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Results 1-20 of 80.
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Disorder-driven exceptional lines and Fermi ribbons in tilted nodal-line semimetals ; ; et al in Physical Review. B, Condensed Matter (2019), 99 We consider the impact of disorder on the spectrum of three-dimensional nodal-line semimetals. We show that the combination of disorder and a tilted spectrum naturally leads to a non-Hermitian self-energy ... [more ▼] We consider the impact of disorder on the spectrum of three-dimensional nodal-line semimetals. We show that the combination of disorder and a tilted spectrum naturally leads to a non-Hermitian self-energy contribution that can split a nodal line into a pair of exceptional lines. These exceptional lines form the boundary of an open and orientable bulk Fermi ribbon in reciprocal space on which the energy gap vanishes. We find that the orientation and shape of such a disorder-induced bulk Fermi ribbon is controlled by the tilt direction and the disorder properties, which can also be exploited to realize a twisted bulk Fermi ribbon with nontrivial winding number. Our results put forward a paradigm for the exploration of non-Hermitian topological phases of matter. [less ▲] Detailed reference viewed: 62 (10 UL)Z4 parafermions in one-dimensional fermionic lattices Calzona, Alessio ; ; et al in Physical Review. B, Condensed Matter (2018), 98 Parafermions are emergent excitations which generalize Majorana fermions and are potentially relevant to topological quantum computation. Using the concept of Fock parafermions, we present a mapping ... [more ▼] Parafermions are emergent excitations which generalize Majorana fermions and are potentially relevant to topological quantum computation. Using the concept of Fock parafermions, we present a mapping between lattice Z4-parafermions and lattice spin-1/2 fermions which preserves the locality of operators with Z4 symmetry. Based on this mapping, we construct an exactly solvable, local one-dimensional fermionic Hamiltonian which hosts parafermionic edge states. We numerically show that the parafermionic phase remains stable in a wide range of parameters, and discuss its signatures in the fermionic spectral function. [less ▲] Detailed reference viewed: 38 (1 UL)Fundamental limits to helical edge conductivity due to sphin-phonon scattering Groenendijk, Solofo ; ; Schmidt, Thomas in Physical Review. B, Condensed Matter (2018), 97 Detailed reference viewed: 50 (6 UL)Universal scaling of quench-induced correlations in a one-dimensional channel at finite temperature Calzona, Alessio ; ; et al in SciPost Physics (2018) It has been shown that a quantum quench of interactions in a one-dimensional fermion system at zero temperature induces a universal power law ∝t−2 in its long-time dynamics. In this paper we demonstrate ... [more ▼] It has been shown that a quantum quench of interactions in a one-dimensional fermion system at zero temperature induces a universal power law ∝t−2 in its long-time dynamics. In this paper we demonstrate that this behaviour is robust even in the presence of thermal effects. The system is initially prepared in a thermal state, then at a given time the bath is disconnected and the interaction strength is suddenly quenched. The corresponding effects on the long times dynamics of the non-equilibrium fermionic spectral function are considered. We show that the non-universal power laws, present at zero temperature, acquire an exponential decay due to thermal effects and are washed out at long times, while the universal behaviour ∝t−2 is always present. To verify our findings, we argue that these features are also visible in transport properties at finite temperature. The long-time dynamics of the current injected from a biased probe exhibits the same universal power law relaxation, in sharp contrast with the non-quenched case which features a fast exponential decay of the current towards its steady value, and thus represents a fingerprint of quench-induced dynamics. Finally, we show that a proper tuning of the probe temperature, compared to that of the one-dimensional channel, can enhance the visibility of the universal power-law behaviour. [less ▲] Detailed reference viewed: 57 (0 UL)Quantum thermodynamics of the resonant-level model with driven system-bath coupling ; Esposito, Massimiliano ; Schmidt, Thomas in Physical Review. B, Condensed Matter (2018), 97 Detailed reference viewed: 55 (9 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: 68 (0 UL)Magnetotransport signatures of three-dimensional topological insulator nanostructures Moors, Kristof ; ; et al in Physical Review. B (2018), 97(24), 245429 We study the magnetotransport properties of patterned 3D topological insulator nanostructures with several leads, such as kinks or Y-junctions, near the Dirac point with analytical as well as numerical ... [more ▼] We study the magnetotransport properties of patterned 3D topological insulator nanostructures with several leads, such as kinks or Y-junctions, near the Dirac point with analytical as well as numerical techniques. The interplay of the nanostructure geometry, the external magnetic field, and the spin-momentum locking of the topological surface states lead to a richer magnetoconductance phenomenology as compared to straight nanowires. Similar to straight wires, a quantized conductance with perfect transmission across the nanostructure can be realized across a kink when the input and output channels are pierced by a half-integer magnetic flux quantum. Unlike for straight wires, there is an additional requirement depending on the orientation of the external magnetic field. A right-angle kink shows a unique π -periodic magnetoconductance signature as a function of the in-plane angle of the magnetic field. For a Y-junction, the transmission can be perfectly steered to either of the two possible output legs by a proper alignment of the external magnetic field. These magnetotransport signatures offer new ways to explore topological surface states and could be relevant for quantum transport experiments on nanostructures which can be realized with existing fabrication methods. [less ▲] Detailed reference viewed: 46 (6 UL)Quantum thermodynamics of the resonant-level model with driven system-bath coupling Schmidt, Thomas ; Esposito, Massimiliano ; Haughian, Patrick E-print/Working paper (2017) Detailed reference viewed: 88 (7 UL)Fermionic reaction coordinates and their application to an autonomous Maxwell demon in the strong coupling regime Strasberg, Philipp ; ; Schmidt, Thomas et al E-print/Working paper (2017) Detailed reference viewed: 66 (1 UL)Energy and momentum distribution of fractional excitations in helical systems Calzona, Alessio ; ; Dolcetto, Giacomo et al Poster (2017, September 05) Detailed reference viewed: 30 (1 UL)Charge and energy fractionalization mechanism in one-dimensional channels ; Calzona, Alessio ; Dolcetto, Giacomo et al in Physical Review B (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: 79 (6 UL)Energy and momentum distribution of fractional excitations in 1D counterpropagating systems Calzona, Alessio ; ; Dolcetto, Giacomo et al Poster (2017, July 25) Detailed reference viewed: 18 (1 UL)Charge pumping through a polaron quantum dot Haughian, Patrick ; ; et al Poster (2017, July) Nanoelectromechanical systems exhibit a rich phenomenology due to the interaction of electronic and mechanical degrees of freedom. If this interaction is sufficiently strong, it leads to drastic ... [more ▼] Nanoelectromechanical systems exhibit a rich phenomenology due to the interaction of electronic and mechanical degrees of freedom. If this interaction is sufficiently strong, it leads to drastic suppression of conductance ("Franck-Condon blockade''). We show that this blockade can be exponentially lifted by application of an AC voltage. Multi-parameter drive protocols generate a pump current which enjoys the same enhancement. [less ▲] Detailed reference viewed: 37 (0 UL)Missing shapiro steps and the 8PI-periodic Josephson effect in the interacting helical electron systems Pedder, Christopher ; ; et al in Physica B: Condensed Matter (2017) Detailed reference viewed: 21 (1 UL)Charge and energy fractionalization mechanism in one-dimenional chanels ; Calzona, Alessio ; Dolcetto, Giacomo et al in Physical Review. B : Condensed Matter (2017) Detailed reference viewed: 31 (0 UL)Spin-orbit coupling in quasi-one-dimensional Wigner crystals ; Pedder, Christopher ; Schmidt, Thomas in Physical Review B (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: 100 (8 UL)Dynamic response functions and helical gaps in interacting Rashba nanowires with and without magnetic fields Pedder, Christopher ; ; et al in Physical Review B (2016), 94(24), 245414 A partially gapped spectrum due to the application of a magnetic field is one of the main probes of Rashba spin-orbit coupling in nanowires. Such a ``helical gap'' manifests itself in the linear ... [more ▼] A partially gapped spectrum due to the application of a magnetic field is one of the main probes of Rashba spin-orbit coupling in nanowires. Such a ``helical gap'' manifests itself in the linear conductance, as well as in dynamic response functions such as the spectral function, the structure factor, or the tunnelling density of states. In this paper, we investigate theoretically the signature of the helical gap in these observables with a particular focus on the interplay between Rashba spin-orbit coupling and electron-electron interactions. We show that in a quasi-one-dimensional wire, interactions can open a helical gap even without magnetic field. We calculate the dynamic response functions using bosonization, a renormalization group analysis, and the exact form factors of the emerging sine-Gordon model. For special interaction strengths, we verify our results by refermionization. We show how the two types of helical gaps, caused by magnetic fields or interactions, can be distinguished in experiments. [less ▲] Detailed reference viewed: 95 (21 UL)Lifting the Franck-Condon blockade in driven quantum dots Haughian, Patrick ; ; et al in Physical Review. B : Condensed Matter (2016), 94 Electron-vibron coupling in quantum dots can lead to a strong suppression of the average current in the sequential tunneling regime. This effect is known as Franck-Condon blockade and can be traced back ... [more ▼] Electron-vibron coupling in quantum dots can lead to a strong suppression of the average current in the sequential tunneling regime. This effect is known as Franck-Condon blockade and can be traced back to an overlap integral between vibron states with different electron numbers which becomes exponentially small for large electron-vibron coupling strength. Here, we investigate the effect of a time-dependent drive on this phenomenon, in particular the effect of an oscillatory gate voltage acting on the electronic dot level. We employ two different approaches: perturbation theory based on nonequilibrium Keldysh Green's functions and a master equation in Born-Markov approximation. In both cases, we find that the drive can lift the blockade by exciting vibrons. As a consequence, the relative change in average current grows exponentially with the drive strength. [less ▲] Detailed reference viewed: 73 (12 UL)Spin-orbit coupling in quasi-one dimensional Wigner crystals Kornich, Viktoriia ; Pedder, Christopher ; Schmidt, Thomas in Physical Review. B: Condensed Matter and Materials Physics (2016) Detailed reference viewed: 34 (0 UL)Helical gaps in interacting Rashba wires Schmidt, Thomas Scientific Conference (2016, September) Detailed reference viewed: 20 (2 UL) |
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