arXiv subjects

Soumyadeep Halder

Publications and source records attributed to Soumyadeep Halder.

10 recordsLinked to original sources

arXiv2026

Mass-anisotropy driven stripe pattern formation and directional modulational instability in polariton condensate

Motivated by recent experimental advances toward electrical control of the effective mass and the realization of anisotropic mass distributions, we investigate the impact of mass anisotropy on driven-dissipative polariton condensates, focusing on modulational instability, pattern formation, and the collective dynamics of the emergent patterns. We show that unequal effective masses along the two orthogonal directions induce stripe pattern formation in an exciton-polariton condensate pumped by a non-resonant Gaussian laser beam above a critical mass ratio. A Bogoliubov analysis of the homogeneously pumped system reveals that mass anisotropy leaves the modulational-instability criteria unchanged but reshapes the unstable-mode dispersion by reducing the most unstable wave- length along the direction of larger effective mass with increasing mass ratio. This introduces an anisotropy-controlled length scale for pattern selection. When the pump width becomes comparable to the most unstable wavelength, the condensate becomes modulationally unstable and develops stripe patterns along the direction of larger effective mass, accompanied by particle-number fluctua- tions and center-of-mass oscillations along the same direction. As the pump width increases further, the stripes become distorted and develop spatial irregularities during the time evolution, indicative of modulational instability. Nevertheless, the anisotropic mass distribution preserves a pronounced directional preference, in contrast to the fully disordered patterns observed in the isotropic-mass case. Our results identify mass anisotropy as a key control parameter for directional modulational instability and pattern formation in nonequilibrium polariton condensates.

cond-mat.quant-gas↗

arXiv2026

Response of a dipolar BEC to Laguerre-Gaussian beam driven STIRAP

Coherent light-matter coupling via STIRAP can offer a versatile route to nucleate quantized vortices in Bose-Einstein condensates through the orbital angular momentum transfer from a vortex beam, yet its efficacy in dipolar condensates remains an open question. Can the orbital angular momentum of a Laguerre-Gaussian beam be coherently transferred to a dipolar BEC via STIRAP? We investigate this for a quasi-two-dimensional trapped dipolar condensate using co-propagating Gaussian and Laguerre-Gaussian laser beams. The interplay between long-range dipole-dipole interactions and short-range contact interactions enables access to three interaction-driven phases: superfluid, droplet, and supersolid. We find that the amount of angular momentum transferred from the optical field to the dipolar condensate, along with the nucleation and persistence of vortices, depends strongly on the underlying phases of the dipolar BEC. In the superfluid, STIRAP achieves a near-complete population transfer and nucleates a long-lived quantized vortex, reflecting efficient transfer of angular momentum to the condensate. In the droplet phase, although the vortex remains pinned within the density profile, the angular momentum is partially retained and oscillatory, accompanied by droplet fragmentation and recombination. In the supersolid phase, when the external magnetic field is oriented perpendicular to the LG beam's propagation direction, the emergence of a modulated density distribution along with a slight reduction in inter-droplet coherence leads to vortex delocalization and eventually exits from the condensate along the field direction, yielding a vanishing average angular momentum. However, reorienting the magnetic polarization along the beam propagation direction restores efficient angular momentum transfer and stabilizes the vortex within the supersolid phase.

cond-mat.quant-gas↗

arXiv2025

Dynamical signatures of superfluidity and shear rigidity in different phases of a dipolar Bose-Einstein condensate

We show that a sudden change in the polarization direction of the magnetic dipole moments of the atoms in a dipolar Bose-Einstein condensate (BEC) can serve as a useful dynamical probe to sense its superfluid and solid-like properties. We find that for small angular deviation of the polarization direction, actuated for instance by modifying an external magnetic field, the superfluid state undergoes an undamped scissors mode oscillation, a characteristic signature of superfluidity. In contrast, both the droplet and supersolid states exhibit a scissors-mode oscillation, which is effectively damped due to multiple closely spaced frequency components. Notably, we find that this damping rate provides a qualitative measure for the rigidity of different phases of a dipolar BEC. Furthermore, there exists a maximum angular deviation of the polarization direction, beyond which the droplet and the supersolid states undergo a permanent deformation i.e., we find an analog of the usual elastic to plastic phase transition of solids. We characterize this transition numerically using the fidelity of the condensate wavefunction with the ground state as well as the droplet width and periodicity of the supersolid density of the condensate which are experimentally accessible. Thus, the dynamical protocol introduced here can be an important experimental benchmark to identify and characterize the superfluid and solid properties of different phases of dipolar BECs.

cond-mat.quant-gas↗

arXiv2024

Magnetization induced skyrmion dynamics of a spin-orbit-coupled spinor condensate under sinusoidally varying magnetic field

We theoretically explore the spin texture dynamics of a harmonically trapped spin-1 Bose-Einstein condensate with Rashba spin-orbit coupling and ferromagnetic spin-exchange interactions under a sinusoidally varying magnetic field along the $x$-direction. This interplay yields an intrinsic spin texture in the ground state, forming a linear chain of alternating skyrmions at the saddle points. Our study analyzes the spin-mixing dynamics for both a freely evolving and a controlled longitudinal magnetization. The spin-1 system exhibits the Einstein-de Hass effect for the first case, for which an exchange between the total orbital angular momentum and the spin angular momentum is observed, resulting in minimal oscillations about the initial position of the skyrmion chain. However, for the fixed magnetization dynamics, the skyrmion chain exhibits ample angular oscillations about the equilibrium position, with the temporary formation of new skyrmions and anti-skyrmions to facilitate the oscillatory motion. Keeping the magnetization constant, this contrast now stems from the exchange between the canonical and spin-dependent contribution to the orbital angular momentum. The variation in canonical angular momentum is linked to the angular oscillations, while the spin-dependent angular momentum accounts for the creation or annihilation of skyrmions. We confirm the presence of scissor mode excitations in the spin texture due to the angular skyrmion oscillations.

cond-mat.quant-gas↗

arXiv2024

Roadmap to vortex nucleation below critical rotation frequency in a dipolar Bose-Einstein condensate

The formation of quantized vortices in a superfluid above a certain critical trap rotation frequency serves as a hallmark signature of superfluidity. Based on the beyond mean field framework, crucial for the formation of exotic supersolid and droplet states, we investigate dynamic protocols for vortex nucleation in the superfluid and supersolid states of a dipolar Bose-Einstein condensate (BEC), at a significantly lower trap rotation frequency. We find that the critical rotation frequency of the trap varies with the dipole-dipole interaction strength and the polarization direction of the external magnetic field. Leveraging these characteristics of dipolar BECs, we demonstrate three dynamic protocols for vortex nucleation even when rotating below the critical rotation frequency viz.: (i) varying the $s$-wave scattering length, (ii) changing the polarizing angle, and (iii) successive modulation of both the scattering length and polarizing angle. These dynamic vortex seeding protocols could serve as important benchmarks for future experimental studies.

cond-mat.quant-gas↗

arXiv2024

Induced supersolidity and hypersonic flow of a dipolar Bose-Einstein Condensate in a rotating bubble trap

Motivated by the recent realization of space-borne Bose-Einstein Condensates (BECs) under micro-gravity conditions, we extend the understanding of ultracold dipolar bosonic gases by exploring their behavior in a novel trapping configuration known as the ``bubble trap" topology. Utilizing the three-dimensional numerical simulations within the extended Gross-Pitaevskii framework, we unveil diverse ground state phases in this static curved topology. Subsequently, we investigate the influence of rotation on a dipolar BEC confined to the surface of a spherical bubble. Our findings reveal that the rotation of a bubble trap at certain rotation frequencies can modify the effective local dipole-dipole interaction strength, leading to the induction of supersolidity and the formation of quantum droplets. In addition, we demonstrate that a bubble trap can sustain high circulation, with the flow persisting for a longer time. Significantly, adjusting the rf detuning parameter allows the condensate to achieve hypersonic velocity. Finally, we also explore the impact of drastic change in the topological nature of the trap on the rotating dipolar BEC, transitioning from a filled shell trap to a bubble trap and vice versa. Based on the results of the topological transition, we propose a dynamic protocol to drive the interacting atomic gas into the quantum Hall regime.

cond-mat.quant-gas↗

arXiv2024

Sinusoidal magnetic field induced topological excitations in a spin-orbit coupled spinor condensate

We explore topological excitations in a spin-1 Bose-Einstein condensate subjected to an in-plane sinusoidally varying magnetic field and Rashba spin-orbit coupling (SOC). In the absence of SOC, the periodic magnetic field induces vortex-anti-vortex structures in the $\ket{F=1, m_F=\pm1}$ condensates at saddle-points, such that the net topological charge remains zero. The introduction of Rashba SOC breaks the system's symmetry, leading to non-conservation of overall angular momentum in the spin-1 condensate. This anisotropy results in the emergence of certain skyrmion spin textures. We provide a comparative study for various in-plane magnetic field configurations while keeping the SOC strength constant. Our numerical simulations within the mean-field framework reveal the potential to engineer diverse topological excitations controlled by the interplay between spin-orbit coupling and in-plane magnetic field in a spinor condensate.

cond-mat.quant-gas↗

arXiv2023

Induced supersolidity in a Dy-Er mixture

Recent experimental realization of the heteronuclear dipolar mixture of Dy and Er atoms opens fascinating prospects for creating intriguing novel phases in dipolar quantum gases. The experimentally measured value of intra-species $s$-wave scattering length of $^{166}$Er condensate in a $^{164}$Dy-$^{166}$Er mixture is larger than its intra-species dipolar length, implies that the $^{166}$Er condensate itself will not be in a regime of dominated dipole-dipole interaction (DDI). However, we find that the presence of $^{164}$Dy atoms with high magnetic moment induces droplet nucleation and supersolidity in $^{166}$Er condensate via the long-range and anisotropic inter-species DDI. Remarkably, we find that the imbalance in the magnetic dipole moment combined with its strong anisotropic coupling led to the emergence of unique ground state phases. The emerging phases include doubly superfluid states, a mixture of insulating droplets and supersolid states, binary supersolids with uniform and alternating domains and a combination of supersolid-superfluid mixed states. We delineate the properties of all these ground state phases and construct a phase diagram. We also explore the dynamical evolution across these phase boundaries via a linear quench of inter-species scattering length. Although we have demonstrated the result for the $^{164}$Dy-$^{166}$Er mixture, our results are generally valid for other dipolar bosonic mixtures of different Dy-Er isotope combinations and may become an important benchmark for future experimental scenarios.

cond-mat.quant-gas↗

arXiv2023

Rayleigh-Taylor instability in a phase-separated three-component Bose-Einstein condensate

We investigate the Rayleigh-Taylor instability at the two interfaces in a phase-separated three-component Bose-Einstein condensate in the mean-field framework. The subsequent dynamics in the immiscible three-component condensate has been studied in detail for different cases of instigating the instability in the system. The rotational symmetry of the system breaks when the atom-atom interaction is tuned in such a way that the interface between the components becomes unstable giving rise to non-linear patterns of mushroom shapes which grow exponentially with time. We also identify these non-linear patterns as the solutions of the angular Mathieu equation, representing the normal modes.

cond-mat.quant-gas↗

arXiv2023

Two-dimensional miscible-immiscible supersolid and droplet crystal state in a homonuclear dipolar bosonic mixture

The recent realization of binary dipolar BEC [Phys. Rev. Lett. 121, 213601 (2018)] opens new exciting aspects for studying quantum droplets and supersolids in a binary mixture. Motivated by this experiment, we study groundstate phases and dynamics of a Dy-Dy mixture. Dipolar bosonic mixture exhibits qualitatively novel and rich physics. Relying on the three-dimensional numerical simulations in the extended Gross-Pitaevskii framework, we unravel the groundstate phase diagrams and characterize different groundstate phases. The emergent phases include both miscible and immiscible single droplet (SD), multiple droplets (MD), supersolid (SS), and superfluid (SF) states. More intriguing mixed groundstates may occur for an imbalanced binary mixture, including a combination of SS-SF, SS-MD, and SS-SS phases. We observed the dynamical transition from a miscible MD state to an immiscible MD state with multiple domains formed along the axial direction by tuning the inter-species scattering length. Also by linear quenches of intra-species scattering lengths across the aforementioned phases, we monitor the dynamical formation of supersolid clusters and droplet lattices. Although we have demonstrated the results for a Dy-Dy mixture and for a specific parameter range of intra-species and inter-species scattering lengths, our results are generally valid for other dipolar mixtures and may become an important benchmark for future experimental scenarios.

cond-mat.quant-gas↗