TY - JOUR
AB - It is a common knowledge that an effective interaction of a quantum impurity with an electromagnetic field can be screened by surrounding charge carriers, whether mobile or static. Here we demonstrate that very strong, "anomalous" screening can take place in the presence of a neutral, weakly polarizable environment, due to an exchange of orbital angular momentum between the impurity and the bath. Furthermore, we show that it is possible to generalize all phenomena related to isolated impurities in an external field to the case when a many-body environment is present, by casting the problem in terms of the angulon quasiparticle. As a result, the relevant observables such as the effective Rabi frequency, geometric phase, and impurity spatial alignment are straightforward to evaluate in terms of a single parameter: the angular-momentum-dependent screening factor.
AU - Yakaboylu, Enderalp
AU - Lemeshko, Mikhail
ID - 1133
IS - 8
JF - Physical Review Letters
SN - 00319007
TI - Anomalous screening of quantum impurities by a neutral environment
VL - 118
ER -
TY - JOUR
AB - Selected universal experimental properties of high-temperature superconducting (HTS) cuprates have been singled out in the last decade. One of the pivotal challenges in this field is the designation of a consistent interpretation framework within which we can describe quantitatively the universal features of those systems. Here we analyze in a detailed manner the principal experimental data and compare them quantitatively with the approach based on a single-band model of strongly correlated electrons supplemented with strong antiferromagnetic (super)exchange interaction (the so-called t−J−U model). The model rationale is provided by estimating its microscopic parameters on the basis of the three-band approach for the Cu-O plane. We use our original full Gutzwiller wave-function solution by going beyond the renormalized mean-field theory (RMFT) in a systematic manner. Our approach reproduces very well the observed hole doping (δ) dependence of the kinetic-energy gain in the superconducting phase, one of the principal non-Bardeen-Cooper-Schrieffer features of the cuprates. The calculated Fermi velocity in the nodal direction is practically δ-independent and its universal value agrees very well with that determined experimentally. Also, a weak doping dependence of the Fermi wave vector leads to an almost constant value of the effective mass in a pure superconducting phase which is both observed in experiment and reproduced within our approach. An assessment of the currently used models (t−J, Hubbard) is carried out and the results of the canonical RMFT as a zeroth-order solution are provided for comparison to illustrate the necessity of the introduced higher-order contributions.
AU - Spałek, Jozef
AU - Zegrodnik, Michał
AU - Kaczmarczyk, Jan
ID - 1162
IS - 2
JF - Physical Review B - Condensed Matter and Materials Physics
SN - 24699950
TI - Universal properties of high temperature superconductors from real space pairing t-J-U model and its quantitative comparison with experiment
VL - 95
ER -
TY - JOUR
AB - We investigate the effect of the electron-hole (e-h) symmetry breaking on d-wave superconductivity induced by non-local effects of correlations in the generalized Hubbard model. The symmetry breaking is introduced in a two-fold manner: by the next-to-nearest neighbor hopping of electrons and by the charge-bond interaction - the off-diagonal term of the Coulomb potential. Both terms lead to a pronounced asymmetry of the superconducting order parameter. The next-to-nearest neighbor hopping enhances superconductivity for h-doping, while diminishes it for e-doping. The charge-bond interaction alone leads to the opposite effect and, additionally, to the kinetic-energy gain upon condensation in the underdoped regime. With both terms included, with similar amplitudes, the height of the superconducting dome and the critical doping remain in favor of h-doping. The influence of the charge-bond interaction on deviations from symmetry of the shape of the gap at the Fermi surface in the momentum space is briefly discussed.
AU - Wysokiński, Marcin
AU - Kaczmarczyk, Jan
ID - 1163
IS - 8
JF - Journal of Physics: Condensed Matter
SN - 09538984
TI - Unconventional superconductivity in generalized Hubbard model role of electron–hole symmetry breaking terms
VL - 29
ER -
TY - JOUR
AB - In science, as in life, "surprises" can be adequately appreciated only in the presence of a null model, what we expect a priori. In physics, theories sometimes express the values of dimensionless physical constants as combinations of mathematical constants like π or e. The inverse problem also arises, whereby the measured value of a physical constant admits a "surprisingly" simple approximation in terms of well-known mathematical constants. Can we estimate the probability for this to be a mere coincidence, rather than an inkling of some theory? We answer the question in the most naive form.
AU - Amir, Ariel
AU - Lemeshko, Mikhail
AU - Tokieda, Tadashi
ID - 1204
IS - 6
JF - American Mathematical Monthly
TI - Surprises in numerical expressions of physical constants
VL - 123
ER -
TY - JOUR
AB - We study a polar molecule immersed in a superfluid environment, such as a helium nanodroplet or a Bose–Einstein condensate, in the presence of a strong electrostatic field. We show that coupling of the molecular pendular motion, induced by the field, to the fluctuating bath leads to formation of pendulons—spherical harmonic librators dressed by a field of many-particle excitations. We study the behavior of the pendulon in a broad range of molecule–bath and molecule–field interaction strengths, and reveal that its spectrum features a series of instabilities which are absent in the field-free case of the angulon quasiparticle. Furthermore, we show that an external field allows to fine-tune the positions of these instabilities in the molecular rotational spectrum. This opens the door to detailed experimental studies of redistribution of orbital angular momentum in many-particle systems. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
AU - Redchenko, Elena
AU - Lemeshko, Mikhail
ID - 1206
IS - 22
JF - ChemPhysChem
TI - Libration of strongly oriented polar molecules inside a superfluid
VL - 17
ER -
TY - JOUR
AB - We use recently developed angulon theory [R. Schmidt and M. Lemeshko, Phys. Rev. Lett. 114, 203001 (2015)PRLTAO0031-900710.1103/PhysRevLett.114.203001] to study the rotational spectrum of a cyanide molecular anion immersed into Bose-Einstein condensates of rubidium and strontium. Based on ab initio potential energy surfaces, we provide a detailed study of the rotational Lamb shift and many-body-induced fine structure which arise due to dressing of molecular rotation by a field of phonon excitations. We demonstrate that the magnitude of these effects is large enough in order to be observed in modern experiments on cold molecular ions. Furthermore, we introduce a novel method to construct pseudopotentials starting from the ab initio potential energy surfaces, which provides a means to obtain effective coupling constants for low-energy polaron models.
AU - Midya, Bikashkali
AU - Tomza, Michał
AU - Schmidt, Richard
AU - Lemeshko, Mikhail
ID - 1286
IS - 4
JF - Physical Review A - Atomic, Molecular, and Optical Physics
TI - Rotation of cold molecular ions inside a Bose-Einstein condensate
VL - 94
ER -
TY - JOUR
AB - A planar waveguide with an impedance boundary, composed of nonperfect metallic plates, and with passive or active dielectric filling, is considered. We show the possibility of selective mode guiding and amplification when a homogeneous pump is added to the dielectric and analyze differences in TE and TM mode propagation. Such a non-conservative system is also shown to feature exceptional points for specific and experimentally tunable parameters, which are described for a particular case of transparent dielectric.
AU - Midya, Bikashkali
AU - Konotop, Vladimir
ID - 1287
IS - 20
JF - Optics Letters
TI - Modes and exceptional points in waveguides with impedance boundary conditions
VL - 41
ER -
TY - JOUR
AB - The Fermi-Hubbard model is one of the key models of condensed matter physics, which holds a
potential for explaining the mystery of high-temperature superconductivity. Recent progress in
ultracold atoms in optical lattices has paved the way to studying the model’s phase diagram using
the tools of quantum simulation, which emerged as a promising alternative to the numerical
calculations plagued by the infamous sign problem. However, the temperatures achieved using
elaborate laser cooling protocols so far have been too high to show the appearance of
antiferromagnetic (AF) and superconducting quantum phases directly. In this work, we demonstrate
that using the machinery of dissipative quantum state engineering, one can observe the emergence of
the AF order in the Fermi-Hubbard model with fermions in optical lattices. The core of the approach
is to add incoherent laser scattering in such a way that the AF state emerges as the dark state of
the driven-dissipative dynamics. The proposed controlled dissipation channels described in this work
are straightforward to add to already existing experimental setups.
AU - Kaczmarczyk, Jan
AU - Weimer, Hendrik
AU - Lemeshko, Mikhail
ID - 1343
IS - 9
JF - New Journal of Physics
TI - Dissipative preparation of antiferromagnetic order in the Fermi-Hubbard model
VL - 18
ER -
TY - JOUR
AB - During the past 70 years, the quantum theory of angular momentum has been successfully applied to describing the properties of nuclei, atoms, and molecules, and their interactions with each other as well as with external fields. Because of the properties of quantum rotations, the angular-momentum algebra can be of tremendous complexity even for a few interacting particles, such as valence electrons of an atom, not to mention larger many-particle systems. In this work, we study an example of the latter: A rotating quantum impurity coupled to a many-body bosonic bath. In the regime of strong impurity-bath couplings, the problem involves the addition of an infinite number of angular momenta, which renders it intractable using currently available techniques. Here, we introduce a novel canonical transformation that allows us to eliminate the complex angular-momentum algebra from such a class of many-body problems. In addition, the transformation exposes the problem's constants of motion, and renders it solvable exactly in the limit of a slowly rotating impurity. We exemplify the technique by showing that there exists a critical rotational speed at which the impurity suddenly acquires one quantum of angular momentum from the many-particle bath. Such an instability is accompanied by the deformation of the phonon density in the frame rotating along with the impurity.
AU - Schmidt, Richard
AU - Lemeshko, Mikhail
ID - 1347
IS - 1
JF - Physical Review X
TI - Deformation of a quantum many-particle system by a rotating impurity
VL - 6
ER -
TY - JOUR
AB - We study the interplay of nematic and superconducting order in the two-dimensional Hubbard model and show that they can coexist, especially when superconductivity is not the energetically dominant phase. Due to a breaking of the C4 symmetry, the coexisting phase inherently contains admixture of the s-wave pairing components. As a result, the superconducting gap exhibits nonstandard features including changed nodal directions. Our results also show that in the optimally doped regime the pure superconducting phase is typically unstable towards developing nematicity (breaking of the C4 symmetry). This has implications for the cuprate high-Tc superconductors, for which in this regime the so-called intertwined orders have recently been observed. Namely, the coexisting phase may be viewed as a precursor to such more involved patterns of symmetry breaking.
AU - Kaczmarczyk, Jan
AU - Schickling, Tobias
AU - Bünemann, Jörg
ID - 1352
IS - 8
JF - Physical Review B - Condensed Matter and Materials Physics
TI - Coexistence of nematic order and superconductivity in the Hubbard model
VL - 94
ER -
TY - JOUR
AB - Superconductivity in heavy-fermion systems has an unconventional nature and is considered to originate from the universal features of the electronic structure. Here, the Anderson lattice model is studied by means of the full variational Gutzwiller wave function incorporating nonlocal effects of the on-site interaction. We show that the d-wave superconducting ground state can be driven solely by interelectronic correlations. The proposed microscopic mechanism leads to a multigap superconductivity with the dominant contribution due to f electrons and in the dx2−y2-wave channel. Our results rationalize several important observations for CeCoIn5.
AU - Wysokiński, Marcin
AU - Kaczmarczyk, Jan
AU - Spałek, Jozef
ID - 1368
IS - 2
JF - Physical Review B - Condensed Matter and Materials Physics
TI - Correlation driven d wave superconductivity in Anderson lattice model: Two gaps
VL - 94
ER -
TY - JOUR
AB - Anisotropic dipole-dipole interactions between ultracold dipolar fermions break the symmetry of the Fermi surface and thereby deform it. Here we demonstrate that such a Fermi surface deformation induces a topological phase transition - the so-called Lifshitz transition - in the regime accessible to present-day experiments. We describe the impact of the Lifshitz transition on observable quantities such as the Fermi surface topology, the density-density correlation function, and the excitation spectrum of the system. The Lifshitz transition in ultracold atoms can be controlled by tuning the dipole orientation and, in contrast to the transition studied in crystalline solids, is completely interaction driven.
AU - Van Loon, Erik
AU - Katsnelson, Mikhail
AU - Chomaz, Lauriane
AU - Lemeshko, Mikhail
ID - 1416
IS - 19
JF - Physical Review B - Condensed Matter and Materials Physics
TI - Interaction-driven Lifshitz transition with dipolar fermions in optical lattices
VL - 93
ER -
TY - JOUR
AB - We study the superconducting phase of the Hubbard model using the Gutzwiller variational wave function (GWF) and the recently proposed diagrammatic expansion technique (DE-GWF). The DE-GWF method works on the level of the full GWF and in the thermodynamic limit. Here, we consider a finite-size system to study the accuracy of the results as a function of the system size (which is practically unrestricted). We show that the finite-size scaling used, e.g. in the variational Monte Carlo method can lead to significant, uncontrolled errors. The presented research is the first step towards applying the DE-GWF method in studies of inhomogeneous situations, including systems with impurities, defects, inhomogeneous phases, or disorder.
AU - Tomski, Andrzej
AU - Kaczmarczyk, Jan
ID - 1419
IS - 17
JF - Journal of Physics: Condensed Matter
TI - Gutzwiller wave function for finite systems: Superconductivity in the Hubbard model
VL - 28
ER -
TY - JOUR
AB - The two-photon 1s2 2s 2p 3P0 1s22s2 1S0 transition in berylliumlike ions is theoretically investigated within a fully relativistic framework and a second-order perturbation theory. We focus our analysis on how electron correlation, as well as the negative-energy spectrum, can affect the forbidden E1M1 decay rate. For this purpose, we include the electronic correlation via an effective local potential and within a single configuration-state model. Due to its experimental interest, evaluations of decay rates are performed for berylliumlike xenon and uranium. We find that the negative-energy contribution can be neglected at the present level of accuracy in the evaluation of the decay rate. On the other hand, if contributions of electronic correlation are not carefully taken into account, it may change the lifetime of the metastable state by up to 20%. By performing a full-relativistic jj-coupling calculation, we found a decrease of the decay rate by two orders of magnitude compared to non-relativistic LS-coupling calculations, for the selected heavy ions.
AU - Amaro, Pedro
AU - Fratini, Filippo
AU - Safari, Laleh
AU - Machado, Jorge
AU - Guerra, Mauro
AU - Indelicato, Paul
AU - Santos, José
ID - 1496
IS - 3
JF - Physical Review A - Atomic, Molecular, and Optical Physics
TI - Relativistic evaluation of the two-photon decay of the metastable 1s22s2p3P0 state in berylliumlike ions with an effective-potential model
VL - 93
ER -
TY - JOUR
AB - We investigate the quantum interference shifts between energetically close states, where the state structure is observed by laser spectroscopy. We report a compact and analytical expression that models the quantum interference induced shift for any admixture of circular polarization of the incident laser and angle of observation. An experimental scenario free of quantum interference can thus be predicted with this formula. Although this study is exemplified here for muonic deuterium, it can be applied to any other laser spectroscopy measurement of ns-n′p frequencies of a nonrelativistic atomic system, via an ns→n′p→n′′s scheme.
AU - Amaro, Pedro
AU - Fratini, Filippo
AU - Safari, Laleh
AU - Antognini, Aldo
AU - Indelicato, Paul
AU - Pohl, Randolf
AU - Santos, José
ID - 1587
IS - 6
JF - Physical Review A - Atomic, Molecular, and Optical Physics
TI - Quantum interference shifts in laser spectroscopy with elliptical polarization
VL - 92
ER -
TY - JOUR
AB - Quantum interference between energetically close states is theoretically investigated, with the state structure being observed via laser spectroscopy. In this work, we focus on hyperfine states of selected hydrogenic muonic isotopes, and on how quantum interference affects the measured Lamb shift. The process of photon excitation and subsequent photon decay is implemented within the framework of nonrelativistic second-order perturbation theory. Due to its experimental interest, calculations are performed for muonic hydrogen, deuterium, and helium-3. We restrict our analysis to the case of photon scattering by incident linear polarized photons and the polarization of the scattered photons not being observed. We conclude that while quantum interference effects can be safely neglected in muonic hydrogen and helium-3, in the case of muonic deuterium there are resonances with close proximity, where quantum interference effects can induce shifts up to a few percent of the linewidth, assuming a pointlike detector. However, by taking into account the geometry of the setup used by the CREMA collaboration, this effect is reduced to less than 0.2% of the linewidth in all possible cases, which makes it irrelevant at the present level of accuracy. © 2015 American Physical Society.
AU - Amaro, Pedro
AU - Franke, Beatrice
AU - Krauth, Julian
AU - Diepold, Marc
AU - Fratini, Filippo
AU - Safari, Laleh
AU - Machado, Jorge
AU - Antognini, Aldo
AU - Kottmann, Franz
AU - Indelicato, Paul
AU - Pohl, Randolf
AU - Santos, José
ID - 1693
IS - 2
JF - Physical Review A
TI - Quantum interference effects in laser spectroscopy of muonic hydrogen, deuterium, and helium-3
VL - 92
ER -
TY - JOUR
AB - We give a comprehensive introduction into a diagrammatic method that allows for the evaluation of Gutzwiller wave functions in finite spatial dimensions. We discuss in detail some numerical schemes that turned out to be useful in the real-space evaluation of the diagrams. The method is applied to the problem of d-wave superconductivity in a two-dimensional single-band Hubbard model. Here, we discuss in particular the role of long-range contributions in our diagrammatic expansion. We further reconsider our previous analysis on the kinetic energy gain in the superconducting state.
AU - Kaczmarczyk, Jan
AU - Schickling, Tobias
AU - Bünemann, Jörg
ID - 1695
IS - 9
JF - Physica Status Solidi (B): Basic Solid State Physics
TI - Evaluation techniques for Gutzwiller wave functions in finite dimensions
VL - 252
ER -
TY - JOUR
AB - The recently proposed diagrammatic expansion (DE) technique for the full Gutzwiller wave function (GWF) is applied to the Anderson lattice model. This approach allows for a systematic evaluation of the expectation values with full Gutzwiller wave function in finite-dimensional systems. It introduces results extending in an essential manner those obtained by means of the standard Gutzwiller approximation (GA), which is variationally exact only in infinite dimensions. Within the DE-GWF approach we discuss the principal paramagnetic properties and their relevance to heavy-fermion systems. We demonstrate the formation of an effective, narrow f band originating from atomic f-electron states and subsequently interpret this behavior as a direct itineracy of f electrons; it represents a combined effect of both the hybridization and the correlations induced by the Coulomb repulsive interaction. Such a feature is absent on the level of GA, which is equivalent to the zeroth order of our expansion. Formation of the hybridization- and electron-concentration-dependent narrow f band rationalizes the common assumption of such dispersion of f levels in the phenomenological modeling of the band structure of CeCoIn5. Moreover, it is shown that the emerging f-electron direct itineracy leads in a natural manner to three physically distinct regimes within a single model that are frequently discussed for 4f- or 5f-electron compounds as separate model situations. We identify these regimes as (i) the mixed-valence regime, (ii) Kondo/almost-Kondo insulating regime, and (iii) the Kondo-lattice limit when the f-electron occupancy is very close to the f-state half filling, ⟨nˆf⟩→1. The nonstandard features of the emerging correlated quantum liquid state are stressed.
AU - Wysokiński, Marcin
AU - Kaczmarczyk, Jan
AU - Spałek, Jozef
ID - 1696
IS - 12
JF - Physical Review B
TI - Gutzwiller wave function solution for Anderson lattice model: Emerging universal regimes of heavy quasiparticle states
VL - 92
ER -
TY - JOUR
AB - We use the dual boson approach to reveal the phase diagram of the Fermi-Hubbard model with long-range dipole-dipole interactions. By using a large-scale finite-temperature calculation on a 64×64 square lattice we demonstrate the existence of a novel phase, possessing an "ultralong-range" order. The fingerprint of this phase - the density correlation function - features a nontrivial behavior on a scale of tens of lattice sites. We study the properties and the stability of the ultralong-range-ordered phase, and show that it is accessible in modern experiments with ultracold polar molecules and magnetic atoms.
AU - Van Loon, Erik
AU - Katsnelson, Mikhail
AU - Lemeshko, Mikhail
ID - 1700
IS - 8
JF - Physical Review B
TI - Ultralong-range order in the Fermi-Hubbard model with long-range interactions
VL - 92
ER -
TY - JOUR
AB - Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.
AU - Safari, Laleh
AU - Santos, José
AU - Amaro, Pedro
AU - Jänkälä, Kari
AU - Fratini, Filippo
ID - 1811
IS - 5
JF - Journal of Mathematical Physics
TI - Analytical evaluation of atomic form factors: Application to Rayleigh scattering
VL - 56
ER -