Impurities and polarons in quantum neutral matter

Research on neutral impurities in quantum gases focuses on studying the behavior and effects of non-charged particles (neutral impurities) within ultra-cold atomic or molecular gases. These impurities are typically introduced into the quantum gas, and their interactions with the surrounding atoms or molecules are investigated. The study of neutral impurities in quantum gases has provided valuable insights into various physical phenomena, including quantum dynamics, quantum phase transitions, and many-body physics. This research is significant for understanding fundamental aspects of quantum systems and has potential applications in quantum computing, quantum simulation, and precision measurements.

Selected Publications
F. Grusdt, N. Mostaan, E. Demler and LAPA. REVIEW. Impurities and polarons in bosonic quantum gases: a review on recent progress (2025).
J. Levinsen, LAPA et.al. PRL (Edit. Sug) 127, 033401 (2021)
LAPA. PRA 103, 033323 (2021).
LAPA, N. B. Jørgensen, et.al, PRA 99. 063607 (2019).
A. Camacho-Guardian, LAPA, et.al, PRL. 121, 013401 (2018)
LAPA and S. Giorgini. PRA 92. 033612 (2015).

Impurities and polarons

Exotic states of the matter

Quantum droplets and superfluid solids, also known as supersolids, are fascinating phenomena observed in ultracold quantum gases. Quantum droplets are stable, self-bound entities formed by interactions between particles in a gas. Unlike traditional droplets, which are held together by surface tension, quantum droplets arise due to quantum fluctuations and repulsive interparticle interactions. These droplets exhibit unique properties such as density profiles that are spatially localized, effectively behaving as a macroscopic quantum object. On the other hand, supersolids are intriguing states of matter that combine characteristics of both solids and superfluids. In supersolids, atoms arrange in a crystal-like lattice while simultaneously flowing as a superfluid. These exotic states emerge when the repulsive interactions between atoms are balanced with quantum fluctuations, resulting in simultaneous long-range order and coherence. The study of quantum droplets and supersolids in ultracold quantum gases offers valuable insights into the fundamental nature of matter and opens up possibilities for exploring novel quantum phenomena and potential applications in quantum technologies.

Selected Publications
T. Bland, E. Poli, LAPA, et.al., PRA 106 053322 (2022)
D. Edler, LAPA, et.al. PRR 4, 033017 (2022)
R. Bisset, LAPA, and L. Santos. PRL 126, 025301 (2021)
D. Scheiermann, LAPA, et.al.. arXiv:2202.08259 (2022)

Exotic states of the matter

Atom-ion quantum hybrid systems

Atom-ion systems in ultracold gases provide a unique platform for studying a wide range of intriguing phenomena in quantum physics. One fascinating aspect is the formation of ion Bose polaron and ion Fermi polaron complexes. In an ion Bose polaron, an impurity ion interacts with a surrounding gas of bosonic atoms. The strong attractive interaction between the ion and the bosons leads to the dressing of the ion by the bosonic cloud, effectively forming a quasiparticle. This dressing modifies the properties of the ion, such as its mass and spectral features, creating a novel hybrid state. Similarly, in an ion Fermi polaron, the impurity ion interacts with a gas of fermionic atoms. Due to the Pauli exclusion principle, the dressing effect is different compared to the Bose polaron case, resulting in distinct behaviors and characteristics. These atom-ion systems with ultracold gases offer rich opportunities for studying the physics of polaron formation, many-body interactions, and quantum impurity effects, contributing to our understanding of strongly correlated systems and opening up avenues for potential applications in quantum simulation and information processing.

Selected Publications
LAPA. Nat Rev Phys, 4, 214 (2022).
G.E. Astrakharchik and LAPA, et.al, arXiv:2206.03476v1(2022)
R. Pessoa, S. A. Vitiello, and LAPA Phys. Rev. Lett. 133, 233002 – 2024.
G. E. A and LAPA, et.al. Comm Phys. (Nature) 4, 94 (2021)

Atom-ion quantum hybrid systems

Quantum Many body Physics in Condensed Matter

Quantum phenomena occurring in solid-state systems involve the collective effects of electrons, excitons, and other quasi-particles within condensed matter. Solid-state systems offer a flexible platform for investigating quantum phenomena including coherence, entanglement, and many body interactions in well-defined conditions. For example, such systems as exciton-polaritons, superconducting circuits, and stacked structures allow researchers to study dynamics and quantum phases out of equilibrium. It is the strong interaction effects, lower dimensionality, and controllability that make solid-state platforms an excellent choice to study quantum physics fundamentals and develop quantum technologies.

Selected Publications
S. Conti, A. Chaves, LAPA, et.al. PRB 112, 184514 (2025).
G. A. Domínguez-Castro, L. Santos, LAPA, et.al. PRB 113, 035111 (2026) (Editors' Suggestion).

Solid state platforms

Other interests

Computational methods for many body physics

We have expertise in quantum Monte Carlo methods (Variational, diffusion, Fixed node and path integral Monte Carlo) and the Gross–Pitaevskii equation, with a focus on many-body quantum systems and ultracold gases. My current goal is to bridge these approaches with modern techniques such as tensor networks and neural quantum states, in order to develop more powerful and scalable methods for simulating complex quantum systems.

Many-Body quantum optics

We aim to explore and develop theoretical approaches to study strongly interacting light–matter systems. In particular, I am interested in platforms such as exciton–polaritons, where quantum optical effects and many-body correlations interplay to give rise to novel collective phenomena. I intend to study these systems using and extending methods from quantum many-body theory to better understand their non-equilibrium dynamics, correlations, and emergent phases.

Dipolar quantum matter and long-ranged interactions

Bosonic atoms or molecules with strong, long-range dipole–dipole interactions provide a rich platform for studying novel quantum phases, driven by the interplay between interaction anisotropy, quantum statistics, and many-body effects. We are interested in understanding how dipolar interactions give rise to exotic states of matter, by applying many-body techniques (theory and numerics) to explore their equilibrium and dynamical properties.

Non equilibrium physics and open quantum systems

Another area I am interested in is that of open many-body quantum systems, in which the environment interaction is an important aspect. Unlike closed systems, open systems have a lot of nonequilibrium features like dissipation and decoherence. We will be investigating the development of many-body correlations and quantum coherence in open quantum systems.