applications.
Lay summary
With this research project we address the electronic structure of various forms of quantum matter, i.e. of systems where quantum effects, beyond the usual independent particle picture, determine new and unconventional physical properties. They include novel electronic materials such as topological insulators and Rashba systems, strongly correlated materials such as transition metal or lanthanide compounds, and materials characterized  by a strong coupling between the electrons and the lattice. We put special emphasis on the study of materials with reduced dimensionality, which are especially prone to develop instabilities to interesting broken-symmetry phases, e.g. charge or spin-density-waves, or Mott insulating phases. We investigate these systems by high energy spectroscopies, primarily angle-resolved photoelectron spectroscopy (ARPES) with high energy and momentum resolution. Part of our research will be performed at EPFL, exploiting our state-of-the-art electron spectrometer. We will also perform, at various laboratories worlwide, ARPES experiments with synchrotron radiation, which offers notable advantages in terms of energy tunability and polarization control. At synchrotron radiation facilities we also perform experiments with different spectroscopic techniques, namely x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS), that provide complementary information on the electronic structure of materials. Our goal is to gain a deeper understanding of the microscopic properties of these quantum materials, which will help elucidate the emergence of new, exciting and potentially useful properties, out of the underlying fundamental interactions. Such understanding is crucial to design and develop new materials which realize specific functions.

Direct link to Lay Summary

Last update: 27.09.2013

Number	Title	Start	Funding scheme

With this proposal we seek the renewal of the grant which supports research on the electronic properties of novel materials and artificial structures at the Laboratory of Electron Spectroscopy (LSE) of the Institute of Condensed Matter Physics (ICMP-EPFL). This grant covers the operation of the in-house laboratory, and the related synchrotron radiation activities. It supports one post-doc and two PhD positions.Research at LSE traditionally addresses the electronic structure of various forms of quantum matter, i.e. of systems where quantum effects, beyond the usual independent particle picture, determine most physical properties. They include novel electronic materials such as topological insulators and Rashba systems, strongly correlated materials such as transition metal or lanthanide compounds, and materials characterized by a strong coupling between the electrons and the lattice. We put special emphasis on the study of materials with reduced dimensionality, which are especially prone to develop instabilities to interesting broken-symmetry phases, e.g. charge or spin-density-waves, or Mott insulating phases. We investigate these systems by high energy spectroscopies, primarily angle-resolved photoelectron spectroscopy (ARPES) with high energy and momentum resolution. The LSE runs a state-of-the-art ARPES spectrometer equipped with cryogenic capabilities and ancillary characterization techniques. We also regularly perform ARPES experiments with synchrotron radiation, which offers notable advantages in terms of energy tunability and polarization control. At synchrotron radiation facilities we also perform experiments with different spectroscopic techniques, namely x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS), that provide complementary information on the electronic structure.Our work critically depends on the availability of high-quality crystalline samples. In this respect, the long-standing collaboration with the prominent crystal growth laboratory (H. Berger, A. Magrez) of our Institute, specialized in the synthesis of novel materials, is a very important asset. Some other phases are not easily obtained as single crystals, or only exist as thin films. We have developed the expertise to grow in situ thin film samples and ordered interfaces for spectroscopic investigations. This capability also allows us to study specific physical effects - e.g. the Rashba effect - occurring at surfaces and interfaces. Artificial surface and interface structures also often enable a better control over important parameters such as the lattice spacing, the overlayer-substrate interaction, the band filling, than bulk systems. The Institute of Condensed Matter Physics of the EPFL provides a very favorable environment for our research. We have ongoing collaborations with the experimental groups of H. Brune (STM/STS), L. Forro (transport), H. Ronnow (neutrons, magnetism) and, more recently, of J. Chang (neutrons, ARPES). As a result, a whole range of complementary probes can be applied to the same physical problem. We also take advantage of fruitful collaborations with the theory groups of O. Yazyev (DFT calculations) and F. Mila (strong correlations).Two international collaborations are especially relevant: i) with E. Rotenberg and former LSE member L. Moreschini (ALS, Berkeley) for advanced ARPES synchrotron experiments, including the in-situ growth of thin film samples by pulsed laser deposition; ii) with F. Parmigiani and former LSE member A. Crepaldi (Elettra, Trieste) for time-resolved ARPES experiments.In order to sustain the momentum of our research program, we seek:- the continuation of one post-doc position. This is the only senior position within the group, besides the main applicant. The postdoc plays an essential role in the day-by-day implementation of the research program and supervision of the graduate students. - the continuation of two PhD student positionsInvolved Scientists: Prof. M. Grioni, Dr. Cédric Tournier-Colletta (postdoc), Mr. Simon Moser, Mr. Jens Christian Johannsen;