| 1. |
- Catani, J., et al.
(författare)
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Quantum dynamics of impurities in a one-dimensional Bose gas
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:2
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Tidskriftsartikel (refereegranskat)abstract
- Using a species-selective dipole potential, we create initially localized impurities and investigate their interactions with a majority species of bosonic atoms in a one-dimensional configuration during expansion. We find an interaction-dependent amplitude reduction of the oscillation of the impurities’ size with no measurable frequency shift, and study it as a function of the interaction strength. We discuss possible theoretical interpretations of the data. We compare, in particular, with a polaronic mass shift model derived following Feynman variational approach.
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| 2. |
- Kantian, A., et al.
(författare)
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Competing Regimes of Motion of 1D Mobile Impurities
- 2014
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:7
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Tidskriftsartikel (refereegranskat)abstract
- We show that a distinguishable mobile impurity inside a one-dimensional many-body state at zero temperature generally does not behave like a quasiparticle. Instead, both the impurity dynamics as well as the ground state of the bath are fundamentally transformed by a diverging number of zero-energy excitations being generated, leading to what we call infrared-dominated (ID) dynamics. Combining analytics and density matrix renormalization group numerics, we provide a general formula for the power law governing ID dynamics at zero momentum, discuss a threshold beyond which quasiparticle dynamics may occur again, and study the competition between the ID and quasiparticle universality classes at larger impurity momenta.
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| 3. |
- Kantian, Adrian, et al.
(författare)
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Lattice-Assisted Spectroscopy : A Generalized Scanning Tunneling Microscope for Ultracold Atoms
- 2015
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 115:16
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Tidskriftsartikel (refereegranskat)abstract
- We propose a scheme to measure the frequency-resolved local particle and hole spectra of any optical lattice-confined system of correlated ultracold atoms that offers single-site addressing and imaging, which is now an experimental reality. Combining perturbation theory and time-dependent density matrix renormalization group simulations, we quantitatively test and validate this approach of lattice-assisted spectroscopy on several one-dimensional example systems, such as the superfluid and Mott insulator, with and without a parabolic trap, and finally on edge states of the bosonic Su-Schrieffer-Heeger model. We highlight extensions of our basic scheme to obtain an even wider variety of interesting and important frequency resolved spectra.
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| 4. |
- Kantian, Adrian, 1978-, et al.
(författare)
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Understanding repulsively mediated superconductivity of correlated electrons via massively parallel density matrix renormalization group
- 2019
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 100:7
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Tidskriftsartikel (refereegranskat)abstract
- The so-called minimal models of unconventional superconductivity are lattice models of interacting electrons derived from materials in which electron pairing arises from purely repulsive interactions. Showing unambiguously that a minimal model actually can have a superconducting ground state remains a challenge at nonperturbative interactions. We make a significant step in this direction by computing ground states of the 2D U-V Hubbard model—the minimal model of the quasi-1D superconductors—by parallelized DMRG, which allows for systematic control of any bias and that is sign-problem-free. Using distributed-memory supercomputers and leveraging the advantages of the U-V model, we can treat unprecedented sizes of 2D strips and extrapolate their spin gap both to zero approximation error and the thermodynamic limit. Our results for the spin gap are shown to be compatible with a spin excitation spectrum that is either fully gapped or has zeros only in discrete points, and conversely that a Fermi liquid or magnetically ordered ground state is incompatible with them. Coupled with the enhancement to short-range correlations that we find exclusively in the dxy pairing channel, this allows us to build an indirect case for the ground state of this model having superconducting order in the full 2D limit, and ruling out the other main possible phases, magnetic orders, and Fermi liquids.
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| 5. |
- Massel, F., et al.
(författare)
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Dynamics of an impurity in a one-dimensional lattice
- 2013
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 15:4
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Tidskriftsartikel (refereegranskat)abstract
- We study the non-equilibrium dynamics of an impurity in a harmonic trap that is kicked with a well-defined quasi-momentum, and interacts with a bath of free fermions or interacting bosons in a one-dimensional lattice configuration. Using numerical and analytical techniques we investigate the full dynamics beyond linear response, which allows us to quantitatively characterize states of the impurity in the bath for different parameter regimes. These vary from a tightly bound molecular state in a strongly interacting limit to a polaron (dressed impurity) and a free particle for weak interactions, with composite behaviour in the intermediate regime. These dynamics and different parameter regimes should be readily realizable in systems of cold atoms in optical lattices.
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