Article
Physics, Multidisciplinary
Alexander Weitzel, Lea Pfaffinger, Ilaria Maccari, Klaus Kronfeldner, Thomas Huber, Lorenz Fuchs, James Mallord, Sven Linzen, Evgeni Il'Ichev, Nicola Paradiso, Christoph Strunk
Summary: We conducted a comprehensive investigation of the Berezinskii-Kosterlitz-Thouless transition in ultrathin strongly disordered NbN films. Our measurements of resistance, current-voltage characteristics, and kinetic inductance on the same device provide consistent evidence for a sharp unbinding transition of vortex-antivortex pairs, which can be explained by standard renormalization group theory without extra assumptions of inhomogeneity. Our experiments demonstrate that the previously observed broadening of the transition is not intrinsic to strongly disordered superconductors, and provide a clean starting point for studying dynamical effects at the Berezinskii-Kosterlitz-Thouless transition.
PHYSICAL REVIEW LETTERS
(2023)
Article
Optics
Koichiro Furutani, Andrea Perali, Luca Salasnich
Summary: We theoretically investigate the Berezinskii-Kosterlitz-Thouless transition in a binary mixture of bosonic atoms with Rabi coupling. The transition temperature shows a nonmonotonic behavior with respect to the intercomponent coupling and an amplification for finite Rabi coupling. By developing the Nelson-Kosterlitz renormalization-group equations, we clarify the dependence of the transition temperature on the Rabi coupling and the intercomponent coupling. Our results contribute to the understanding of multicomponent quantum systems, such as multiband superconductors.
Article
Physics, Multidisciplinary
G. Dagvadorj, P. Comaron, M. H. Szyma
Summary: We investigate a four-component polariton system in the optical parametric oscillator regime and find that all four components exhibit the same BKT critical point and algebraic decay of spatial coherence. However, the creation of topological defects near the phase transition is largely independent of intercomponent mode locking and strongly depends on the density within a given mode. This unique characteristic allows us to discover a novel state of matter characterized by the proliferation of topological defects on a superfluid with algebraic decay of coherence, which can be observed in current experiments.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
D. Opherden, M. S. J. Tepaske, F. Baertl, M. Weber, M. M. Turnbull, T. Lancaster, S. J. Blundell, M. Baenitz, J. Wosnitza, C. P. Landee, R. Moessner, D. J. Luitz, H. Kuehne
Summary: We report the manifestation of field-induced Berezinskii-Kosterlitz-Thouless (BKT) correlations in the weakly coupled spin-1/2 Heisenberg layers of the molecular-based bulk material. The application of laboratory magnetic fields induces a substantial XY anisotropy of the spin correlations, providing a significant BKT regime. We use nuclear magnetic resonance measurements and quantum Monte Carlo simulations to probe and study the spin correlations.
PHYSICAL REVIEW LETTERS
(2023)
Letter
Chemistry, Multidisciplinary
Arthur Veyrat, Valentin Labracherie, Dima L. Bashlakov, Federico Caglieris, Jorge I. Facio, Grigory Shipunov, Titouan Charvin, Rohith Acharya, Yurii Naidyuk, Romain Giraud, Jeroen van den Brink, Bernd Buechner, Christian Hess, Saicharan Aswartham, Joseph Dufouleur
Summary: In this study, it is predicted that broken inversion symmetry and strong spin-orbit coupling in trigonal PtBi2 lead to a type-I Weyl semimetal band structure. Transport measurements reveal unusually robust low dimensional superconductivity in thin exfoliated flakes of PtBi2, with thickness up to 126 nm and critical temperature (T-c) ranging from 275-400 mK. A Berezinskii-Kosterlitz-Thouless transition with critical temperature (T-BKT) around 310 mK is observed in up to 60 nm thick flakes, which is significantly thicker than rare examples of two-dimensional superconductors exhibiting such a transition. PtBi2 thus provides an ideal platform to study low dimensional and unconventional superconductivity in topological semimetals.
Article
Materials Science, Multidisciplinary
Fernando Gomez-Ortiz, Pablo Garcia-Fernandez, Juan M. Lopez, Javier Junquera
Summary: We investigated the emergence of Berezinskii-Kosterlitz-Thouless (BKT) phases in (PbTiO3)3/(SrTiO3)3 superlattices using second-principles simulations. Under a tensile epitaxial strain of e = 0.25-1%, the local dipole moments within the superlattices are confined to the film-plane, leading to two-dimensional polarization. Our analysis of dipole-dipole correlation decay, density of defects, and temperature dependence supports the existence of a BKT phase, characterized by quasi-long-range order and the presence of tightly bound vortex-antivortex pairs. This proposed superlattice model can be experimentally verified due to its feasibility in fabrication and the imposed mechanical boundary conditions.
Article
Materials Science, Multidisciplinary
Y-H Tseng, F-J Jiang
Summary: By using a supervised neural network trained on a one-dimensional lattice, the study successfully calculated the Berezinskii-Kosterlitz-Thouless phase transitions of two-dimensional classical XY models. The neural network approach proved to be accurate in predicting critical points with minimal information and demonstrated efficiency in computation. This universal neural network is not only valid for symmetry breaking related phase transitions, but also for calculating critical points associated with topology.
RESULTS IN PHYSICS
(2022)
Article
Chemistry, Physical
Wen-He Jiao, Xiao-Feng Xu, Hao Jiang, Zhu-An Xu, Qing-Hu Chen, Guang-Han Cao
Summary: The study demonstrates the presence of BKT transition and Nelson-Kosterlitz jump in high-quality Ba(Fe0.914Co0.086)(2)As-2 single crystals, along with a non-Hall transverse signal exactly at the superconducting transition, which is likely attributed to the guided motion of unbound vortices.
Article
Physics, Multidisciplinary
Guido Giachetti, Nicolo Defenu, Stefano Ruffo, Andrea Trombettoni
Summary: The article discusses the effect of long-range decaying couplings on the BKT transition, revealing a phase diagram far richer than the short-range scenario, with a quasiordered phase existing between a symmetry broken phase and a disordered phase.
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
Krzysztof Gawryluk, Miroslaw Brewczyk
Summary: In this study, the sound propagation in a two-dimensional weakly interacting uniform Bose gas is theoretically explored using classical fields approximation. Density waves generated in both weak and strong perturbation regimes are analyzed, with strong disturbances resulting in a qualitatively different response, identified as quasisolitons. In the strong perturbation regime, quasisolitons break into vortex pairs over time, eventually reaching an equilibrium state characterized by fluctuating in time averaged number of pairs of opposite charge vortices and quasi-long-range order, known as the Berezinskii-Kosterlitz-Thouless (BKT) phase.
SCIENTIFIC REPORTS
(2021)
Article
Materials Science, Multidisciplinary
E. S. Klyushina, J. Reuther, L. Weber, A. T. M. N. Islam, J. S. Lord, B. Klemke, M. Mansson, S. Wessel, B. Lake
Summary: The study revealed that BaNi2V2O8 behaves as a two-dimensional antiferromagnet across the entire temperature range, with different behavior patterns emerging as the temperature increases. Close to the ordering temperature TN, the system behaves as a 2D XY antiferromagnet, while above TN, evidence of Berezinskii-Kosterlitz-Thouless behavior driven by vortex excitations was observed.
Article
Physics, Fluids & Plasmas
Kwai-Kong Ng, Ching-Yu Huang, Feng-Li Lin
Summary: The Berezinskii-Kosterlitz-Thouless (BKT) phase transitions of the two-dimensional q-state clock model with q=4 is studied using the neural network (NN) flow method. The Jensen-Shannon divergence (JSD) is adopted as the information-distance measure thermometer to gauge the difference among Monte Carlo configurations at different temperatures, and to identify the critical temperatures of BKT phase transitions. The results show that the NN flow can flow an arbitrary spin state to a fixed-point ensemble of states, and the JSD of the fixed-point ensemble exhibits unique features.
Article
Materials Science, Multidisciplinary
Domenico Giuliano, Phong H. Nguyen, Andrea Nava, Massimo Boninsegni
Summary: We present a theoretical study on the Berezinskii-Kosterlitz-Thouless transition in a two-dimensional superfluid with an externally imposed density modulation. Using analytical and numerical techniques, we show that as the modulation amplitude increases, the system exhibits behavior similar to the anisotropic x-y model, with a lower superfluid transition temperature and anisotropic response, but no dimensional crossover.
Article
Materials Science, Multidisciplinary
B. Flebus
Summary: The study investigates the interplay between electronic and magnetic degrees of freedom near the BKT transition. By focusing on a metal with easy-plane ferromagnetic order, a framework is established that accounts for the coupling between charge current and the flow of topological magnetic defects, leading to the discovery of a temperature-dependent magnetoresistance effect scaling with the density of topological defects.
Article
Multidisciplinary Sciences
Sujit Sarkar
Summary: The BKT mechanism applies not only to conventional many-body systems, but also to strongly correlated PT symmetry quantum criticality. We observe the presence of hidden QBKT and conventional QBKT for the real part of the potential, with no evidence for the imaginary part. Additionally, we provide exact solutions for the RG flow lines.
SCIENTIFIC REPORTS
(2021)
Article
Chemistry, Physical
Mattia Udina, Jacopo Fiore, Tommaso Cea, Claudio Castellani, Goetz Seibold, Lara Benfatto
Summary: Recent experiments have shown that unconventional cuprate superconductors exhibit an increase in non-linear optical response at temperatures below the superconducting critical temperature. In order to interpret these experimental findings, a theoretical analysis of the various effects contributing to the non-linear response is necessary. This study provides a detailed quantitative analysis of the non-linear THz optical response in cuprates, taking into account the appropriate band structure and disorder level for these systems. The results suggest that the BCS quasiparticle response is the dominant contribution for cuprates, but the polarization dependence of the THz Kerr effect is only partially captured, indicating the presence of additional effects when the system is probed using light pulses with different central frequencies.
FARADAY DISCUSSIONS
(2022)
Article
Materials Science, Multidisciplinary
C. Martens, G. Seibold
Summary: In this study, the time-dependent Gutzwiller approximation is used to analyze the non-equilibrium dynamics of the single-band Hubbard model, focusing on the interplay between spin and charge dynamics. By quenching the system in either the charge or spin sector, the coupled relaxation dynamics as a function of supplied energy is investigated. Mapping the Gutzwiller dynamics onto a time-dependent Landau approach provides further insight into tuning the coupling between spin and charge degrees of freedom.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Physics, Multidisciplinary
Sergio Caprara, Carlo Di Castro, Giovanni Mirarchi, Goetz Seibold, Marco Grilli
Summary: Fermi-liquid theory has been successful in describing the behavior of metals, but there are cases, like high-temperature superconductors, where it fails. The authors identify parameters that could be responsible for this strange behavior and explore how it impacts resistivity and specific heat measurements.
COMMUNICATIONS PHYSICS
(2022)
Article
Physics, Condensed Matter
Giovanni Mirarchi, Gotz Seibold, Carlo Di Castro, Marco Grilli, Sergio Caprara
Summary: Recent research has identified charge density fluctuations as a key factor in the anomalous transport properties of cuprates in the strange-metal phase. This provides a microscopic scattering mechanism and contributes to anomalies in specific heat.
Article
Multidisciplinary Sciences
Anand Kamlapure, Manuel Simonato, Emil Sierda, Manuel Steinbrecher, Umut Kamber, Elze J. Knol, Peter Krogstrup, Mikhail Katsnelson, Malte Roesner, Alexander Ako Khajetoorians
Summary: The influence of interface electronic structure is crucial for controlling lower dimensional superconductivity. In this study, the authors demonstrate that the hybrid electronic structure formed at the interface between a lead film and a black phosphorus substrate significantly alters the superconductivity in the lead film.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Marco Grilli, Carlo Di Castro, Giovanni Mirarchi, Goetz Seibold, Sergio Caprara
Summary: The strange metal behavior, characterized by linear-in-temperature resistivity, is still a mystery in solid-state physics. It is often associated with a quantum critical point and the divergence of order parameter correlation length. This study proposes a paradigm shift, focusing on a divergent characteristic time scale due to divergent dissipation in critical modes, while their correlation length remains finite. A mechanism based on the coupling between local order parameter fluctuations and electron density diffusive modes is proposed to explain the linear-in-T resistivity and logarithmic specific heat versus temperature ratio down to low temperatures.
Article
Multidisciplinary Sciences
Werner M. J. van Weerdenburg, Anand Kamlapure, Eirik Holm Fyhn, Xiaochun Huang, Niels P. E. van Mullekom, Manuel Steinbrecher, Peter Krogstrup, Jacob Linder, Alexander Ako Khajetoorians
Summary: We observe a threefold enhancement of the superconducting critical temperature and gap size in ultrathin epitaxial Al films on Si(111) approaching the 2D limit. We characterize the vortex structure using spatially resolved spectroscopy and find evidence of a paramagnetic Meissner effect originating from odd-frequency pairing contributions. These results highlight the influences of reduced dimensionality on a BCS superconductor and provide a platform for studying BCS superconductivity in large magnetic fields.
Article
Materials Science, Multidisciplinary
I. Maccari, Bal K. Pokharel, J. Terzic, J. Jesudasan, Surajit Dutta, Pratap Raychaudhuri, J. Lorenzana, C. De Michele, C. Castellani, L. Benfatto, Dragana Popovic
Summary: In a two-dimensional superconducting vortex lattice, melting from solid to isotropic liquid occurs via an intermediate phase with orientational correlations. The impact of such correlations on transport and their interaction with quenched disorder are still unknown.
Article
Materials Science, Multidisciplinary
Rishabh Duhan, Subhamita Sengupta, Ruchi Tomar, Somak Basistha, Vivas Bagwe, Chandan Dasgupta, Pratap Raychaudhuri
Summary: We report the formation of a pinned vortex liquid in a 5-nm-thick amorphous superconducting film, where some vortices remain static while others form a percolating network.
Article
Materials Science, Multidisciplinary
Jacopo Fiore, Mattia Udina, Marco Marciani, Goetz Seibold, Lara Benfatto
Summary: This study investigates the spectrum of collective amplitude fluctuations in a clean two-band superconductor and reveals its differences compared to the single-band case. The nonlinear optical response in MgB2 is critically analyzed, explaining the contradictory results of recent experiments. The relative contribution of quasiparticle, amplitude, and phase fluctuations to the nonlinear optical response is computed through numerical simulations and realistic estimates of disorder.
Article
Materials Science, Multidisciplinary
Marco Marciani, Lara Benfatto
Summary: In this study, we compute the resistivity anisotropy in the nematic phase of FeSe using the static solution of the multiorbital Boltzmann equation. We introduce disorder at the microscopic multiorbital model level and demonstrate that even elastic scattering by localized impurities can lead to nontrivial anisotropic renormalization of the electronic velocities, challenging the conventional understanding of transport based on cold- and hot-spots effects. Our model considers both the xz/yz and the recently proposed xy nematic ordering, and we show that the latter plays a crucial role in reproducing the experimentally observed anisotropy, providing a direct fingerprint of different nematic scenarios on the bulk transport property of FeSe.
Article
Materials Science, Multidisciplinary
G. Seibold, C. Castellani, J. Lorenzana
Summary: In this study, an adiabatic transition from a BCS superconductor to a Fermi liquid is investigated. It is found that the Fermi liquid can retain a memory of the parent BCS state and can be recovered through a specific operation. Furthermore, the evolution of the order parameter phase phi is studied and its role in restoring the noninteracting chemical potential and gauge-invariant current response is analyzed.
Article
Physics, Multidisciplinary
F. Gabriele, C. Castellani, L. Benfatto
Summary: This study provides a complete description of generalized plasma waves in layered superconductors, in terms of gauge-invariant superconducting phase, by considering both the Coulomb interaction and relativistic effects. The research finds that the anisotropy of the superfluid response leads to two intertwined hybrid light-matter modes, and at a specific scale, these two modes appear with equal weight.
PHYSICAL REVIEW RESEARCH
(2022)
