laboratoire de physique statistique
 
 
laboratoire de physique statistique

Publications

Rechercher
Kris VAN HOUCKE 


2
P U B L I C A T I O N S

S E L E C T I O N N E R
P A R M I :




 
2015
Diagrammatic Monte Carlo study of the acoustic and the Bose-Einstein condensate polaron - Vlietinck, Jonas and Casteels, Wim and Van Houcke, Kris and Tempere, Jacques and Ryckebusch, Jan and Devreese, Jozef T.
NEW JOURNAL OF PHYSICS 17 (2015) 
LPS


Abstract : We consider two large polaron systems that are described by a Frohlich type of Hamiltonian, namely the Bose-Einstein condensate (BEC) polaron in the continuum and the acoustic polaron in a solid. We present ground-state energies of these two systems calculated with the Diagrammatic Monte Carlo (DiagMC) method and with a Feynman all-coupling approach. The DiagMC method evaluates up to very high order a diagrammatic series for the polaron's self-energy. The Feynman all-coupling approach is a variational method that has been used for a wide range of polaronic problems. For the acoustic and BEC polaron both methods provide remarkably similar non-renormalized ground-state energies that are obtained after introducing a finite momentum cutoff. For the renormalized ground-state energies of the BEC polaron, there are relatively large discrepancies between the DiagMC and the Feynman predictions. These differences can be attributed to the renormalization procedure for the contact interaction.
 
2014
Diagrammatic Monte Carlo study of the Fermi polaron in two dimensions - Vlietinck, Jonas and Ryckebusch, Jan and Van Houcke, Kris
PHYSICAL REVIEW B 89 (2014) 
LPS


Abstract : We study the properties of the two-dimensional Fermi polaron model in which an impurity attractively interacts with a Fermi sea of particles in the zero-range limit. We use a diagrammatic Monte Carlo (DiagMC) method which allows us to sample a Feynman diagrammatic series to very high order. The convergence properties of the series and the role of multiple particle-hole excitations are discussed. We study the polaron and molecule energy as a function of the coupling strength, revealing a transition from a polaron to a molecule in the ground state. We find a value for the critical interaction strength which complies with the experimentally measured one and predictions from variational methods. For all considered interaction strengths, the polaron Z factor from the full diagrammatic series almost coincides with the one-particle-hole result. We also formally link the DiagMC and the variational approaches for the polaron problem at hand.