Jacek Dziarmaga

Symmetry Breaking with a Slant: Topological Defects after an Inhomogeneous Quench

We show that, in second-order phase transformations induced by an inhomogeneous quench, the density of topological defects is drastically suppressed as the velocity with which the quench propagates becomes smaller than the speed at which the front of the broken symmetry phase spreads. The velocity of the broken symmetry phase front is approximately given by the ratio of the healing length to relaxation time at freeze-out, that is at the instant when the critical slowing down results in a transition from the adiabatic to the impulse behavior in the order parameter. Experimental implications are briefly discussed.

Double Universality of a Quantum Phase Transition in Spinor Condensates: Modification of the Kibble-Żurek Mechanism by a Conservation Law

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-Żurek mechanism. We explain the occurrence of two scaling laws by a model including postselection of spin domains due to the conservation of condensate magnetization.

Space and time renormalization in phase transition dynamics

When a system is driven across a quantum critical point at a constant rate, its evolution must become nonadiabatic as the relaxation time

Noncollinear magnetic order stabilized by entangled spin-orbital fluctuations.

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Topological Order in an Entangled SU(2)⊗XY Spin-Orbital Ring

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

Spontaneous symmetry breaking in a generalized orbital compass model

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Quench in the 1D Bose-Hubbard model: Topological defects and excitations from the Kosterlitz-Thouless phase transition dynamics

set at the time

Exotic spin orders driven by orbital fluctuations in the Kugel-Khomskii model

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Variational tensor network renormalization in imaginary time: Benchmark results in the Hubbard model at finite temperature

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.

Projected entangled pair states at finite temperature: Imaginary time evolution with ancillas

Quantum phase transitions in the two-dimensional Kugel-Khomskii model on a square lattice are studied using the plaquette mean field theory and the entanglement renormalization Ansatz. When 3z(2)-r(2) orbitals are favored by the crystal field and Hunds exchange is finite, both methods give a noncollinear exotic magnetic order that consists of four sublattices with mutually orthogonal nearest-neighbor and antiferromagnetic second-neighbor spins. We derive an effective frustrated spin model with second- and third-neighbor spin interactions which stabilize this phase and follow from spin-orbital quantum fluctuations involving spin singlets entangled with orbital excitations.