A5103701895- Quantum many-body systems
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Quantum, superfluid, helium dynamics
- Quantum and electron transport phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Topological Materials and Phenomena
- Theoretical and Computational Physics
University of Cologne
2024
Institute of Physics
2010-2016
We have discussed the tensor-network representation of classical statistical or interacting quantum lattice models, and given a comprehensive introduction to numerical methods we recently proposed for studying states/models in two dimensions. A second renormalization scheme is introduced take into account environment contribution calculation partition function models expectation values states. It improves significantly accuracy coarse-grained tensor renormalization-group method. In study...
The sign problem is a major obstacle in quantum Monte Carlo simulations for many-body fermion systems. We examine this with new perspective based on the Majorana reflection positivity and Kramers positivity. Two sufficient conditions are proven absence of problem. Our proof provides unified description all interacting lattice models previously known to be free auxiliary field method. It also allows us identify number sign-problem-free including, but not limited to, repulsive interactions...
We have precisely determined the ground state phase diagram of quantum spin-1 bilinear-biquadratic Heisenberg model on honeycomb lattice using tensor renormalization group method. find that ferromagnetic, ferroquadrupolar, and a large part antiferromagnetic phases are stable against fluctuations. However, around where is antiferroquadrupolar ordered in classical limit, fluctuations suppress completely all magnetic orders, leading to plaquette order which breaks symmetry but preserves spin...
We evaluate the thermodynamic properties of 4-state antiferromagnetic Potts model on Union-Jack lattice using tensor-based numerical methods. present strong evidence for a previously unknown, "entropy-driven," finite-temperature phase transition to partially ordered state. From thermodynamics models diced and centered lattices, we propose that transitions states are ubiquitous irregular lattices.
We propose a framework based on the concept of semigroup to understand fermion sign problem. By using properties contraction semigroups, we obtain sufficient conditions for quantum lattice models be sign-problem-free. Many previous results can considered as special cases our new results. As direct application results, construct class sign-problem-free models, which cannot understood by frameworks. This also provides an interesting aspect in understanding related many-body systems. establish...