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Thermofield dynamics: Quantum chaos versus decoherence ; Chenu, Aurélia ; et al in Physical Review. B, Condensed Matter and Materials Physics (2021) Quantum chaos imposes universal spectral signatures that govern the thermofield dynamics of a many-body system in isolation. The fidelity between the initial and time-evolving thermofield double states ... [more ▼] Quantum chaos imposes universal spectral signatures that govern the thermofield dynamics of a many-body system in isolation. The fidelity between the initial and time-evolving thermofield double states exhibits as a function of time a decay, dip, ramp, and plateau. Sources of decoherence give rise to a nonunitary evolution and result in information loss. Energy dephasing gradually suppresses quantum noise fluctuations and the dip associated with spectral correlations. Decoherence further delays the appearance of the dip and shortens the span of the linear ramp associated with chaotic behavior. The interplay between signatures of quantum chaos and information loss is determined by the competition among the decoherence, dip, and plateau characteristic times, as demonstrated in the stochastic Sachdev-Ye-Kitaev model. [less ▲] Detailed reference viewed: 53 (3 UL)Current correlations of Cooper-pair tunneling into a quantum Hall system Michelsen, Andreas Nicolai Bock ; Schmidt, Thomas ; Idrisov, Edvin in Physical Review. B, Condensed Matter and Materials Physics (2020), 102 Detailed reference viewed: 64 (4 UL)Quantum ammeter: Measuring full counting statistics of electron currents at quantum timescales Idrisov, Edvin ; ; in Physical Review. B, Condensed Matter and Materials Physics (2020), 101 Detailed reference viewed: 37 (1 UL)Transport properties of coupled Majorana bound states in the Coulomb blockade regime Ekström, Carl Johan Ingvar ; ; Schmidt, Thomas in Physical Review. B, Condensed Matter and Materials Physics (2020) Topologically protected qubits based on nanostructures hosting Majorana bound states (MBSs) hold great promise for fault-tolerant quantum computing. We study the transport properties of nanowire networks ... [more ▼] Topologically protected qubits based on nanostructures hosting Majorana bound states (MBSs) hold great promise for fault-tolerant quantum computing. We study the transport properties of nanowire networks hosting MBSs with a focus on the effects of the charging energy and the overlap between neighboring MBSs in short mesoscopic samples. In particular, we investigate structures hosting four MBSs such as T junctions and Majorana boxes. Using a master equation in the Markovian approximation, we discuss the leading transport processes mediated by the MBSs. Single-electron tunneling and processes involving creation and annihilation of Cooper pairs dominate in the sequential-tunneling limit. In the cotunneling regime the charge in the MBSs is fixed and transport is governed by transitions via virtual intermediate states. Our results show that four-terminal measurements in the T junction and Majorana box geometries can be useful tools for the characterization of the properties of MBSs with finite overlaps and charging energy. [less ▲] Detailed reference viewed: 92 (9 UL)Magnetic structure factor of correlated moments in small-angle neutron scattering Honecker, Dirk ; ; Bender, Philipp Florian in Physical Review. B, Condensed Matter and Materials Physics (2020), 101(13), 134401 The interplay between structural and magnetic properties of nanostructured magnetic materials allows one to realize unconventional magnetic effects, which results in a demand for experimental techniques ... [more ▼] The interplay between structural and magnetic properties of nanostructured magnetic materials allows one to realize unconventional magnetic effects, which results in a demand for experimental techniques to determine the magnetization profile with nanoscale resolution. Magnetic small-angle neutron scattering (SANS) probes both the chemical and magnetic nanostructure and is thus a powerful technique, e.g., for the characterization of magnetic nanoparticles. Here, we show that the conventionally used particle-matrix approach to describe SANS of magnetic particle assemblies, however, leads to a flawed interpretation. As a remedy, we provide general expressions for the field-dependent two-dimensional magnetic SANS cross section of correlated moments. It is shown that for structurally disordered ensembles the magnetic structure factor is in general, and contrary to common assumptions, (i) anisotropic also in zero field and (ii) that even in saturation the magnetic structure factor deviates from the nuclear one. These theoretical predictions explain qualitatively the intriguing experimental, polarized SANS data of an ensemble of dipolar-coupled iron oxide nanoparticles. [less ▲] Detailed reference viewed: 118 (2 UL)Fluctuational electrodynamics in atomic and macroscopic systems: van derWaals interactions and radiative heat transfer ; ; Tkatchenko, Alexandre et al in Physical Review. B, Condensed Matter and Materials Physics (2020) Detailed reference viewed: 113 (2 UL)Experimental observation of third-order effect in magnetic small-angle neutron scattering ; ; Honecker, Dirk et al in Physical Review. B, Condensed Matter and Materials Physics (2020), 101 Detailed reference viewed: 68 (1 UL)Parafermion braiding in fractional quantum Hall edge states with a finite chemical potential Groenendijk, Solofo ; ; et al in Physical Review. B, Condensed Matter and Materials Physics (2019), 100 Parafermions are non-Abelian anyons which generalize Majorana fermions and hold great promise for topological quantum computation. We study the braiding of Z2n parafermions which have been predicted to ... [more ▼] Parafermions are non-Abelian anyons which generalize Majorana fermions and hold great promise for topological quantum computation. We study the braiding of Z2n parafermions which have been predicted to emerge as localized zero modes in fractional quantum Hall systems at filling factor ν=1/n (n odd). Using a combination of bosonization and refermionization, we calculate the energy splitting as a function of distance and chemical potential for a pair of parafermions separated by a gapped region. Braiding of parafermions in quantum Hall edge states can be implemented by repeated fusion and nucleation of parafermion pairs. We simulate the conventional braiding protocol of parafermions numerically, taking into account the finite separation and finite chemical potential. We show that a nonzero chemical potential poses challenges for the adiabaticity of the braiding process because it leads to accidental crossings in the spectrum. To remedy this, we propose an improved braiding protocol which avoids those degeneracies. [less ▲] Detailed reference viewed: 95 (2 UL)Evidence for the formation of nanoprecipitates with magnetically disordered regions in bulk Ni50Mn45In5 Heusler alloys ; Titov, Ivan ; Malyeyev, Artem et al in Physical Review. B, Condensed Matter and Materials Physics (2019), 99 Detailed reference viewed: 199 (24 UL)Critical size limits for collinear and spin-spiral magnetism in $CoCr_2\mathrmO_4$ ; ; et al in Physical Review. B, Condensed Matter and Materials Physics (2019), 100 The multiferroic behavior of CoCr2O4 results from the appearance of conical spin-spiral magnetic ordering, which induces electric polarization. The magnetic ground state has a complex size-dependent ... [more ▼] The multiferroic behavior of CoCr2O4 results from the appearance of conical spin-spiral magnetic ordering, which induces electric polarization. The magnetic ground state has a complex size-dependent behavior, which collapses when reaching a critical particle size. Here the magnetic phase stability of CoCr2O4 in the size range of 3.6–14.0 nm is presented in detail using the combination of neutron diffraction with XYZ polarization analysis and macroscopic magnetization measurements. We establish critical coherent domain sizes for the formation of the spin spiral and ferrimagnetic structure and reveal the evolution of the incommensurate spin spiral vector with particle size. We further confirm the presence of ferroelectric polarization in the spin spiral phase for nanocrystalline CoCr2O4. [less ▲] Detailed reference viewed: 84 (11 UL)Erratum: Third-order effect in magnetic small-angle neutron scattering by a spatially inhomogeneous medium [Phys. Rev. B 91, 054404 (2015)] ; Michels, Andreas in Physical Review. B, Condensed Matter and Materials Physics (2019), 99 Detailed reference viewed: 110 (0 UL)Unconventional superconductivity in the extended Hubbard model: Weak-coupling renormalization group ; Schmidt, Thomas ; in Physical Review. B, Condensed Matter and Materials Physics (2018) Detailed reference viewed: 150 (0 UL)Charge and energy fractionalization mechanism in one-dimensional channels ; Calzona, Alessio ; Dolcetto, Giacomo et al in Physical Review. B, Condensed Matter and Materials Physics (2017), 96 We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to ... [more ▼] We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to charge and energy fractionalization. We elucidate this concept by calculating the nonequilibrium electron distribution function in the momentum and energy domains after the injection of an energy-resolved electron. Our results shed light on how fractionalization occurs via the creation of particle-hole pairs by the injected electron. In particular, we focus on systems with a pair of counterpropagating channels, and we fully analyze the properties of each chiral fractional excitation which is created by the injection. We suggest possible routes to access their energy and momentum distribution functions in topological quantum Hall or quantum spin-Hall edge states. [less ▲] Detailed reference viewed: 235 (10 UL)Spin-orbit coupling in quasi-one-dimensional Wigner crystals ; Pedder, Christopher ; Schmidt, Thomas in Physical Review. B, Condensed Matter and Materials Physics (2017), 95(4), 045413 We study the effect of Rashba spin-orbit coupling (SOC) on the charge and spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal. As electrons in a quasi-1D Wigner crystal can move ... [more ▼] We study the effect of Rashba spin-orbit coupling (SOC) on the charge and spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal. As electrons in a quasi-1D Wigner crystal can move in the transverse direction, SOC cannot be gauged away in contrast to the pure 1D case. We show that for weak SOC, a partial gap in the spectrum opens at certain ratios between density of electrons and the inverse Rashba length. We present how the low-energy branch of charge degrees of freedom deviates due to SOC from its usual linear dependence at small wave vectors. In the case of strong SOC, we show that spin sector of a Wigner crystal cannot be described by an isotropic antiferromagnetic Heisenberg Hamiltonian any more, and that instead the ground state of neighboring electrons is mostly a triplet state. We present a new spin sector Hamiltonian and discuss the spectrum of Wigner crystal in this limit. [less ▲] Detailed reference viewed: 299 (11 UL)Time-resolved energy dynamics after single electron injection into an interacting helical liquid Calzona, Alessio ; ; et al in Physical Review. B, Condensed Matter and Materials Physics (2016), 94(03), 5404 The possibility of injecting a single electron into ballistic conductors is at the basis of the new field of electron quantum optics. Here, we consider a single electron injection into the helical edge ... [more ▼] The possibility of injecting a single electron into ballistic conductors is at the basis of the new field of electron quantum optics. Here, we consider a single electron injection into the helical edge channels of a topological insulator. Their counterpropagating nature and the unavoidable presence of electron-electron interactions dramatically affect the time evolution of the single wave packet. Modeling the injection process from a mesoscopic capacitor in the presence of nonlocal tunneling, we focus on the time-resolved charge and energy packet dynamics. Both quantities split up into counterpropagating contributions whose profiles are strongly affected by the interaction strength. In addition, stronger signatures are found for the injected energy, which is also affected by the finite width of the tunneling region, in contrast to what happens for the charge. Indeed, the energy flow can be controlled by tuning the injection parameters, and we demonstrate that, in the presence of nonlocal tunneling, it is possible to achieve a situation in which charge and energy flow in opposite directions. [less ▲] Detailed reference viewed: 86 (6 UL)Stability of a spin-triplet nematic state near to a quantum critical point ; Pedder, Christopher ; et al in Physical Review. B, Condensed Matter and Materials Physics (2016), 93(23), 5105 We analyze a model of itinerant electrons interacting through a quadrupole density-density repulsion in three dimensions. At the mean field level, the interaction drives a continuous Pomeranchuk ... [more ▼] We analyze a model of itinerant electrons interacting through a quadrupole density-density repulsion in three dimensions. At the mean field level, the interaction drives a continuous Pomeranchuk instability towards d-wave, spin-triplet nematic order, which simultaneously breaks the SU(2) spin-rotation and spatial rotational symmetries. This order results in spin antisymmetric, elliptical deformations of the Fermi surfaces of up and down spins. We show that the effects of quantum fluctuations are similar to those in metallic ferromagnets, rendering the nematic transition first-order at low temperatures. Using the fermionic quantum order-by-disorder approach to self-consistently calculate fluctuations around possible modulated states, we show that the first-order transition is pre-empted by the formation of a nematic state that is intertwined with a helical modulation in spin space. Such a state is closely related to d-wave bond density wave order in square-lattice systems. Moreover, we show that it may coexist with a modulated, p-wave superconducting state. [less ▲] Detailed reference viewed: 172 (10 UL)Phonon-limited carrier mobility and resistivity from carbon nanotubes to graphene ; Pereira Coutada Miranda, Henrique ; et al in Physical Review. B, Condensed Matter and Materials Physics (2015) Under which conditions do the electrical transport properties of one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent? We have performed atomistic calculations of the phonon ... [more ▼] Under which conditions do the electrical transport properties of one-dimensional (1D) carbon nanotubes (CNTs) and 2D graphene become equivalent? We have performed atomistic calculations of the phonon-limited electrical mobility in graphene and in a wide range of CNTs of different types to address this issue. The theoretical study is based on a tight-binding method and a force-constant model from which all possible electron-phonon couplings are computed. The electrical resistivity of graphene is found in very good agreement with experiments performed at high carrier density. A common methodology is applied to study the transition from one to two dimensions by considering CNTs with diameter up to 16 nm. It is found that the mobility in CNTs of increasing diameter converges to the same value, i.e., the mobility in graphene. This convergence is much faster at high temperature and high carrier density. For small-diameter CNTs, the mobility depends strongly on chirality, diameter, and the existence of a band gap. [less ▲] Detailed reference viewed: 295 (11 UL)Third-order effect in magnetic small-angle neutron scattering by a spatially inhomogeneous medium ; Michels, Andreas in Physical Review. B, Condensed Matter and Materials Physics (2015), 91 Detailed reference viewed: 170 (11 UL)Ab initio perspective on the Mollwo-Ivey relation for F centers in alkali halides ; ; et al in Physical Review. B, Condensed Matter and Materials Physics (2015), 92 We revisit the well-known Mollwo-Ivey relation that describes the ``universal'' dependence of the absorption energies of F-type color centers on the lattice constant a of alkali-halide crystals, E-abs ... [more ▼] We revisit the well-known Mollwo-Ivey relation that describes the ``universal'' dependence of the absorption energies of F-type color centers on the lattice constant a of alkali-halide crystals, E-abs proportional to a(-n). We perform both state-of-the-art ab initio quantum chemistry and post-DFT calculations of F-center absorption spectra. By ``tuning'' independently the lattice constant and the atomic species we show that the scaling with the lattice constant alone 2 in agreement with the ``particle-in-the-box'' model. Keeping the lattice constant fixed and changing the atomic species enables us to quantify the ion-size effects which are shown to be responsible for the exponent n approximate to 1.8. [less ▲] Detailed reference viewed: 101 (3 UL)Nature of heat in strongly coupled open quantum systems Esposito, Massimiliano ; ; in Physical Review. B, Condensed Matter and Materials Physics (2015), 92(23), We show that any heat definition expressed as an energy change in the reservoir energy plus any fraction of the system-reservoir interaction is not an exact differential when evaluated along reversible ... [more ▼] We show that any heat definition expressed as an energy change in the reservoir energy plus any fraction of the system-reservoir interaction is not an exact differential when evaluated along reversible isothermal transformations, except when that fraction is zero. Even in that latter case the reversible heat divided by temperature, namely entropy, does not satisfy the third law of thermodynamics and diverges in the low temperature limit. These results are found within the framework of nonequilibrium Green functions (NEGF) using a single level quantum dot strongly coupled to fermionic reservoirs and subjected to a time-dependent protocol modulating the dot energy as well as the dot-reservoir coupling strength. © 2015 American Physical Society. [less ▲] Detailed reference viewed: 170 (6 UL) |
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