Laboratory of Theoretical and Experimental Superconductive Tunnelling

Giovanni Alberto Cesare Ummarino

Address	Department of Applied Science and Technology, Politecnico di Torino corso Duca degli Abruzzi 24, 10129 Torino (TO) - Italy
Telephone:	+39 011 090 7313 (office)
Fax:	+39 011 090 7399
E-mail address	giovanni.ummarino_at_infm.polito.it

Present position

Assistant Professor

Work and research experience

From	To
2000	2003	Researcher of the Italian National Institute for the Physics of Matter (INFM) -  research in theory of superconductivity
1997	1999	Post-doc fellowship at Politecnico di Torino -  research in theory of superconductivity
1994	1996	PhD in Physics at Politecnico di Torino - research in theory of superconductivity
1992	1993	Scholarship at “Istituto Elettrotecnico Nazionale Galileo Ferraris” (Torino) - research on magnetic properties of materials, prof Giorgio Bertotti
1990	1991	Teacher of Mathematics and Physics in high schools and research collaboration with Turin University in the field of General Relativity

Education

1997	PhD in Physics Politecnico di Torino
1989	Master Degree in Physics Università di Torino

Affiliation to Scientific Societies or Associations or
Institutes

Since 2005
Affiliated to the “Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia” (CNISM)

From 1998 to 2004
Affiliated to the Italian Institute for the Physics of Matter (INFM)

Summary of Research Activity

- Theoretical activity in the field of condensed matter physics and in particular superconductivity

- Numerical solution of complex integral-differential coupled equations and related technicalities

- Interpretation of experimental data from point-contact spectroscopy, specific-heat measurements, resistivity measurements, microwave absorption, etc. within different theories for superconductivity (e.g. BCS, Eliashberg, Ginzburg-Landau)

In more detail,  my specific research includes:

1) Theoretical and experimental study high-temperature superconductors (Bi₂Sr₂Ca₂CO_8-x, La_2-xSr_xCuO_4-x, YBa₂Cu3O_7-x, RuSr₂GdCu₂O₈) by means of tunnel spectroscopy and Josephson spectroscopy

2) Solution of the Eliashberg equations in the imaginary-axis and real-axis formulations, generalized to the case of:

- different symmetries of the order parameter (s,d, s+d, d+id and so on);

- finite bandwidth;

- non half filling;

- non constant normal density of state

-breakdown of the Migdal theorem

-multiband case

3) Theoretical study of other superconducting systems like borocarbides (YNi₂B₂C), fullerene (C60, Rb₃C₆₀), zirconium dodecaboride (ZrB₁₂) and comparison with experimental data from tunnel and point-contact spectroscopies.

4) Extended theoretical study of two-band superconductivity in magnesium diboride (MgB₂), in particular:

- Study of the effects of chemical doping with Al and C on the critical temperature and the  gaps, and comparison of the results with experimental data from point-contact  spectroscopy and specific-heat measurements

- study of the effects of magnetic impurities (Mn) on the spin-flip scattering channels  (intraband and interband) and consequent effects on the values of the order parameters

- study of the magnetic penetration length from measurements of microwave absorption in thin films

5) Theoretical study on mechanism of superconductivity in radioactive material PuCoGa5 and NpPdAl5

6) Theoretical study on mechanism of superconductivity in new iron-arsenides based materials

7) General Relativity.

Supervision of PhD Students

2012-2014
Generalization of the Eliashberg equations and Density Functional Theory applied to the analysis of the fundamental properties of iron-based superconductors
(Sara Galasso)

Publications

The aforementioned research has led to about 110 publications international journals, cited about 1200 times (sources: Web of Science, Scopus: updated to Jan 2015)

List of publications (archive of Politecnico di Torino)

LaTEST - Department of Applied Science and Technology, Politecnico di Torino
corso Duca degli Abruzzi 24, 10129 Torino (TO) - Italy