The Condensed Matter Theory group at Sapienza University focuses on a wide range of topics in solid-state physics using both advanced field-theory analytical approaches and computational techniques. We investigate emerging new materials where several (electronic, lattice and magnetic) degrees of freedom compete and cooperate to generate phenomena not seen in conventional settings. The topics covered by the group range from superconductivity (both conventional and unconventional), quantum-critical phenomena, thermal transport, graphene-based materials, and magnetism in complex oxides. The group has a strong vocation for direct interaction with experimental colleagues, with several joint activities and a particular focus on understanding spectroscopic techniques (optical spectroscopies, electron energy-loss spectroscopy, inelastic X-ray diffraction, etc.).
High temperature superconductivity at high pressure
The discovery in 2015 of record-breaking superconductivity in H₃S above 200 K, followed in 2018 by the synthesis of LaH₁₀, a superconductor at 250 K, approaching room temperature, ignited tremendous interest in high-pressure superconductivity. Pressure fundamentally alters the chemistry of hydrogen, enabling this element to form metallic bonds through which electrons move without resistance. This research field is covered by multiple complementary approaches in our department. The group pioneered the development of a theory capable of capturing superconductivity in quantum materials where the quantum anharmonic motion of light hydrogen nuclei, and its dramatic effects on phonon lineshapes, hinders conventional approaches. Their work has been instrumental in explaining how anharmonicity reshapes the spectroscopic signatures of these hydrides, directly affecting predicted critical temperatures. We are world leaders in first-principles crystal-structure prediction of novel hydrides, exploiting chemical precompression that can stabilize high-temperature superconductivity at progressively lower, and ultimately ambient, pressures.
Quantum Fluctuations and Competing Orders in Cuprates
The group of Sergio Caprara and Marco Grilli investigates the intertwined behavior of electrons in high-temperature superconducting cuprates, seeking to explain why these materials behave so differently from ordinary metals. In the normal state above the superconducting transition, cuprates famously exhibit a "strange metal" phase where electrical resistance grows linearly with temperature—a puzzle that has persisted for decades. The group has proposed the "Shrinking Fermi Liquid" scenario, a theoretical picture in which slow, spatially localized fluctuations of electric charge act as a glue that scatters electrons in an unusual way, naturally producing this strange metallic behavior. The predicted charge fluctuations and their distinct spectroscopic fingerprints have been confirmed by resonant X-ray scattering experiments, validating the theory. The same charge fluctuations, when they freeze into a static pattern, create charge density waves that directly compete with superconductivity. Using simplified yet powerful models, the group has explored this competition, explaining striking experimental signatures like the "double-step" transition in transport measurements and providing a quantitative map of how superconductivity and charge order vie for control over the material's phase diagram. This unified approach links the mysteriously incoherent normal state to the coherent, zero-resistance superconducting state in a single, consistent framework.
Phase-Change Materials for Next-Generation Memory and Neuromorphic Computing
The most impactful recent research of the group of Riccardo Mazzarello focuses on the computational design and fundamental understanding of chalcogenide phase-change materials (PCMs)—the active materials at the heart of emerging non-volatile memory and brain-inspired computing technologies. These materials switch rapidly and reversibly between crystalline and amorphous states, a property that is now being exploited in commercial and prototype memory devices. The group's work addresses the key challenge of optimizing this switching: achieving simultaneously fast crystallization, high amorphous stability, and a large electrical contrast between the two phases. Using advanced ab initio simulations and machine-learned interatomic potentials, the group has unveiled how subtle features—such as the fragility of the supercooled liquid phase and the precise mass density of the amorphous state—govern crystallization kinetics and device performance at the atomic scale. By establishing these microscopic design rules, the group has not only clarified the physical origins of switching behavior in established materials like GeSbTe alloys, but also predicted entirely new families of layered PCMs—including recently identified magnetic candidates—that could integrate memory and logic functionalities in a single material. This research is therefore critical for pushing PCM technology beyond current limitations in speed, scalability, and energy efficiency, directly enabling the development of universal memory and neuromorphic hardware that mimic the brain's computational principles.
Hybrid Superconductor-Semiconductor Devices for Quantum Technologies
The group of Bernard van Heck works in the field of hybrid quantum devices, where superconductors are interfaced with semiconductors to engineer electronic states with no natural counterpart. The group’s contributions are focused on two intrinsically protected platforms for quantum information: Andreev spin qubits, where quantum information is encoded in spin states shielded by time-reversal symmetry, and topological superconductivity in full-shell nanowires, a route toward Majorana zero modes whose exotic braiding statistics could enable fault-tolerant quantum computation. The unifying theme is the theoretical design of hybrid interfaces where intrinsic protection and electrical controllability coexist, providing a blueprint for the next generation of quantum processors.
Nonlinear Terahertz Spectroscopy and Emergent Dynamics in Superconductors
The group of Lara Benfatto works at the frontier of nonequilibrium many-body physics, where intense terahertz light pulses are used to drive, probe, and understand the collective excitations of quantum materials far from equilibrium. A central line of activity concerns the nonlinear optical response of superconducting collective modes—particularly the Higgs and Josephson plasma oscillations—and the development of the theoretical framework underpinning advanced terahertz spectroscopies such as two-dimensional coherent spectroscopy. A second, closely related focus addresses the ultrafast dynamics of quantum paraelectrics like SrTiO₃, where nuclear quantum fluctuations suppress ferroelectric order. Here, a decisive methodological contribution has come from the time-dependent self-consistent harmonic approximation, developed by the group of Lorenzo Monacelli, which provides the first ab initio framework capable of simulating the nonequilibrium quantum nuclear dynamics of realistic materials under THz excitation. This synergy between theory and first-principles simulation has revealed how THz pump pulses generate persistent out-of-equilibrium stress that can transiently induce polar order, clarified the microscopic origin of phonon upconversion, and established a predictive blueprint for light-controlled quantum functionalities.
The group is currently composed of seven professors and one RTDB:
Lara Benfatto is Full Professor at the Physics Department. She holds a Ph.D. in Physics, and she has been a staff researcher at the Institute of Complex Systems of CNR until 2019, prior to her appointment as university professor. Her activity focuses mainly on theoretical aspects connected to the physics of correlated electron systems in low dimensions, including high-temperature cuprate and pnictide superconductors, graphene, dichalcogenides, disordered superconductors, and superconducting heterostructures. She is an expert of quantum field-theory approaches to many-body systems, with a specific interest in providing analytical solutions to describe realistic experimental settings. In recent years, she has focused particularly on developing a theoretical framework for understanding unconventional time-resolved THz spectroscopies, with applications ranging from superconducting collective modes to hybrid light-matter excitations and axial charge-density-wave materials.
Lilia Boeri is Full Professor at the Physics Department.
Sergio Caprara is Associate Professor at the Physics Department.
Marco Grilli is Full Professor at the Physics Department.
Francesco Mauri is Full Professor at the Physics Department.
Riccardo Mazzarello is Associate Professor at the Physics Department.
Lorenzo Monacelli is RTT at the Physics Department.
Bernard van Heck is Associate Professor at the Physics Department.