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Mercredi 25 septembre 2019

Mini-workshop !

par Revaz Ramazashvili - 25 septembre 2019

09:00 - 10:00 Matthieu Mambrini, Optimizing Monte Carlo sign problem.

10:00 - 11:00 Andreas Läuchli, Quantum Critical Phenomena and Tensor Networks :

In this talk I will review our recent work on the finite-correlation-length-scaling interpretation of the iPEPS tensor network method for quantum critical systems and will also sketch a new approach providing more accurate CFT data for one-dimensional systems based on iMPS tensor networks calculations.

11:00 - 12:00 Philippe Corboz, Simulations of the 2D Hubbard model with iPEPS :

An infinite projected entangled pair state (iPEPS) is a variational tensor network ansatz to represent 2D ground states in the thermodynamic limit where the accuracy can be systematically controlled by the bond dimension D of the tensors. Thanks to several methodological advances in recent years, iPEPS has become a very powerful tool for the study of 2D strongly correlated systems, in particular models where quantum Monte Carlo fails due to the negative sign problem.,In the first part of my talk I will report on recent progress in simulating the 2D Hubbard model with iPEPS, focussing on a particularly challenging point in the phase diagram, U/t=8 and 1/8 doping. A very close competition between several low-energy states is found, including a uniform d-wave superconducting state and different types of stripe states. Systematic extrapolations to the exact, infinite D limit show that the ground state is a period 8 stripe, while stripes with periods 5-7 being very close in energy. Consistent results are also obtained with density matrix embedding theory, density matrix renormalization group, and constrained-path auxiliary field quantum Monte Carlo. On the other hand, period 4 stripes - which are typically observed in experiments on the cuprates - are clearly higher in energy. However, I wlil show that they become energetically favored upon adding a realistic next-nearest neighbor hopping term to the model. In the second part I will also highlight recent progress in studying SU(N) Hubbard models at integer filling, and simulations at finite temperature with iPEPS.

13:30 - 14:30 Nicolas Laflorencie, Topics on MBL : multifractality - fragmentation - parent Hamiltonians.

14:30 - 15:30 Hugo Théveniaut, Two applications of machine learning in condensed matter physics.

15:30 - 16:30 Norbert Schuch, Order parameters for topological phases from tensor networks.

Post-scriptum :

contact : D. Poilblanc