Foto del docente

Samuele Sanna

Assistant professor

Department of Physics and Astronomy

Academic discipline: FIS/03 Physics of Matter

Research

My main research interests are focused on the study of Quantum Materials, mainly displaying magnetism and/or superconductivity.

In Matter Physics it has been recently introduced [REF1, REF2] the broad term Quantum Materials to identify materials which display collective quantum phenomena, also called emergent phenomena, emerging from the many-body interaction of different physical entities such as spin, charge, phonon, orbital…

The properties of these materials are uniquely defined by quantum mechanical effects that remain manifest at high temperatures and macroscopic length scales and offer an excellent playground to study fundamental physical phenomena with a high potential for novel technological applications. For example, Quantum Materials can typically display magnetism, superconductivity, superfluidity, topological order, fractional quantum Hall effect, etc.

Research on quantum materials is a multidisciplinary field which brings together scientists working on a variety of problems at the frontiers of physics, materials science, chemistry and engineering.

 

MAIN ONGOING RESEARCH PROJECTS IN BRIEF

 

Novel quantum phenomena in materials with strong Spin-Orbit coupling

The interplay between spin, orbital, and charge degrees of freedom are believed to govern novel quantum states of materials with strong relativistic spin-orbit coupling [REF]. We study the quantum properties of the Osmium-based double perovskite compounds as a function of the charge doping via cation partial substitution. The main aim is to investigate their magnetic ground states and to understand the key parameters which drive the system from the exotic canted-ferromagnetic to the canted-antiferromagnetic order.

In collaboration with Brown University (USA), Ohio State University (USA) and University of Wien (AU).

 

Spin manipulation at the Inorganic/molecular interface

The manipulation of electron spin and its associated magnetic moment is the key to build future electronic devices, which traditionally exploit just the electron charge in conventional inorganic materials such as metals and semiconductors. The very latest frontier of this field in the search for new materials is the study of heterostructures, such as molecules deposited on a ferromagnetic 3d metal which undergo extensive hybridization with the interface [REF1, REF2], yielding a highly spin-polarized molecular spinterface. The main aim of this project is to understand and control the key parameters which tune and modify the magnetic properties of thin ferromagnetic (FM), antiferromagnetic (AF) and paramagnetic (PM) films via their hybridization with selected molecular layers.

In collaboration with CNR-ISMN institute in Bologna, Italy.

 

Superconductivity

Superconductivity is a fascinating macroscopic quantum phenomenon which has attracted the interest of the scientific community for more than one century. Despite that and even though many technologies are now based on superconductors covering from medical diagnostic and research to energy and environmental purposes, the fundamental mechanism of superconductivity is still a mystery for many important classes of unconventional superconductors [REF].

In this project we aim to unveil the hidden parameters controlling the microscopic mechanism of superconductivity, i.e. controlling the strength of Cooper pairing, in different superconducting families.

In collaboration with many national (mainly Parma and Pavia Universities and SPIN-CNR) and international partners.

 

Magnetic interactions in pyrochlores

Spin degrees of freedom at the vertices of a lattice of corner-sharing tetrahedra can retain their degeneracy at low temperatures in the presence of a remarkable range of different types of interactions. In pyrochlore systems with general chemical formula A2B2O7 both the A and B sites form an interpenetrating network of corner-sharing tetrahedra and can contain magnetic ions, resulting in some novel short-range ordered phases characteristic of geometrically frustrated magnets such as spin glasses, spin ices, spin liquids, and much new physics [REF]. Here we study Molybdenum pyrochlores A2Mo2O7 (A= rare earth) which display a transition from a spin-glass ground state to a long-range ferromagnetic phase as a function of steric and structural parameters. Our aim is to identify the lattice parameters controlling the sign of the nearest-neighbor magnetic interactions when the superexchange or double- exchange interactions are favoured.

In collaboration with the University of Milan.

 

Quantum criticality in heavy fermion compounds

Quantum critical points (QCP) can be investigated in those physical systems that present a second order phase transition at T = 0. The transition can be tuned via external pressure, chemical pressure (by chemical substitution) and by applied magnetic field. Among the possible systems, heavy-fermion (HF) compounds represent some of the best examples to display low-temperature quantum criticality [REF]. In general, the ground state of HF compounds is determined by the competition between the local screening of 4f magnetic moments (the Kondo effect) and the inter-site magnetic interactions (the RKKY interaction). Here we aim to unveil the nature of the quantum phase transition of the Yb-based intermetallic compounds whose electronic and magnetic properties are dominated by the interplay between the on-site Kondo and the inter-site RKKY magnetic interactions.

In collaboration with the CNR-SPIN institute and the University of Genoa, Italy.

 

Spin dynamics in magnetic nanoparticles

Over the last 30 years a high number of studies concerning the magnetic properties of superparamagnetic nanostructures have been extensively studied, an effort motivated by the interest in the fundamental physics of low dimensional magnetic systems and by the widespread impact on medical and technological applications [REF]. Due to finite size effects, such as the high surface-to-volume atomic ratio and the single domain behaviour, magnetic nanoparticles exhibit considerably different magnetic properties than those found in their corresponding bulk materials. Here we aim to study the spin dynamics of the uncompensated surface spins which is expected to be different with respect to the one of the core spins, but still not well understood since it is difficult to be detected by many experimental techniques.

In collaboration with the University of Milan.

 

Molecular magnetism in Lanthanide nanomagnets

Molecular Magnetism is a research field that deals with the design and the investigation of new kind of magnets based on molecular units. Lanthanide complexes play a crucial role thanks to their large magnetic momentum and anisotropy [REF]. These features provide these systems with Single Ion Magnet (SIM) behavior, i.e. slow relaxation of the magnetization at low temperature and quantum tunneling effects. This makes them particularly appealing for the perspective creation of molecular devices for quantum information processing. We study the correlation between the electronic structure of the lanthanide ions in the complexes and the spin dynamics.

In collaboration with the University of Milan and Pavia.

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