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19 pages, 546 KB

Open AccessArticle

Multichannel Quantum Defect Theory with Numerical Reference Functions: Applications to Cold Atomic Collisions

by Dibyendu Sardar, Arpita Rakshit, Somnath Naskar and Bimalendu Deb

Atoms 2026, 14(3), 26; https://doi.org/10.3390/atoms14030026 - 21 Mar 2026

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We develop a method for calculating multichannel wavefunctions in the spirit of quantum defect theory, based on numerically calculated reference functions. We benchmark the method by calculating cold collisional properties of ⁸⁵Rb and ⁶Li in the presence of external magnetic fields tuned across specific s-wave Feshbach resonances and thereby reproducing known results. We then apply the method to calculate experimentally observed d-wave Feshbach resonance in ⁸⁷Rb-⁸⁵Rb cold collisions. Our numerical results for this d-wave resonance show good agreement with the experimental observations. The method is applicable to arbitrary interaction potentials and to any energy range near the scattering threshold. The implementation of our method to any multichannel two-body scattering problem is straightforward. Full article

(This article belongs to the Section Quantum Chemistry, Computational Chemistry and Molecular Physics)

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12 pages, 2128 KB

Open AccessArticle

Pairing Superfluid–Insulator Transition Induced by Atom–Molecule Conversion in Bosonic Mixtures in Optical Lattice

by Haiming Deng, Zhi Tan, Chao Kong, Fuqiu Ye and Honghua Zhong

Symmetry 2023, 15(9), 1715; https://doi.org/10.3390/sym15091715 - 7 Sep 2023

Cited by 1 | Viewed by 2096

Abstract

Motivated by the recent experiment on bosonic mixtures of atoms and molecules, we investigate pairing superfluid–insulator (SI) transition for bosonic mixtures of atoms and molecules in a one-dimensional optical lattice, which is described by an extended Bose–Hubbard model with atom–molecule conservation (AMC). It is found that AMC can induce an extra pair–superfluid phase though the system does not demonstrate pair-hopping. In particular, the system may undergo several pairing SI or insulator–superfluid transitions as the detuning from the Feshbach resonance is varied from negative to positive, and the larger positive detuning can bifurcate the pair–superfluid phases into mixed superfluid phases consisting of single-atomic and pair-atomic superfluid. The calculation of the second-order Rényi entropy reveals that the discontinuity in its first-order derivative corresponds to the phase boundary of the pairing SI transition. This means that the residual entanglement in our mean-field treatment can be used to efficiently capture the signature of the pairing SI transition induced by AMC. Full article

(This article belongs to the Special Issue Topological Phases and Symmetry: Latest Advances and Prospects)

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16 pages, 1612 KB

Open AccessArticle

Strongly Interacting Bose Polarons in Two-Dimensional Atomic Gases and Quantum Fluids of Polaritons

by Luis Fernando Cárdenas-Castillo and Arturo Camacho-Guardian

Atoms 2023, 11(1), 3; https://doi.org/10.3390/atoms11010003 - 29 Dec 2022

Cited by 8 | Viewed by 3921 | Correction

Abstract

Polarons are quasiparticles relevant across many fields in physics: from condensed matter to atomic physics. Here, we study the quasiparticle properties of two-dimensional strongly interacting Bose polarons in atomic Bose–Einstein condensates and polariton gases. Our studies are based on the non-self consistent T-matrix approximation adapted to these physical systems. For the atomic case, we study the spectral and quasiparticle properties of the polaron in the presence of a magnetic Feshbach resonance. We show the presence of two polaron branches: an attractive polaron, a low-lying state that appears as a well-defined quasiparticle for weak attractive interactions, and a repulsive polaron, a metastable state that becomes the dominant branch at weak repulsive interactions. In addition, we study a polaron arising from the dressing of a single itinerant electron by a quantum fluid of polaritons in a semiconductor microcavity. We demonstrate the persistence of the two polaron branches whose properties can be controlled over a wide range of parameters by tuning the cavity mode. Full article

(This article belongs to the Special Issue Recent Trends on Quantum Fluctuations in Ultra-Cold Quantum Gases)

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10 pages, 5861 KB

Open AccessTechnical Note

Design and Construction of Magnetic Coils for Quantum Magnetism Experiments

by Graciana Puentes

Quantum Rep. 2020, 2(3), 378-387; https://doi.org/10.3390/quantum2030026 - 17 Jul 2020

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Abstract

We report on the design and construction of a spin-flip Zeeman slower, a quadrupole magnetic trap and a Feshbach field for a new machine for ultra-cold Li-7. The small mass of the Li-7 atom, and the tight lattice spacing, will enable to achieve a 100-fold increase in tunneling rates over comparable Rb-87 optical lattice emulator experiments. These improvements should enable to access new regimes in quantum magnetic phase transitions and spin dynamics. Full article

(This article belongs to the Special Issue Spin Hall Effect in Photonic Materials)

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15 pages, 4011 KB

Open AccessArticle

A Dual-Species Bose-Einstein Condensate with Attractive Interspecies Interactions

by Alessia Burchianti, Chiara D’Errico, Marco Prevedelli, Luca Salasnich, Francesco Ancilotto, Michele Modugno, Francesco Minardi and Chiara Fort

Condens. Matter 2020, 5(1), 21; https://doi.org/10.3390/condmat5010021 - 21 Mar 2020

Cited by 47 | Viewed by 7097

Abstract

We report on the production of a

^{41}

K-

^{87}

Rb dual-species Bose–Einstein condensate with tunable interspecies interaction and we study the mixture in the attractive regime; i.e., for negative values of the interspecies scattering length

a_{12}

. The binary condensate is [...] Read more.

We report on the production of a

^{41}

K-

^{87}

Rb dual-species Bose–Einstein condensate with tunable interspecies interaction and we study the mixture in the attractive regime; i.e., for negative values of the interspecies scattering length

a_{12}

. The binary condensate is prepared in the ground state and confined in a pure optical trap. We exploit Feshbach resonances for tuning the value of

a_{12}

. After compensating the gravitational sag between the two species with a magnetic field gradient, we drive the mixture into the attractive regime. We let the system evolve both in free space and in an optical waveguide. In both geometries, for strong attractive interactions, we observe the formation of self-bound states, recognizable as quantum droplets. Our findings prove that robust, long-lived droplet states can be realized in attractive two-species mixtures, despite the two atomic components possibly experiencing different potentials. Full article

(This article belongs to the Special Issue SuperFluctuations, 3rd Edition)

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