Change search
Refine search result
1 - 11 of 11
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Atteia, J.
    et al.
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cayssol, J.
    Ballistic transport through irradiated graphene2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 24, article id 245404Article in journal (Refereed)
    Abstract [en]

    The coherent charge transport through an illuminated graphene ribbon is studied as a function of electronic doping and characteristics of the electromagnetic driving, for monochromatic circularly polarized light. We focus on the DC current carried by 2D bulk carriers which is dominant (over edge transport) for short and wide enough samples. We investigate how the ballistic conductance suppression, due to photon resonances between the valence and conduction bands, evolves when the experimentally tunable parameters are varied. The residual conductance can be associated with evanescent states and related to dynamical gaps in the Floquet quasienergy spectrum.

  • 2. Behrends, Jan
    et al.
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. Max Planck Institute, Germany.
    Strongly angle-dependent magnetoresistance in Weyl semimetals with long-range disorder2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 6, article id 060201Article in journal (Refereed)
    Abstract [en]

    The chiral anomaly in Weyl semimetals states that the left- and right-handed Weyl fermions, constituting the low energy description, are not individually conserved, resulting, for example, in a negative magnetoresistance in such materials. Recent experiments see strong indications of such an anomalous resistance response; however, with a response that at strong fields is more sharply peaked for parallel magnetic and electric fields than expected from simple theoretical considerations. Here, we uncover a mechanism, arising from the interplay between the angle-dependent Landau-level structure and long-range scalar disorder, that has the same phenomenology. In particular, we analytically show, and numerically confirm, that the internode scattering time decreases exponentially with the angle between the magnetic field and the Weyl node separation in the large field limit, while it is insensitive to this angle at weak magnetic fields. Since, in the simplest approximation, the internode scattering time is proportional to the anomaly-related conductivity, this feature may be related to the experimental observations of a sharply peaked magnetoresistance.

  • 3. Behrends, Jan
    et al.
    Rhim, Jun-Won
    Liu, Shang
    Grushin, Adolfo G.
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. Max-Planck-Institut für Physik Komplexer Systeme, Germany.
    Nodal-line semimetals from Weyl superlattices2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 24, article id 245101Article in journal (Refereed)
    Abstract [en]

    The existence and topological classification of lower-dimensional Fermi surfaces is often tied to the crystal symmetries of the underlying lattice systems. Artificially engineered lattices, such as heterostructures and other superlattices, provide promising avenues to realize desired crystal symmetries that protect lower-dimensional Fermi surfaces, such as nodal lines. In this work, we investigate a Weyl semimetal subjected to spatially periodic onsite potential, giving rise to several phases, including a nodal-line semimetal phase. In contrast to proposals that purely focus on lattice symmetries, the emergence of the nodal line in this setup does not require small spin-orbit coupling, but rather relies on its presence. We show that the stability of the nodal line is understood from reflection symmetry and a combination of a fractional lattice translation and charge-conjugation symmetry. Depending on the choice of parameters, this model exhibits drumhead surface states that are exponentially localized at the surface, or weakly localized surface states that decay into the bulk at all energies.

  • 4. Bera, Soumya
    et al.
    Martynec, Thomas
    Schomerus, Henning
    Heidrich-Meisner, Fabian
    Hjörleifur Bardarson, Jens
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. Max-Planck-Institut für Physik komplexer Systeme, Germany.
    One-particle density matrix characterization of many-body localization2017In: Annalen der Physik, ISSN 0003-3804, E-ISSN 1521-3889, Vol. 529, no 7, article id 1600356Article in journal (Refereed)
    Abstract [en]

    We study interacting fermions in one dimension subject to random, uncorrelated onsite disorder, a paradigmatic model of many-body localization (MBL). This model realizes an interaction-driven quantum phase transition between an ergodic and a many-body localized phase, with the transition occurring in the many-body eigenstates. We propose a single-particle framework to characterize these phases by the eigenstates (the natural orbitals) and the eigenvalues (the occupation spectrum) of the one-particle density matrix (OPDM) in individual many-body eigenstates. As a main result, we find that the natural orbitals are localized in the MBL phase, but delocalized in the ergodic phase. This qualitative change in these single-particle states is a many-body effect, since without interactions the single-particle energy eigenstates are all localized. The occupation spectrum in the ergodic phase is thermal in agreement with the eigenstate thermalization hypothesis, while in the MBL phase the occupations preserve a discontinuity at an emergent Fermi edge. This suggests that the MBL eigenstates are weakly dressed Slater determinants, with the eigenstates of the underlying Anderson problem as reference states. We discuss the statistical properties of the natural orbitals and of the occupation spectrum in the two phases and as the transition is approached. Our results are consistent with the existing picture of emergent integrability and localized integrals of motion, or quasiparticles, in the MBL phase. We emphasize the close analogy of the MBL phase to a zero-temperature Fermi liquid: in the studied model, the MBL phase is adiabatically connected to the Anderson insulator and the occupation-spectrum discontinuity directly indicates the presence of quasiparticles localized in real space. Finally, we show that the same picture emerges for interacting fermions in the presence of an experimentally-relevant bichromatic lattice and thereby demonstrate that our findings are not limited to a specific model.

  • 5. Dufouleur, J.
    et al.
    Xypakis, E.
    Buechner, B.
    Giraud, R.
    Bardarson, Jens Hjörleifur
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. Max Planck Institute for Physics - Max-Planck-Gesellschaft, Germany.
    Suppression of scattering in quantum confined 2D helical Dirac systems2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 7, article id 075401Article in journal (Refereed)
    Abstract [en]

    Transport properties of helical Dirac fermions in disordered quantum wires are investigated in the large energy limit. In the quasiballistic regime, the conductance and the Fano factor are sensitive to disorder only when the Fermi energy is close to an opening of a transverse mode. In the limit of a large number of transverse modes, transport properties are insensitive to the geometry of the nanowire or the nature and strength of the disorder but, instead, are dominated by the properties of the interface between the ohmic contact and the nanowire. In the case of a heavily doped Dirac metallic contact, the conductance is proportional to the energy with an average transmission T = pi/4 and a Fano factor of F similar or equal to 0.13. Those results can be generalized to a much broader class of contacts, the exact values of T and F depending on the model used for the contacts. The energy dependence of Aharonov-Bohm oscillations is determined, revealing a damped oscillatory behavior and phase shifts due to the one-dimensional subband quantization and which are not the signature of the nontrivial topology.

  • 6. Erlingsson, S. I.
    et al.
    Bardarson, Jens Hjörleifur
    KTH, School of Engineering Sciences (SCI), Physics.
    Manolescu, A.
    Thermoelectric current in topological insulator nanowires with impurities2018In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 9, no 1, p. 1156-1161Article in journal (Refereed)
    Abstract [en]

    In this paper we consider charge current generated by maintaining a temperature difference over a nanowire at zero voltage bias. For topological insulator nanowires in a perpendicular magnetic field the current can change sign as the temperature of one end is increased. Here we study how this thermoelectric current sign reversal depends on the magnetic field and how impurities affect the size of the thermoelectric current. We consider both scalar and magnetic impurities and show that their influence on the current are quite similar, although the magnetic impurities seem to be more effective in reducing the effect. For moderate impurity concentration the sign reversal persists.

  • 7. Erlingsson, Sigurdur I.
    et al.
    Manolescu, Andrei
    Nemnes, George Alexandru
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Sanchez, David
    Reversal of Thermoelectric Current in Tubular Nanowires2017In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, no 3, article id 036804Article in journal (Refereed)
    Abstract [en]

    We calculate the charge current generated by a temperature bias between the two ends of a tubular nanowire. We show that in the presence of a transversal magnetic field the current can change sign; i.e., electrons can either flow from the hot to the cold reservoir, or in the opposite direction, when the temperature bias increases. This behavior occurs when the magnetic field is sufficiently strong, such that Landau and snaking states are created, and the energy dispersion is nonmonotonic with respect to the longitudinal wave vector. The sign reversal can survive in the presence of impurities. We predict this result for core-shell nanowires, for uniform nanowires with surface states due to the Fermi level pinning, and for topological insulator nanowires.

  • 8.
    Ferreiros, Yago
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Zyuzin, A. A.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Bardarson, Jens H
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Anomalous Nernst and thermal Hall effects in tilted Weyl semimetals2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 11, article id 115202Article in journal (Refereed)
    Abstract [en]

    We study the anomalous Nernst and thermal Hall effects in a linearized low-energy model of a tilted Weyl semimetal, with two Weyl nodes separated in momentum space. For inversion symmetric tilt, we give analytic expressions in two opposite limits: For a small tilt, corresponding to a type-I Weyl semimetal, the Nernst conductivity is finite and independent of the Fermi level; for a large tilt, corresponding to a type-II Weyl semimetal, it acquires a contribution depending logarithmically on the Fermi energy. This result is in a sharp contrast to the nontilted case, where the Nernst response is known to be zero in the linear model. The thermal Hall conductivity similarly acquires Fermi surface contributions, which add to the Fermi level-independent, zero-tilt result, and is suppressed as one over the tilt parameter at half filling in the type-II phase. In the case of inversion-breaking tilt, with the tilting vector of equal modulus in the two Weyl cones, all Fermi surface contributions to both anomalous responses cancel out, resulting in zero Nernst conductivity. We discuss two possible experimental setups, representing open and closed thermoelectric circuits.

  • 9.
    Javanmard, Younes
    et al.
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Trapin, Daniele
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Bera, Soumya
    Indian Inst Technol, Dept Phys, Bombay 400076, Maharashtra, India..
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory.
    Heyl, Markus
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Sharp entanglement thresholds in the logarithmic negativity of disjoint blocks in the transverse-field Ising chain2018In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 20, article id 083032Article in journal (Refereed)
    Abstract [en]

    Entanglement has developed into an essential concept for the characterization of phases and phase transitions in ground states of quantum many-body systems. In this work we use the logarithmic negativity to study the spatial entanglement structure in the transverse-field Ising chain both in the ground state and at nonzero temperatures. Specifically, we investigate the entanglement between two disjoint blocks as a function of their separation, which can be viewed as the entanglement analog of a spatial correlation function. We find sharp entanglement thresholds at a critical distance beyond which the logarithmic negativity vanishes exactly and thus the two blocks become unentangled, which holds even in the presence of long-ranged quantum correlations, i.e., at the system's quantum critical point. Using time-evolving block decimation, we explore this feature as a function of temperature and size of the two blocks and present a simple model to describe our numerical observations.

  • 10. Lezama, Talia L. M.
    et al.
    Bera, Soumya
    Schomerus, Henning
    Heidrich-Meisner, Fabian
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics. Max-Planck-Institut für Physik komplexer Systeme, Germany.
    One-particle density matrix occupation spectrum of many-body localized states after a global quench2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 6, article id 060202Article in journal (Refereed)
    Abstract [en]

    The emergent integrability of the many-body localized phase is naturally understood in terms of localized quasiparticles. As a result, the occupations of the one-particle density matrix in eigenstates show a Fermi-liquid-like discontinuity. Here, we show that in the steady state reached at long times after a global quench from a perfect density-wave state, this occupation discontinuity is absent, reminiscent of a Fermi liquid at a finite temperature, while the full occupation function remains strongly nonthermal. We discuss how one can understand this as a consequence of the local structure of the density-wave state and the resulting partial occupation of quasiparticles. This partial occupation can be controlled by tuning the initial state and can be described by an effective temperature.

  • 11.
    Rhim, Jun-Won
    et al.
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany.;Inst for Basic Sci Korea, Ctr Correlated Elect Syst, Seoul 08826, South Korea.;Seoul Natl Univ, Dept Phys & Astron, Seoul 08826, South Korea..
    Bardarson, Jens H.
    KTH, School of Engineering Sciences (SCI), Physics. Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Slager, Robert-Jan
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Unified bulk-boundary correspondence for band insulators2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 11, article id 115143Article in journal (Refereed)
    Abstract [en]

    The bulk-boundary correspondence, a topic of intensive research interest over the past decades, is one of the quintessential ideas in the physics of topological quantum matter. Nevertheless, it has not been proven in all generality and has in certain scenarios even been shown to fail, depending on the boundary profiles of the terminated system. Here, we introduce bulk numbers that capture the exact number of in-gap modes, without any such subtleties in one spatial dimension. Similarly, based on these 1D bulk numbers, we define a new 2D winding number, which we call the pole winding number, that specifies the number of robust metallic surface bands in the gap as well as their topological character. The underlying general methodology relies on a simple continuous extrapolation from the bulk to the boundary, while tracking the evolution of Green's function's poles in the vicinity of the bulk band edges. As a main result we find that all the obtained numbers can be applied to the known insulating phases in a unified manner regardless of the specific symmetries. Additionally, from a computational point of view, these numbers can be effectively evaluated without any gauge fixing problems. In particular, we directly apply our bulk-boundary correspondence construction to various systems, including 1D examples without a traditional bulk-boundary correspondence, and predict the existence of boundary modes on various experimentally studied graphene edges, such as open boundaries and grain boundaries. Finally, we sketch the 3D generalization of the pole winding number by in the context of topological insulators.

1 - 11 of 11
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf