José Lorenzana
I am a Senior Researcher at the Institute for Complex Systems, CNR. My main interest is complex solids intended as materials in which different phases compete producing interesting collective behavior. Competition arises because interactions and the kinetic energy contribute similarly to the energy, therefore complex solids are nor in the weak nor in the strong coupling regime which makes them difficult to treat with conventional perturbative approaches. Competition between phases often leads to gigantic responses to external perturbations which make complex solids interesting for applications.
Also, competition between long-range and short-range forces often leads to inhomogeneous states as in the familiar example of domain formation in ferromagnets. In electronic systems, one interesting way to become inhomogeneous, which I have studied in the last years, is Coulomb frustrated phase separation. Elastic forces in solids are not screened and lead to a similar phenomenology and interesting thermodynamic anomalies as in the case of the volume collapse in mixed valence compounds.
Some complex solids respond magnetically to an electric field or electrically to a magnetic field. This behavior is called multiferroic. With George Sawatzky, I have developed a theory of dipole light absorption by magnetic excitations assisted by phonons. More recently I contributed to the theory of the high-Tc multiferroic effect in CuO and showed how the disorder can improve the multiferroic properties by a mechanism called order by disorder.
Goetz Seibold and I have developed a time-dependent extension of the Gutzwiller approximation, which is a nonperturbative technique well suited to treat strongly correlated systems even when they become inhomogeneous. We have used this approach to computing collective excitations of nanostructured cuprates. Other applications have involved the magnetic phases of the Hubbard model and Auger spectroscopy.
We have not a satisfactory ab initio understanding of strongly correlated systems as we have for wide-band materials. The failure in Mott systems has been put on rigorous grounds. I suggested that a non-local density functional inspired on the Gutzwiller approximation should solve some of the problems.
Barbara Mansart, Fabrizio Carbone and collaborators have shown that a high-Tc superconducting condensate can be put out of equilibrium and oscillate at a frequency given by twice the superconducting gap. In collaboration with them, we have developed the theory of this phenomenon and a new technique called coherent charge fluctuation spectroscopy which allows identifying bosonic excitations coupled to superconducting quasiparticles potentially involved in pairing. A more recent development with Ojeda Collado, Usaj and Balseiro involves inducing Rabi oscillations in the condensate with a periodic drive and time crystal phases.
After many years of studying high-Tc superconductors, I have been captured by the advent of the iron age of superconductivity. We predicted early an exotic magnetic phase that competes with superconductivity and which later has been experimentally reported. The phase diagram as a function of doping is remarkably similar to our prediction in a related compound. Together with Wojciech Grochala and his group, we are presently exploring a possible future Silver age. With Maria N. Gastiasoro and many collaborators in Rome we have revisited the problem of superconductivity in incipient ferroelectrics.
Present Postdocs
Adrian Gomez Pueyo
Former Postdocs
Johan Hellsvik (now researcher at Stockholm).
Valentina Brosco (now researcher at ISC).
Zujian Ying (now professor at Lanzhou University).
Gabriele Messina (now research scientist at Banca d'Italia).
Maria Navarro Gastiasoro (now at Donostia International Physics Center)
Hector Pablo Ojeda Collado (now at Hamburg University)
Present Students
Ilya Degtev (PhD)
Antonio Santacesarea (PhD)
Former Students
Juan Diego Suarez-Fromm (undergraduate, 8/1996 - 12/1997, Instituto Balseiro). Now at Tecpetrol.
Daniel García (undergraduate, 8/1996 - 12/1997, Instituto Balseiro). Now at Centro Atómico Bariloche.
Carmine Ortix (undergraduate, 9/2002 - 9/2003 and graduate, 9/2002 - 9/2003, Universita` di Roma, “La Sapienza"). Now at Leibniz Institute for Solid State and Materials Research, Dresden
Alessandro Attanasi (undergraduate, 5/2004 - 5/2005 and graduate, 5/2004 - 5/2005, Universita` di Roma, “La Sapienza”). Past: Nergal. Now at PTV Optima group
Andrea Di Ciolo (undergraduate 6/2004-9/2005, and graduate, 6/2004-9/2005, Universita` di Roma, “La Sapienza”). Past: Goethe Universität Frankfurt, Georgetown University. Now at CNR-Nano.
Marcello Balestrieri (undergraduate 07/2010 to 01/2012. Past: SISSA (Trieste).
Nicolò Defenu (undergraduate 03/2012-12/2012). Past: SISSA (Trieste).
Matteo Capati (undergraduate 12/2008-12/2009 and graduate 1/2010 - 3/2014, Universita` di Roma, “La Sapienza”)
Antonio Tramontana (Undergraduate, 03/2014 - 12/2014, Università di Roma, “La Sapienza”) )
Nicolas Mingione (from ESPCI, Paris) (05/2017 - 07/2017, Stage at Università di Roma, “La Sapienza”)
Maria Eleonora Temperini (Stage, 11/2019- 10-2020, ISC-CNR)
Riccardo Piombo (Undergraduate 10/2017-10/2018, and graduate 10/2018 - 5/2022, Università di Roma, “La Sapienza”).
Publications
Edited volume:
Talks
Superconductivity in incipient ferroelectrics for condensed matter folks, and a talk for a broader public in Spanish: Electrones al borde de una crisis de identidad.
Dynamical phase diagram of driven BCS systems
Present Projects
QT-Fluo
Past Projects
Spectroscopy of ordered and quasi-ordered complex solids (SOQCS)
New density functionals for the electronic structure of correlated materials (NEWDFESCM)
Supercondouctors for imaging (SIMAP)
A silver path to a new generation of quantum materials (SilverPath)
Extreme nonlinear dynamics of driven superconductors (SuperDyn)