Now showing items 1-20 of 27

    • Berezinskii-Kosterlitz-Thouless transition in two-dimensional dipolar stripes 

      Bombín Escudero, Raul; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (American Physical Society (APS), 2019-12-05)
      Article
      Open Access
      A two-dimensional quantum system of dipoles, with a polarization angle not perpendicular to the plane, shows a transition from a gas to a stripe phase. We have studied the thermal properties of these two phases using the ...
    • Diffusion Monte Carlo methods for spin-orbit-coupled ultracold Bose gases 

      Sánchez Baena, Juan; Boronat Medico, Jordi; Mazzanti Castrillejo, Fernando Pablo (American Physical Society (APS), 2018-11-27)
      Article
      Open Access
      We present two diffusion Monte Carlo (DMC) algorithms for systems of ultracold quantum gases featuring synthetic spin-orbit interactions. The first one is a spin-integrated DMC method which provides fixed-phase energy ...
    • Dilute dipolar quantum droplets beyond the extended Gross-Pitaevskii equation 

      Bötcher, Fabian; Wenzel, Matthias; Schmidt, Jan-Niklas; Guo, Mingyang; Langen, Tim; Ferrier-Barbut, Igor; Pfau, Tilman; Bombín Escudero, Raul; Sánchez Baena, Juan; Boronat Medico, Jordi; Mazzanti Castrillejo, Fernando Pablo (American Physical Society, 2019-11-08)
      Article
      Open Access
      Dipolar quantum droplets are exotic quantum objects that are self-bound due to the subtle balance of attraction, repulsion, and quantum correlations. Here we present a systematic study of the critical atom number of these ...
    • Dipolar Bose Supersolid Stripes 

      Bombín Escudero, Raul; Boronat Medico, Jordi; Mazzanti Castrillejo, Fernando Pablo (2017-12-20)
      Article
      Open Access
      We study the superfluid properties of a system of fully polarized dipolar bosons moving in the XY plane. We focus on the general case where the polarization field forms an arbitrary angle a with respect to the Z axis, ...
    • Droplets of trapped quantum dipolar bosons 

      Macia Rey, Adrián; Sánchez Baena, Juan; Boronat Medico, Jordi; Mazzanti Castrillejo, Fernando Pablo (2016-11-10)
      Article
      Open Access
      Strongly interacting systems of dipolar bosons in three dimensions confined by harmonic traps are analyzed using the exact path integral ground-state Monte Carlo method. By adding a repulsive two-body potential, we find a ...
    • Ferromagnetic transition of a two-component Fermi gas of hard spheres 

      Arias de Saavedra, F.; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi; Polls, A. (2012-03-12)
      Article
      Open Access
      We use microscopic many-body theory to analyze the problem of itinerant ferromagnetism in a repulsive atomic Fermi gas of hard spheres. Using simple arguments we show that the available theoretical predictions for the onset ...
    • Few trapped quantum dipoles: quantum versus classical structures 

      Sánchez Baena, Juan; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (2018-01-31)
      Article
      Open Access
      We analyze the ground state of a two-dimensional quantum system of a few strongly confined dipolar bosons. Dipoles arrange in different stable structures that depend on the tilting polarization angle and the anisotropy of ...
    • Gapped spectrum in pair-superfluid bosons 

      Astrakharchik, Grigori; Zillich, Robert E.; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (2016-12-22)
      Article
      Open Access
      We study the ground state of a bilayer system of dipolar bosons with dipoles oriented by an external field perpendicularly to the two parallel planes. By decreasing the interlayer distance, for a fixed value of the strength ...
    • High-order time expansion path integral ground state 

      Rota, Riccardo; Casulleras Ambrós, Joaquín; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (2010-01)
      Article
      Open Access
      The feasibility of path integral Monte Carlo ground state calculations with very few beads using a high-order short-time Green’s function expansion is discussed. An explicit expression of the evolution operator which provides ...
    • Low-dimensional weakly interacting Bose gases: nonuniversal equations of state 

      Astrakharchik, Grigori; Boronat Medico, Jordi; Kurbakov, I L; Lozovik, Y E; Mazzanti Castrillejo, Fernando Pablo (2010-01)
      Article
      Open Access
      The zero-temperature equation of state is analyzed in low-dimensional bosonic systems. We propose to use the concept of energy-dependent s-wave scattering length for obtaining estimations of nonuniversal terms in the energy ...
    • Microscopic description of anisotropic low-density dipolar Bose gases in two dimensions 

      Macia Rey, Adrián; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi; Zillich, R.E. (2011-09-19)
      Article
      Open Access
      A microscopic description of the zero-energy two-body ground state and many-body static properties of anisotropic homogeneous gases of bosonic dipoles in two dimensions at low densities is presented and discussed. By ...
    • Neighborhood-based stopping criterion for contrastive divergence 

      Romero Merino, Enrique; Mazzanti Castrillejo, Fernando Pablo; Delgado Pin, Jordi (2018-07)
      Article
      Open Access
      Restricted Boltzmann Machines (RBMs) are general unsupervised learning devices to ascertain generative models of data distributions. RBMs are often trained using the Contrastive Divergence (CD) learning algorithm, an ...
    • One-dimensional Bose gas in optical lattices of arbitrary strength 

      Astrakharchik, Grigori; Krutitsky, K.V.; Lewenstein, Maciej; Mazzanti Castrillejo, Fernando Pablo (2016-02-08)
      Article
      Open Access
      One-dimensional Bose gas with contact interaction in optical lattices at zero temperature is investigated by means of the exact diffusion Monte Carlo algorithm. The results obtained from the fundamental continuous model ...
    • One-dimensional harmonically confined SU(N) fermions 

      Gordillo Bargueño, Maria Carmen; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (American Physical Society (APS), 2019-08-05)
      Article
      Open Access
      We study the momentum distributions and spatial correlations of few harmonically confined SU(N) fermions using quantum Monte Carlo methods. In our study, we vary the spin degeneracy N from 2 to 6 and the total number of ...
    • Optical lattices as a tool to study defect-induced superfluidity 

      Astrakharchik, Grigori; Krutitsky, K.V.; Lewenstein, Maciej; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (AMER PHYSICAL SOC, 2017-09-05)
      Article
      Open Access
      We study the superfluid response, the energetic and structural properties of a one-dimensional ultracold Bose gas in an optical lattice of arbitrary strength. We use the Bose-Fermi mapping in the limit of infinitely large ...
    • Phase diagram of dipolar bosons in two dimensions with tilted polarization 

      Macia Rey, Adrián; Boronat Medico, Jordi; Mazzanti Castrillejo, Fernando Pablo (2014-12-01)
      Article
      Open Access
      We analyze the ground state of a system of dipolar bosons moving in the XY plane and such that their dipolar moments are all aligned in a fixed direction in space. We focus on the general case where the polarization field ...
    • Pràctiques de Laboratori 

      Canales Gabriel, Manel; Trullàs Simó, Joaquim; Ametller Congost, Lluís; Llanta Salleras, Estanislao; Rey Oriol, Rosendo; Casulleras Ambrós, Joaquín; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi; Martí Rabassa, Jordi; Guàrdia Manuel, Elvira; Sesé Castel, Gemma; Pastor Satorras, Romualdo (Universitat Politècnica de Catalunya, 2015)
      Practice
      Open Access
    • Quantum Monte Carlo estimation of complex-time correlations for the study of the ground-state dynamic structure function 

      Rota, R; Casulleras Ambrós, Joaquín; Mazzanti Castrillejo, Fernando Pablo; Boronat Medico, Jordi (2015-03-21)
      Article
      Open Access
      We present a method based on the path integral Monte Carlo formalism for the calculation of ground-state time correlation functions in quantum systems. The key point of the method is the consideration of time as a complex ...
    • Self-bound Bose mixtures 

      Staudinger, Clemens; Mazzanti Castrillejo, Fernando Pablo; Zillich, Robert E. (American Physical Society (APS), 2018-08-31)
      Article
      Open Access
      Recent experiments confirmed that fluctuations beyond the mean-field approximation can lead to self-bound liquid droplets of ultradilute binary Bose mixtures. We proceed beyond the beyond-mean-field approximation and study ...
    • Single-particle versus pair superfluidity in a bilayer system of dipolar bosons 

      Macia Rey, Adrián; Astrakharchik, Grigori; Mazzanti Castrillejo, Fernando Pablo; Giorgini, Stefano; Boronat Medico, Jordi (2014-10-21)
      Article
      Open Access
      We consider the ground state of a bilayer system of dipolar bosons, where dipoles are oriented by an external field in the direction perpendicular to the parallel planes. Quantum Monte Carlo methods are used to calculate ...