TY  - JOUR
AU  - Gligorić, Goran
AU  - Maluckov, Aleksandra
AU  - Stepić, Milutin
AU  - Hadžievski, Ljupčo
AU  - Malomed, Boris A.
PY  - 2010
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4117
AB  - We investigate the effects of dipole-dipole (DD) interactions on immiscibility-miscibility transitions (IMTs) in two-component Bose-Einstein condensates (BECs) trapped in the harmonic-oscillator (HO) potential, with the components linearly coupled by a resonant electromagnetic field (accordingly, the components represent two different spin states of the same atom). The problem is studied by means of direct numerical simulations. Different mutual orientations of the dipolar moments in the two components are considered. It is shown that, in the binary BEC formed by dipoles with the same orientation and equal magnitudes, the IMT cannot be induced by the DD interaction alone, being possible only in the presence of the linear coupling between the components, while the miscibility threshold is affected by the DD interactions. However, in the binary condensate with the two dipolar components polarized in opposite directions, the IMT can be induced without any linear coupling. Further, we demonstrate that those miscible and immiscible localized states, formed in the presence of the DD interactions, which are unstable evolve into robust breathers, which tend to keep the original miscibility or immiscibility, respectively. An exception is the case of a very strong DD attraction, when narrow stationary modes are destroyed by the instability. The binary BEC composed of copolarized dipoles with different magnitudes are briefly considered as well.
T2  - Physical Review A
T1  - Transition to miscibility in linearly coupled binary dipolar Bose-Einstein condensates
VL  - 82
IS  - 3
DO  - 10.1103/PhysRevA.82.033624
ER  - 

@article{
author = "Gligorić, Goran and Maluckov, Aleksandra and Stepić, Milutin and Hadžievski, Ljupčo and Malomed, Boris A.",
year = "2010",
abstract = "We investigate the effects of dipole-dipole (DD) interactions on immiscibility-miscibility transitions (IMTs) in two-component Bose-Einstein condensates (BECs) trapped in the harmonic-oscillator (HO) potential, with the components linearly coupled by a resonant electromagnetic field (accordingly, the components represent two different spin states of the same atom). The problem is studied by means of direct numerical simulations. Different mutual orientations of the dipolar moments in the two components are considered. It is shown that, in the binary BEC formed by dipoles with the same orientation and equal magnitudes, the IMT cannot be induced by the DD interaction alone, being possible only in the presence of the linear coupling between the components, while the miscibility threshold is affected by the DD interactions. However, in the binary condensate with the two dipolar components polarized in opposite directions, the IMT can be induced without any linear coupling. Further, we demonstrate that those miscible and immiscible localized states, formed in the presence of the DD interactions, which are unstable evolve into robust breathers, which tend to keep the original miscibility or immiscibility, respectively. An exception is the case of a very strong DD attraction, when narrow stationary modes are destroyed by the instability. The binary BEC composed of copolarized dipoles with different magnitudes are briefly considered as well.",
journal = "Physical Review A",
title = "Transition to miscibility in linearly coupled binary dipolar Bose-Einstein condensates",
volume = "82",
number = "3",
doi = "10.1103/PhysRevA.82.033624"
}

Gligorić, G., Maluckov, A., Stepić, M., Hadžievski, L.,& Malomed, B. A.. (2010). Transition to miscibility in linearly coupled binary dipolar Bose-Einstein condensates. in Physical Review A, 82(3).
https://doi.org/10.1103/PhysRevA.82.033624

Gligorić G, Maluckov A, Stepić M, Hadžievski L, Malomed BA. Transition to miscibility in linearly coupled binary dipolar Bose-Einstein condensates. in Physical Review A. 2010;82(3).
doi:10.1103/PhysRevA.82.033624 .

Gligorić, Goran, Maluckov, Aleksandra, Stepić, Milutin, Hadžievski, Ljupčo, Malomed, Boris A., "Transition to miscibility in linearly coupled binary dipolar Bose-Einstein condensates" in Physical Review A, 82, no. 3 (2010),
https://doi.org/10.1103/PhysRevA.82.033624 . .

TY  - JOUR
AU  - Gligorić, Goran
AU  - Maluckov, Aleksandra
AU  - Stepić, Milutin
AU  - Hadžievski, Ljupčo
AU  - Malomed, Boris A.
PY  - 2010
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4006
AB  - We analyze the formation and dynamics of bright unstaggered solitons in the disk-shaped dipolar Bose-Einstein condensate, which features the interplay of contact (collisional) and long-range dipole-dipole (DD) interactions between atoms. The condensate is assumed to be trapped in a strong optical-lattice potential in the disks plane, hence it may be approximated by a two-dimensional (2D) discrete model, which includes the on-site nonlinearity and cubic long-range (DD) interactions between sites of the lattice. We consider two such models, which differ by the form of the on-site nonlinearity, represented by the usual cubic term, or more accurate nonpolynomial one, derived from the underlying three-dimensional Gross-Pitaevskii equation. Similar results are obtained for both models. The analysis is focused on the effects of the DD interaction on fundamental localized modes in the lattice (2D discrete solitons). The repulsive isotropic DD nonlinearity extends the existence and stability regions of the fundamental solitons. New families of on-site, inter-site, and hybrid solitons, built on top of a finite background, are found as a result of the interplay of the isotropic repulsive DD interaction and attractive contact nonlinearity. By themselves, these solutions are unstable, but they evolve into robust breathers which exist on an oscillating background. In the presence of the repulsive contact interactions, fundamental localized modes exist if the DD interaction (attractive isotropic or anisotropic) is strong enough. They are stable in narrow regions close to the anticontinuum limit, while unstable solitons evolve into breathers. In the latter case, the presence of the background is immaterial.
T2  - Physical Review A
T1  - Two-dimensional discrete solitons in dipolar Bose-Einstein condensates
VL  - 81
IS  - 1
DO  - 10.1103/PhysRevA.81.013633
ER  - 

@article{
author = "Gligorić, Goran and Maluckov, Aleksandra and Stepić, Milutin and Hadžievski, Ljupčo and Malomed, Boris A.",
year = "2010",
abstract = "We analyze the formation and dynamics of bright unstaggered solitons in the disk-shaped dipolar Bose-Einstein condensate, which features the interplay of contact (collisional) and long-range dipole-dipole (DD) interactions between atoms. The condensate is assumed to be trapped in a strong optical-lattice potential in the disks plane, hence it may be approximated by a two-dimensional (2D) discrete model, which includes the on-site nonlinearity and cubic long-range (DD) interactions between sites of the lattice. We consider two such models, which differ by the form of the on-site nonlinearity, represented by the usual cubic term, or more accurate nonpolynomial one, derived from the underlying three-dimensional Gross-Pitaevskii equation. Similar results are obtained for both models. The analysis is focused on the effects of the DD interaction on fundamental localized modes in the lattice (2D discrete solitons). The repulsive isotropic DD nonlinearity extends the existence and stability regions of the fundamental solitons. New families of on-site, inter-site, and hybrid solitons, built on top of a finite background, are found as a result of the interplay of the isotropic repulsive DD interaction and attractive contact nonlinearity. By themselves, these solutions are unstable, but they evolve into robust breathers which exist on an oscillating background. In the presence of the repulsive contact interactions, fundamental localized modes exist if the DD interaction (attractive isotropic or anisotropic) is strong enough. They are stable in narrow regions close to the anticontinuum limit, while unstable solitons evolve into breathers. In the latter case, the presence of the background is immaterial.",
journal = "Physical Review A",
title = "Two-dimensional discrete solitons in dipolar Bose-Einstein condensates",
volume = "81",
number = "1",
doi = "10.1103/PhysRevA.81.013633"
}

Gligorić, G., Maluckov, A., Stepić, M., Hadžievski, L.,& Malomed, B. A.. (2010). Two-dimensional discrete solitons in dipolar Bose-Einstein condensates. in Physical Review A, 81(1).
https://doi.org/10.1103/PhysRevA.81.013633

Gligorić G, Maluckov A, Stepić M, Hadžievski L, Malomed BA. Two-dimensional discrete solitons in dipolar Bose-Einstein condensates. in Physical Review A. 2010;81(1).
doi:10.1103/PhysRevA.81.013633 .

Gligorić, Goran, Maluckov, Aleksandra, Stepić, Milutin, Hadžievski, Ljupčo, Malomed, Boris A., "Two-dimensional discrete solitons in dipolar Bose-Einstein condensates" in Physical Review A, 81, no. 1 (2010),
https://doi.org/10.1103/PhysRevA.81.013633 . .

TY  - JOUR
AU  - Hadžievski, Ljupčo
AU  - Gligorić, Goran
AU  - Maluckov, Aleksandra
AU  - Malomed, Boris A.
PY  - 2010
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4099
AB  - Fundamental solitons pinned to the interface between two discrete lattices coupled at a single site are investigated. Serially and parallel-coupled identical chains (system 1 and system 2), with self-attractive on-site cubic nonlinearity, are considered in one dimension. In these two systems, which can be readily implemented as arrays of nonlinear optical waveguides, symmetric, antisymmetric, and asymmetric solitons are investigated by means of the variational approximation (VA) and numerical methods. The VA demonstrates that the antisymmetric solitons exist in the entire parameter space, while the symmetric and asymmetric modes can be found below some critical value of the coupling parameter. Numerical results confirm these predictions for the symmetric and asymmetric fundamental modes. The existence region of numerically found antisymmetric solitons is also limited by a certain value of the coupling parameter. The symmetric solitons are destabilized via a supercritical symmetry-breaking pitchfork bifurcation, which gives rise to stable asymmetric solitons, in both systems. The antisymmetric fundamental solitons, which may be stable or not, do not undergo any bifurcation. In bistability regions, stable antisymmetric solitons coexist with either symmetric or asymmetric solitons.
T2  - Physical Review A
T1  - Interface solitons in one-dimensional locally coupled lattice systems
VL  - 82
IS  - 3
DO  - 10.1103/PhysRevA.82.033806
ER  - 

@article{
author = "Hadžievski, Ljupčo and Gligorić, Goran and Maluckov, Aleksandra and Malomed, Boris A.",
year = "2010",
abstract = "Fundamental solitons pinned to the interface between two discrete lattices coupled at a single site are investigated. Serially and parallel-coupled identical chains (system 1 and system 2), with self-attractive on-site cubic nonlinearity, are considered in one dimension. In these two systems, which can be readily implemented as arrays of nonlinear optical waveguides, symmetric, antisymmetric, and asymmetric solitons are investigated by means of the variational approximation (VA) and numerical methods. The VA demonstrates that the antisymmetric solitons exist in the entire parameter space, while the symmetric and asymmetric modes can be found below some critical value of the coupling parameter. Numerical results confirm these predictions for the symmetric and asymmetric fundamental modes. The existence region of numerically found antisymmetric solitons is also limited by a certain value of the coupling parameter. The symmetric solitons are destabilized via a supercritical symmetry-breaking pitchfork bifurcation, which gives rise to stable asymmetric solitons, in both systems. The antisymmetric fundamental solitons, which may be stable or not, do not undergo any bifurcation. In bistability regions, stable antisymmetric solitons coexist with either symmetric or asymmetric solitons.",
journal = "Physical Review A",
title = "Interface solitons in one-dimensional locally coupled lattice systems",
volume = "82",
number = "3",
doi = "10.1103/PhysRevA.82.033806"
}

Hadžievski, L., Gligorić, G., Maluckov, A.,& Malomed, B. A.. (2010). Interface solitons in one-dimensional locally coupled lattice systems. in Physical Review A, 82(3).
https://doi.org/10.1103/PhysRevA.82.033806

Hadžievski L, Gligorić G, Maluckov A, Malomed BA. Interface solitons in one-dimensional locally coupled lattice systems. in Physical Review A. 2010;82(3).
doi:10.1103/PhysRevA.82.033806 .

Hadžievski, Ljupčo, Gligorić, Goran, Maluckov, Aleksandra, Malomed, Boris A., "Interface solitons in one-dimensional locally coupled lattice systems" in Physical Review A, 82, no. 3 (2010),
https://doi.org/10.1103/PhysRevA.82.033806 . .

TY  - JOUR
AU  - Gligorić, Goran
AU  - Maluckov, Aleksandra
AU  - Hadžievski, Ljupčo
AU  - Malomed, Boris A.
PY  - 2009
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/3742
AB  - A model of the Bose-Einstein condensate (BEC) of dipolar atoms, confined in a combination of a cigar-shaped trap and optical lattice acting in the axial direction, is studied in the framework of the one-dimensional (1D) nonpolynomial Schrodinger equation (NPSE) with additional terms describing long-range dipole-dipole (DD) interactions. The NPSE makes it possible to describe the collapse of localized modes, which was experimentally observed in the self-attractive BEC confined in tight traps, in the framework of the 1D description. We study the influence of the DD interactions on the dynamics of bright solitons, especially concerning their collapse-induced instability. Both attractive and repulsive contact and DD interactions are considered. The results are summarized in the form of stability/collapse diagrams in a respective parametric space. In particular, it is shown that the attractive DD interactions may prevent the collapse instability in the condensate with attractive contact interactions.
T2  - Journal of Physics. B: Atomic Molecular and Optical Physics
T1  - Collapse instability of solitons in the nonpolynomial Schrodinger equation with dipole-dipole interactions
VL  - 42
IS  - 14
DO  - 10.1088/0953-4075/42/14/145302
ER  - 

@article{
author = "Gligorić, Goran and Maluckov, Aleksandra and Hadžievski, Ljupčo and Malomed, Boris A.",
year = "2009",
abstract = "A model of the Bose-Einstein condensate (BEC) of dipolar atoms, confined in a combination of a cigar-shaped trap and optical lattice acting in the axial direction, is studied in the framework of the one-dimensional (1D) nonpolynomial Schrodinger equation (NPSE) with additional terms describing long-range dipole-dipole (DD) interactions. The NPSE makes it possible to describe the collapse of localized modes, which was experimentally observed in the self-attractive BEC confined in tight traps, in the framework of the 1D description. We study the influence of the DD interactions on the dynamics of bright solitons, especially concerning their collapse-induced instability. Both attractive and repulsive contact and DD interactions are considered. The results are summarized in the form of stability/collapse diagrams in a respective parametric space. In particular, it is shown that the attractive DD interactions may prevent the collapse instability in the condensate with attractive contact interactions.",
journal = "Journal of Physics. B: Atomic Molecular and Optical Physics",
title = "Collapse instability of solitons in the nonpolynomial Schrodinger equation with dipole-dipole interactions",
volume = "42",
number = "14",
doi = "10.1088/0953-4075/42/14/145302"
}

Gligorić, G., Maluckov, A., Hadžievski, L.,& Malomed, B. A.. (2009). Collapse instability of solitons in the nonpolynomial Schrodinger equation with dipole-dipole interactions. in Journal of Physics. B: Atomic Molecular and Optical Physics, 42(14).
https://doi.org/10.1088/0953-4075/42/14/145302

Gligorić G, Maluckov A, Hadžievski L, Malomed BA. Collapse instability of solitons in the nonpolynomial Schrodinger equation with dipole-dipole interactions. in Journal of Physics. B: Atomic Molecular and Optical Physics. 2009;42(14).
doi:10.1088/0953-4075/42/14/145302 .

Gligorić, Goran, Maluckov, Aleksandra, Hadžievski, Ljupčo, Malomed, Boris A., "Collapse instability of solitons in the nonpolynomial Schrodinger equation with dipole-dipole interactions" in Journal of Physics. B: Atomic Molecular and Optical Physics, 42, no. 14 (2009),
https://doi.org/10.1088/0953-4075/42/14/145302 . .