Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

AIP conference proceedings

Designing Interactions in Polar Molecules: Towards Novel Quantum Phases

Hans Peter Büchler, Guido Pupillo, Andrea Micheli, Mikhail D. Lukin, Eugene Demler, Nikolay V. Prokof'ev, P. Zoller

Published Jan 1, 2006• 0 citations
Publisher

Abstract

We study quantum degenerate polar molecules with large dipole moments. We show that the internal structure of the polar molecules allows us to tune and shape the long‐range part of the interaction, while the strength of the long‐range interaction easily exceeds the kinetic energy of the gas. The stability of the system is guaranteed by a strong transverse trapping potential confining the particles into two‐dimensional planes. For typical experimental parameters, we find the the ground state is characterized by a crystalline phase, separated from the superfluid phase via a quantum phase transition for a critical interaction strength.

DOI
10.1063/1.2400660

Related papers

Strongly Correlated 2D Quantum Phases with Cold Polar Molecules: Controlling the Shape of the Interaction Potential

Hans Peter Büchler, Eugene Demler, Mikhail D. Lukin +4 more

We discuss techniques to tune and shape the long-range part of the interaction potentials in quantum gases of bosonic polar molecules by dressing rotational excitations with static and microwave fields. This provides a novel tool towards engineering strongly correlated quantum phases in combination with low-dimensional trapping geometries. As an illustration, we discuss the 2D superfluid-crystal quantum phase transition for polar molecules interacting via an electric-field-induced dipole-dipole potential.

arXiv:cond-mat/0607294•Physical Review Letters•Feb 8, 2007•521 citations

Cold polar molecules in two-dimensional traps: Tailoring interactions with external fields for novel quantum phases

Andrea Micheli, Guido Pupillo, Hans Peter Büchler +1 more

We discuss techniques to engineer effective long-range interactions between polar molecules using external static electric and microwave fields. We consider a setup where molecules are trapped in a two-dimensional pancake geometry by a far-off-resonance optical trap, which ensures the stability of the dipolar collisions. We detail how to modify the shape and the strength of the long-range part of interaction potentials, which can be utilized to realize interesting quantum phases in the context of cold molecular gases.

arXiv:quant-ph/0703031•Physical Review A•Oct 3, 2007•221 citations

International Conference on Quantum Gases of Polar Molecules and Magnetic Atoms

S. Stringari, John L. Bohn, Eugene Demler +5 more

Recently ground state polar molecules have been successfully realized using stimulated Raman adiabatic passage (STIRAP) technique, which has stimulated new experimental activities along this direction in many laboratories. It is very promising that a stable and quantum degenerate gas of polar molecules can be realized in the near future. Such polar molecules have a large permanent electric dipole moment and hence strong long-range dipolar interaction effects in the presence of an electric field, giving rise to new few- and many-body phenomena that are absent in the traditional atomic systems explored so far.

•Jan 1, 2012•0 citations

Equilibrium and non-equilibrium phases of microwave-dressed polar molecules beyond rotational symmetries

Matteo Ciardi, Andreas Schindewolf, Tim Langen +1 more

Recent experiments on molecular droplets have opened a new frontier of self-organization in strongly dipolar quantum matter. Microwave-dressing of polar molecules permits to tune both the strength and the angular structure of long-range interactions, potentially promoting a rich spectrum of quantum phases, from superfluid droplets with varying geometry and insulating or supersolid droplet arrays to strongly correlated crystals of individual molecules. Using path-integral Monte Carlo simulations of large molecular ensembles, we demonstrate that experimentally observed droplet arrays emerge as a metastable non-equilibrium state from the quenching of a gas-droplet phase transition under entirely broken rotational symmetry of the microwave-induced interaction potential. We moreover find that a crystalline phase of molecules, predicted for antidipolar interactions, is absent under conditions of recent experiments. This is traced back to the lack of angular symmetry in currently employed microwave-dressing, which qualitatively reshapes the many-body energy landscape and cannot be captured by effective scalar interaction parameters. Our results provide the first direct comparison of ab initio simulations and experiments and establish interaction anisotropy as a key aspect of molecular quantum gases.

cond-mat.quant-gasCross-listedarXiv:2606.30589•Jun 30, 2026•0 citations

Mesoscopic dipolar quantum crystals

Massimo Boninsegni

The ground state of a two-dimensional, harmonically confined mesoscopic assembly of up to 30 polar molecules is studied by computer simulations. As the strength of the confining trap is increased, clusters evolve from superfluid, to supersolid, to insulating crystals. For strong confinement, the crystalline structure can be predicted based on classical energetics. However, clusters of specific numbers of particles (i.e., $N=12$ and $N=19$) display a nonclassical crystalline structure, stabilized by quantum effects, in an intermediate range of confinement strength. In these cases, coexistence of quantum and classical crystalline configurations is observed at finite temperature.

arXiv:1306.1266•Physical Review A•Jun 5, 2013•12 citations

Self-Bound Superfluid Membranes and Monolayer Crystals of Ultracold Polar Molecules

Matteo Ciardi, Kasper Rønning Pedersen, Tim Langen +1 more

We investigate the physics of ultracold dipolar molecules using path-integral quantum Monte Carlo simulations, and construct the complete phase diagram extending from weak to strong interactions and from small to mesoscopic particle numbers. Our calculations predict the formation of self-bound quantum droplets at interaction strengths lower than previous estimates for molecular condensates. Strikingly, we observe that, for stronger interactions, the oblate quantum droplet transitions to a two-dimensional sheet or superfluid membrane with a thickness of a single molecule. As interactions are increased further the system continually loses superfluidity while correlations develop, and is eventually found to undergo a transition to a crystalline monolayer that remains self-bound without external confinement. The spontaneous formation of such two-dimensional phases from a three-dimensional quantum gas is traced back to the peculiar anisotropic form of the dipole-dipole interaction generated by microwave dressing of rotational molecular states. For sufficiently large particle numbers, crystallization takes place for comparably low interaction strengths that do not promote two-body bound states and should thus be observable in ongoing experiments without limitations from three-body recombination.

arXiv:2504.02682•Physical Review Letters•Sep 15, 2025•10 citations
We study quantum degenerate polar molecules with large dipole moments. We show that the internal structure of the polar molecules allows us to tune and shape the long‐range part of the interaction, while the strength of the long‐range interaction easily exceeds the kinetic energy of the gas. The stability of the system is guaranteed by a strong transverse trapping potential confining the particles into two‐dimensional planes. For typical experimental parameters, we find the the ground state is characterized by a crystalline phase, separated from the superfluid phase via a quantum phase transition for a critical interaction strength.
We discuss techniques to tune and shape the long-range part of the interaction potentials in quantum gases of bosonic polar molecules by dressing rotational excitations with static and microwave fields. This provides a novel tool towards engineering strongly correlated quantum phases in combination with low-dimensional trapping geometries. As an illustration, we discuss the 2D superfluid-crystal quantum phase transition for polar molecules interacting via an electric-field-induced dipole-dipole potential.
We discuss techniques to engineer effective long-range interactions between polar molecules using external static electric and microwave fields. We consider a setup where molecules are trapped in a two-dimensional pancake geometry by a far-off-resonance optical trap, which ensures the stability of the dipolar collisions. We detail how to modify the shape and the strength of the long-range part of interaction potentials, which can be utilized to realize interesting quantum phases in the context of cold molecular gases.
Recently ground state polar molecules have been successfully realized using stimulated Raman adiabatic passage (STIRAP) technique, which has stimulated new experimental activities along this direction in many laboratories. It is very promising that a stable and quantum degenerate gas of polar molecules can be realized in the near future. Such polar molecules have a large permanent electric dipole moment and hence strong long-range dipolar interaction effects in the presence of an electric field, giving rise to new few- and many-body phenomena that are absent in the traditional atomic systems explored so far.
Recent experiments on molecular droplets have opened a new frontier of self-organization in strongly dipolar quantum matter. Microwave-dressing of polar molecules permits to tune both the strength and the angular structure of long-range interactions, potentially promoting a rich spectrum of quantum phases, from superfluid droplets with varying geometry and insulating or supersolid droplet arrays to strongly correlated crystals of individual molecules. Using path-integral Monte Carlo simulations of large molecular ensembles, we demonstrate that experimentally observed droplet arrays emerge as a metastable non-equilibrium state from the quenching of a gas-droplet phase transition under entirely broken rotational symmetry of the microwave-induced interaction potential. We moreover find that a crystalline phase of molecules, predicted for antidipolar interactions, is absent under conditions of recent experiments. This is traced back to the lack of angular symmetry in currently employed microwave-dressing, which qualitatively reshapes the many-body energy landscape and cannot be captured by effective scalar interaction parameters. Our results provide the first direct comparison of ab initio simulations and experiments and establish interaction anisotropy as a key aspect of molecular quantum gases.
The ground state of a two-dimensional, harmonically confined mesoscopic assembly of up to 30 polar molecules is studied by computer simulations. As the strength of the confining trap is increased, clusters evolve from superfluid, to supersolid, to insulating crystals. For strong confinement, the crystalline structure can be predicted based on classical energetics. However, clusters of specific numbers of particles (i.e., N=12N=12N=12 and N=19N=19N=19) display a nonclassical crystalline structure, stabilized by quantum effects, in an intermediate range of confinement strength. In these cases, coexistence of quantum and classical crystalline configurations is observed at finite temperature.
We investigate the physics of ultracold dipolar molecules using path-integral quantum Monte Carlo simulations, and construct the complete phase diagram extending from weak to strong interactions and from small to mesoscopic particle numbers. Our calculations predict the formation of self-bound quantum droplets at interaction strengths lower than previous estimates for molecular condensates. Strikingly, we observe that, for stronger interactions, the oblate quantum droplet transitions to a two-dimensional sheet or superfluid membrane with a thickness of a single molecule. As interactions are increased further the system continually loses superfluidity while correlations develop, and is eventually found to undergo a transition to a crystalline monolayer that remains self-bound without external confinement. The spontaneous formation of such two-dimensional phases from a three-dimensional quantum gas is traced back to the peculiar anisotropic form of the dipole-dipole interaction generated by microwave dressing of rotational molecular states. For sufficiently large particle numbers, crystallization takes place for comparably low interaction strengths that do not promote two-body bound states and should thus be observable in ongoing experiments without limitations from three-body recombination.