Research | Condensed Matter Theory

Quantum phenomena, topology, and transport in low-dimensional systems

Low-dimensional systems, in which spatial dimensions are small enough to restrict the quantum mechanical wavefunction of electrons or atoms, exhibit some of the most diverse and intriguing phenomena seen in condensed matter physics. There has been tremendous interest in low-dimensional quantum systems during the last twenty years, fueled by a constant stream of striking discoveries, the realization of new state-of-art

electronic nanodevices and the potential applications in quantum technologies. Our group has concentrated its theoretical activity on the paradigm of low-dimensional systems, where “nanostructures” (based on superconductors or novel materials) can be engineered at the atomic scale. In addition, we have devoted our studies to low-dimensional systems of interest for quantum simulations, such as ultracold atomic gases
loaded in anisotropic traps and optical lattices. Other low-dimensional materials that have received considerable interest, since their discovery less than a decade ago, and for which our research has contributed, are graphene and topological materials. The group's theoretical work also concerns the study of Josephson anomalous effects in peculiar superconducting systems involving, for instance, semiconductive nanowires or interfaces between complex insulating oxides. Many of the subjects covered by our group are central to the currently fashionable fields of mesoscopic and topological physics, spintronics, spin-orbitronics, atomtronics, and quantum simulation.

Members of the research group:

• prof. R. Citro, E-Mail: rocitro@unisa.it
• prof. F. Romeo, E-Mail: fromeo@unisa.it
• Dr. Claudio Guarcello, E-Mail: cguarcello@unisa.it
• Dr. Alfonso Maiellaro, E-Mail: amaiellaro@unisa.it
• Mattia Trama, E-Mail: mtrama@unisa.it

External collaborators: Dr. Jacopo Settino (CNR)

International collaborations: Eugene Demler (ETH, Zurich), Thierry Giamarchi and Andrea Caviglia (University of Géneve), Edmond Orignac (ENS, Lyon), Corinna Kollath (University of Bonn)

Superconducting Orbitronics and Topological Superconductors

[Maria Teresa Mercaldo; email: mmercaldo@unisa.it]

(1) Orbitonics is a new type of electronics that aims to exploit the orbital degrees of freedom of electrons in solid-state devices. Indeed, the search for new electronic devices to achieve greater energy efficiency, miniaturization, and speed of operation, suggests to exploit the quantum degrees of freedom of electrons, such as spin and orbital angular momentum, rather than their charge. In this context, in our research group we study orbitronics effects in various physical systems and in particular in superconductors. The latter have the advantage of carrying current without dissipation. These studies pave the way for a new research field called superconducting orbitronics and in general have a great impact for the realization of superconducting electronic devices completely based on magneto-electric controls.

Collaborations within the Department: Carmine Ortix, Claudio Guarcello.

National collaborations: Mario Cuoco (CNR-SPIN, Salerno, Italy), Francesco Giazotto (CNR-NANO, Pisa, Italy), Luca Chirolli (CNR-Nano, Pisa).

(2) In recent years, in the scientific community, great interest has been directed to systems that present topological phases of matter. Devices based on unconventional or topological superconductors are fundamental elements for the development of new quantum technologies. In fact, topological ordered states have several properties that make them suitable both for the possibility of being used in quantum computing, since decoherence effects are significantly reduced, and in various electronic devices, exploiting their property of having states at the boundaries with zero energy (Majorana modes). In this context we study heterostructures and Josephsons junctions consisting of topological superconductors with Majorana states at the boundary in number greater than one. These studies are also motivated by the perspective of using such systems as constituent elements in devices for applications in the field of quantum computing.

National collaborations: Mario Cuoco (CNR-SPIN, Salerno, Italy)

International collaborations: Panagiotis Kotetes (CAS – ITP, Beijing, China), Yukio Tanaka (Nagoya University, Japan).