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Publications (10 of 29) Show all publications
Wang, W., Díaz-Méndez, R., Wallin, M., Lidmar, J. & Babaev, E. (2019). Melting of a two-dimensional monodisperse cluster crystal to a cluster liquid. Physical review. E, 99(4), Article ID 042140.
Open this publication in new window or tab >>Melting of a two-dimensional monodisperse cluster crystal to a cluster liquid
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2019 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 99, no 4, article id 042140Article in journal (Refereed) Published
Abstract [en]

Monodisperse ensembles of particles that have cluster crystalline phases at low temperatures can model a number of physical systems, such as vortices in type-1.5 superconductors, colloidal suspensions, and cold atoms. In this work, we study a two-dimensional cluster-forming particle system interacting via an ultrasoft potential. We present a simple mean-field characterization of the cluster-crystal ground state, corroborating with Monte Carlo simulations for a wide range of densities. The efficiency of several Monte Carlo algorithms is compared, and the challenges of thermal equilibrium sampling are identified. We demonstrate that the liquid to cluster-crystal phase transition is of first order and occurs in a single step, and the liquid phase is a cluster liquid. © 2019 American Physical Society.

Place, publisher, year, edition, pages
American Physical Society, 2019
Keywords
Ground state, Intelligent systems, Liquids, Suspensions (fluids), Colloidal suspensions, Crystal phase transition, Crystalline phasis, Monodisperse clusters, Monte carlo algorithms, Particle systems, Thermal equilibriums, Two-dimensional clusters, Monte Carlo methods
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-255902 (URN)10.1103/PhysRevE.99.042140 (DOI)000466431600002 ()2-s2.0-85064828694 (Scopus ID)
Note

Export Date: 24 May 2019; Article; Funding details: 621-2012-3984; Funding details: Vetenskapsrådet, 642-2013-7837; Funding text 1: W.W. and E.B. acknowledge support from the Swedish Research Council Grant No. 642-2013-7837 and the Goran Gustafsson Foundation for Research in Natural Sciences and Medicine. M.W. and R.D.M. acknowledge support from the Swedish Research Council Grant No. 621-2012-3984. The computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at the National Supercomputer Centre (NSC) and the High Performance Computing Center North (HPC2N).

Available from: 2019-08-22 Created: 2019-08-22 Last updated: 2019-10-24Bibliographically approved
Diaz-Mendez, R., Pupillo, G., Mezzacapo, F., Wallin, M., Lidmar, J. & Babaev, E. (2019). Phase-change switching in 2D via soft interactions. Soft Matter, 15(3), 355-358
Open this publication in new window or tab >>Phase-change switching in 2D via soft interactions
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2019 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 3, p. 355-358Article in journal (Refereed) Published
Abstract [en]

We present a new type of phase-change behavior relevant for information storage applications, that can be observed in 2D systems with cluster-forming ability. The temperature-based control of the ordering in 2D particle systems depends on the existence of a crystal-to-glass transition. We perform molecular dynamics simulations of models with soft interactions, demonstrating that the crystalline and amorphous structures can be easily tuned by heat pulses. The physical mechanism responsible for this behavior is a self-assembled polydispersity, that depends on the cluster-forming ability of the interactions. Therefore, the range of real materials that can perform such a transition is very wide in nature, ranging from colloidal suspensions to vortex matter. The state of the art in soft matter experimental setups, controlling interactions, polydispersity and dimensionality, makes it a very fertile ground for practical applications.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-244117 (URN)10.1039/c8sm01738g (DOI)000457278300001 ()30556570 (PubMedID)2-s2.0-85060062234 (Scopus ID)
Note

QC 20190219

Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-05-10Bibliographically approved
Wang, W., Wallin, M. & Lidmar, J. (2018). Chaotic temperature and bond dependence of four-dimensional Gaussian spin glasses with partial thermal boundary conditions. Physical review. E, 98(6), Article ID 062122.
Open this publication in new window or tab >>Chaotic temperature and bond dependence of four-dimensional Gaussian spin glasses with partial thermal boundary conditions
2018 (English)In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 98, no 6, article id 062122Article in journal (Refereed) Published
Abstract [en]

Spin glasses have competing interactions and complex energy landscapes that are highly susceptible to perturbations, such as the temperature or the bonds. The thermal boundary condition technique is an effective and visual approach for characterizing chaos and has been successfully applied to three dimensions. In this paper, we tailor the technique to partial thermal boundary conditions, where the thermal boundary condition is applied in a subset (three out of four in this work) of the dimensions for better flexibility and efficiency for a broad range of disordered systems. We use this method to study both temperature chaos and bond chaos of the four-dimensional Edwards-Anderson model with Gaussian disorder to low temperatures. We compare the two forms of chaos, with chaos of three dimensions, and also the four-dimensional +/- J model. We observe that the two forms of chaos are characterized by the same set of scaling exponents, bond chaos is much stronger than temperature chaos, and the exponents are also compatible with the +/- J model. Finally, we discuss the effects of chaos on the number of pure states in the thermal boundary condition ensemble.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-240711 (URN)10.1103/PhysRevE.98.062122 (DOI)000453472900001 ()2-s2.0-85059435644 (Scopus ID)
Note

QC 20190104

Available from: 2019-01-04 Created: 2019-01-04 Last updated: 2019-03-18Bibliographically approved
Diaz-Mendez, R., Lidmar, J. & Wallin, M. (2018). Scaling of the magnetic permeability at the Berezinskii–Kosterlitz–Thouless transition from Coulomb gas simulations. Journal of Statistical Mechanics: Theory and Experiment, 2018(12), Article ID 123203.
Open this publication in new window or tab >>Scaling of the magnetic permeability at the Berezinskii–Kosterlitz–Thouless transition from Coulomb gas simulations
2018 (English)In: Journal of Statistical Mechanics: Theory and Experiment, ISSN 1742-5468, E-ISSN 1742-5468, Vol. 2018, no 12, article id 123203Article in journal (Refereed) Published
Abstract [en]

A new approach to the Berezinskii–Kosterlitz–Thouless transition in the two-dimensional Coulomb gas model is explored by Monte Carlo simulation and finite size scaling. The usual mapping of a neutral two-dimensional superconductor in zero magnetic field to a Coulomb gas leads to an unscreened logarithmic interaction between the vortices, and with periodic boundary conditions vortex configurations are always vorticity neutral with an equal number of plus and minus vortices. We demonstrate that relaxing the neutrality condition has certain advantages. It leads to non-neutral vortex configurations that can appear in real systems with open boundary conditions and permits calculation of the compressibility, which for thin film superconductors corresponds to the magnetic permeability. The vortex-number fluctuation has remarkable scaling properties at and below the Berezinskii–Kosterlitz–Thouless transition. The fugacity variable becomes dangerously irrelevant in the low-temperature phase and leads to a multiplicative scaling correction to the mean-square vortex-number fluctuation and to the magnetic permeability. This multiplicative correction strongly affects the scaling properties of the vorticity fluctuation at and below the transition. Consequences of these findings are demonstrated using Monte Carlo simulations. Inclusion of the next-higher order correction to scaling is found to play an important role in the analysis of numerical data for the vortex number fluctuation and permits accurate determination of the critical properties.

Place, publisher, year, edition, pages
IOP Publishing, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-248133 (URN)10.1088/1742-5468/aae855 (DOI)000452045600003 ()2-s2.0-85059878709 (Scopus ID)
Note

QC 20190513

Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-05-13Bibliographically approved
Eriksson, J., Eriksson, O. S., Maudsdotter, L., Palm, O., Engman, J., Sarkissian, T., . . . Jonsson, A.-B. (2015). Characterization of motility and piliation in pathogenic Neisseria. BMC Microbiology, 15, Article ID 92.
Open this publication in new window or tab >>Characterization of motility and piliation in pathogenic Neisseria
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2015 (English)In: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 15, article id 92Article in journal (Refereed) Published
Abstract [en]

Background: The type IV pili (Tfp) of pathogenic Neisseria (i. e., N. gonorrhoeae and N. meningitidis) are essential for twitching motility. Tfp retraction, which is dependent on the ATPase PilT, generates the forces that move bacteria over surfaces. Neisseria motility has mainly been studied in N. gonorrhoeae whereas the motility of N. meningitidis has not yet been characterized. Results: In this work, we analyzed bacterial motility and monitored Tfp retraction using live- cell imaging of freely moving bacteria. We observed that N. meningitidis moved over surfaces at an approximate speed of 1.6 mu m/s, whereas N. gonorrhoeae moved with a lower speed (1.0 mu/s). An alignment of the meningococcal and gonococcal pilT promoters revealed a conserved single base pair variation in the -10 promoter element that influence PilT expression. By tracking mutants with altered pilT expression or pilE sequence, we concluded that the difference in motility speed was independent of both. Live-cell imaging using total internal reflection fluorescence microscopy demonstrated that N. gonorrhoeae more often moved with fewer visible retracting filaments when compared to N. meningitidis. Correspondingly, meningococci also displayed a higher level of piliation in transmission electron microscopy. Nevertheless, motile gonococci that had the same number of filaments as N. meningitidis still moved with a lower speed. Conclusions: These data reveal differences in both speed and piliation between the pathogenic Neisseria species during twitching motility, suggesting a difference in Tfp-dynamics.

Keywords
Neisseria, Type IV pili, PilT, Twitching motility
National Category
Microbiology
Identifiers
urn:nbn:se:kth:diva-172260 (URN)10.1186/s12866-015-0424-6 (DOI)000355289300001 ()25925502 (PubMedID)2-s2.0-84930644710 (Scopus ID)
Funder
Swedish Research CouncilSwedish Cancer Society
Note

QC 20150819

Available from: 2015-08-19 Created: 2015-08-14 Last updated: 2017-12-04Bibliographically approved
Meier, H., Babaev, E. & Wallin, M. (2015). Fluctuation-induced first order phase transitions in type-1.5 superconductors in zero external field. Physical Review B. Condensed Matter and Materials Physics, 91(9), Article ID 094508.
Open this publication in new window or tab >>Fluctuation-induced first order phase transitions in type-1.5 superconductors in zero external field
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 9, article id 094508Article in journal (Refereed) Published
Abstract [en]

In a single-component Ginzburg-Landau model that possesses thermodynamically stable vortex excitations, the zero-field superconducting phase transition is second order even when fluctuations are included. Beyond the mean-field approximation the transition is described in terms of proliferation of vortex loops. Here we determine the order of the superconducting transition in an effective 3D vortex-loop model for the recently proposed multi-band type-1.5 superconductors where the vortex interaction is non-monotonic, i.e., intermediate-range attractive and short-range repulsive. We find that the details of the vortex interaction, despite its short-range nature, can play an important role for the properties of the transition. In the type-1.5 regime with non-monotonic intervortex interaction, in contrast to the single-band case we find a first-order vortex-driven phase transition.

National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-160964 (URN)10.1103/PhysRevB.91.094508 (DOI)000351426000002 ()2-s2.0-84925859091 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Research Council, 642-2013-7837, 325-2009-7664, 621-2012-3984
Note

QC 20150320

Available from: 2015-03-06 Created: 2015-03-06 Last updated: 2017-12-04Bibliographically approved
Mancarella, F., Balatsky, A. V., Wallin, M. & Rosengren, A. (2013). Angular momentum blockade in nanoscale high-T-c superconducting grains. Superconductors Science and Technology, 26(12)
Open this publication in new window or tab >>Angular momentum blockade in nanoscale high-T-c superconducting grains
2013 (English)In: Superconductors Science and Technology, ISSN 0953-2048, E-ISSN 1361-6668, Vol. 26, no 12Article in journal (Refereed) Published
Abstract [en]

We discuss the angular momentum blockade in small d-wave superconducting grains in an external field. We find that abrupt changes in the angular momentum state of the condensate, angular momentum blockade, occur as a result of changes in the angular momentum of the condensate in an external magnetic field. The effect represents a direct analogy with the Coulomb blockade. We use the Ginzburg-Landau formalism to illustrate how a magnetic field induces a deviation from the d-wave symmetry which is described by a (d(x2-y2)+id(xy))-order parameter. We derive the behavior of the volume magnetic susceptibility as a function of the magnetic field, and corresponding magnetization jumps at critical values of the field that should be experimentally observable in superconducting grains.

Keywords
Angular momentum state, Critical value, External fields, External magnetic field, Ginzburg-Landau formalism, Magnetization jump, Order parameter, Superconducting grains
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-138360 (URN)10.1088/0953-2048/26/12/125014 (DOI)000327447200017 ()2-s2.0-84888372894 (Scopus ID)
Funder
Swedish Research Council, VR 621-2012-298 VR 621-2012-3984EU, European Research Council
Note

QC 20140107

Available from: 2014-01-07 Created: 2013-12-19 Last updated: 2017-12-06Bibliographically approved
Meier, H., Wallin, M. & Teitel, S. (2013). Superfluid transition in a correlated defect network. Physical Review B. Condensed Matter and Materials Physics, 87(21), 214520
Open this publication in new window or tab >>Superfluid transition in a correlated defect network
2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 21, p. 214520-Article in journal (Refereed) Published
Abstract [en]

Motivated by recent experiments on the possible supersolid behavior of He-4 solids at low temperature, we consider a model of superfluidity in a defected solid containing a system spanning network of correlated linear dislocations, or planar grain boundaries. Using arguments based on the Harris criterion, as well as numerical simulations, we find that such correlated quenched disorder shifts the familiar superfluid lambda transition to a new disordered universality class in which the correlation length exponent nu >= 1. This results in the temperature derivatives for the superfluid density d rho(s)/dT and for the heat capacity dc/dT remaining finite at the transition T-c, and thus a less singular transition, profoundly different from the usual lambda transition.

Keywords
Shear Modulus, Helium, Supersolidity, Systems, He-4
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-124723 (URN)10.1103/PhysRevB.87.214520 (DOI)000320999500003 ()2-s2.0-84879697641 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20130730. Updated from "Manuscript" to "Article"

Available from: 2013-07-30 Created: 2013-07-29 Last updated: 2017-12-06Bibliographically approved
Meier, H. & Wallin, M. (2012). Quantum Critical Dynamics Simulation of Dirty Boson Systems. Physical Review Letters, 108(5)
Open this publication in new window or tab >>Quantum Critical Dynamics Simulation of Dirty Boson Systems
2012 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 5Article in journal (Refereed) Published
Abstract [en]

Recently, the scaling result z = d for the dynamic critical exponent at the Bose glass to superfluid quantum phase transition has been questioned both on theoretical and numerical grounds. This motivates a careful evaluation of the critical exponents in order to determine the actual value of z. We study a model of quantum bosons at T = 0 with disorder in 2D using highly effective worm Monte Carlo simulations. Our data analysis is based on a finite-size scaling approach to determine the scaling of the quantum correlation time from simulation data for boson world lines. The resulting critical exponents are z = 1.8 +/- 0.05, nu = 1.15 +/- 0.03, and eta = -0.3 +/- 0.1, hence suggesting that z = 2 is not satisfied.

Keywords
Bose glass, Boson systems, Critical exponent, Dynamic critical exponents, Finite size scaling, Monte Carlo Simulation, Quantum correlations, Quantum critical, Quantum phase transitions, Simulation data
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-50468 (URN)10.1103/PhysRevLett.108.055701 (DOI)000299832900013 ()2-s2.0-84856529164 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20120328. Updated from submitted to published.

Available from: 2011-12-06 Created: 2011-12-06 Last updated: 2019-10-24Bibliographically approved
Lindén, M. & Wallin, M. (2007). Dwell Time Symmetry in Random Walks and Molecular Motors. Biophysical Journal, 92(11), 3804-3816
Open this publication in new window or tab >>Dwell Time Symmetry in Random Walks and Molecular Motors
2007 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 92, no 11, p. 3804-3816Article in journal (Refereed) Published
Abstract [en]

The statistics of steps and dwell times in reversible molecular motors differ from those of cycle completion in enzyme kinetics. The reason is that a step is only one of several transitions in the mechanochemical cycle. As a result, theoretical results for cycle completion in enzyme kinetics do not apply to stepping data. To allow correct parameter estimation, and to guide data analysis and experiment design, a theoretical treatment is needed that takes this observation into account. In this article, we model the distribution of dwell times and number of forward and backward steps using first passage processes, based on the assumption that forward and backward steps correspond to different directions of the same transition. We extend recent results for systems with a single cycle and consider the full dwell time distributions as well as models with multiple pathways, detectable substeps, and detachments. Our main results are a symmetry relation for the dwell time distributions in reversible motors, and a relation between certain relative step frequencies and the free energy per cycle. We demonstrate our results by analyzing recent stepping data for a bacterial flagellar motor, and discuss the implications for the efficiency and reversibility of the force-generating subunits.

Keywords
MYOSIN-V PROCESSIVITY; FLUCTUATION ANALYSIS; KINESIN MOLECULES; FLAGELLAR MOTOR; KINETIC-MODELS; ROTARY MOTOR; F-1-ATPASE; ROTATION; ATP; STEPS
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-8084 (URN)10.1529/biophysj.106.103044 (DOI)000246401800006 ()2-s2.0-34250334739 (Scopus ID)
Note
QC 20100820Available from: 2008-03-07 Created: 2008-03-07 Last updated: 2017-12-14Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1164-0831

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