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Swislocki T.,Instytut Fizyki PAN | Witkowska E.,Instytut Fizyki PAN | Dziarmaga J.,Instytut Fizyki Uniwersytetu Jagiellonskiego | Matuszewski M.,Instytut Fizyki PAN
Physical Review Letters | Year: 2013

We consider a phase transition from an antiferromagnetic to a phase separated ground state in a spin-1 Bose-Einstein condensate of ultracold atoms. We demonstrate the occurrence of two scaling laws, for the number of spin domain seeds just after the phase transition, and for the number of spin domains in the final, stable configuration. Only the first scaling can be explained by the standard Kibble-Zurek mechanism. We explain the occurrence of two scaling laws by a model including postselection of spin domains due to the conservation of condensate magnetization. © 2013 American Physical Society.


Witkowska E.,Instytut Fizyki PAN | Dziarmaga J.,Instytut Fizyki Uniwersytetu Jagiellonskiego | Swislocki T.,Instytut Fizyki PAN | Matuszewski M.,Instytut Fizyki PAN
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We investigate the dynamics and outcome of a quantum phase transition from an antiferromagnetic to a phase-separated ground state in a spin-1 Bose-Einstein condensate of ultracold atoms. We explicitly demonstrate double universality in the dynamics within experiments with various quench times. Furthermore, we show that spin domains created in the nonequilibrium transition constitute a set of mutually incoherent quasicondensates. The quasicondensates appear to be positioned in a semiregular fashion, which is a result of the conservation of local magnetization during the postselection dynamics. © 2013 American Physical Society.


Francuz A.,Instytut Fizyki Uniwersytetu Jagiellonskiego | Francuz A.,Los Alamos National Laboratory | Dziarmaga J.,Instytut Fizyki Uniwersytetu Jagiellonskiego | Gardas B.,Los Alamos National Laboratory | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

When a system is driven across a quantum critical point at a constant rate, its evolution must become nonadiabatic as the relaxation time τ diverges at the critical point. According to the Kibble-Zurek mechanism (KZM), the emerging post-transition excited state is characterized by a finite correlation length ξ set at the time t=τ when the critical slowing down makes it impossible for the system to relax to the equilibrium defined by changing parameters. This observation naturally suggests a dynamical scaling similar to renormalization familiar from the equilibrium critical phenomena. We provide evidence for such KZM-inspired spatiotemporal scaling by investigating an exact solution of the transverse field quantum Ising chain in the thermodynamic limit. © 2016 American Physical Society.


Czarnik P.,Instytut Fizyki Uniwersytetu Jagiellonskiego | Dziarmaga J.,Instytut Fizyki Uniwersytetu Jagiellonskiego
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We introduce a spin-orbital entangled (SOE) resonating valence bond (RVB) state on a square lattice of spins 12 and orbitals represented by pseudospins 12. Like the standard RVB state, it is a superposition of nearest-neighbor hard-core coverings of the lattice by spin singlets, but adjacent singlets are favored to have perpendicular orientations and, more importantly, an orientation of each singlet is entangled with orbitals state on its two lattice sites. The SOE-RVB state can be represented by a projected entangled pair state (PEPS) with a bond dimension D=4. This representation helps to reveal that the state is a superposition of striped coverings conserving a topological quantum number. The stripes are a critical quantum spin liquid. We propose a spin-orbital Hamiltonian supporting a SOE-RVB ground state. © 2015 American Physical Society.


Czarnik P.,Instytut Fizyki Uniwersytetu Jagiellonskiego | Dziarmaga J.,Instytut Fizyki Uniwersytetu Jagiellonskiego
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

The projected entangled pair state (PEPS) ansatz can represent a thermal state in a strongly correlated system. We introduce a variational algorithm to optimize this tensor network whose essential ingredient is an auxiliary tree tensor network (TTN). Since the full tensor environment is taken into account, with increasing bond dimension the PEPS-TTN ansatz provides the exact Gibbs state. Our presentation opens with a 1D version for a matrix product state (MPS-TTN) and then generalizes to PEPS-TTN in 2D. Benchmark results in the quantum Ising model are presented. © 2015 American Physical Society.

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