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- Fogelström, Mikael, 1963, et al.
(författare)
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Nonlinear magnetic field dependence of the conductance in d-wave NIS tunnel junctions.
- 2004
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Ingår i: Physical Review B. ; 70:1, s. 012503-
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Tidskriftsartikel (refereegranskat)abstract
- The ab-plane normal-metal/insulator/superconductor-tunnelling conductance in d-wave superconductors shows a zero-bias conductance peak which is predicted to split in a magnetic field. In a pure d-wave superconductor the splitting is linear for fields small on the scale of the thermodynamic critical field. The field dependence is shown to be nonlinear, even at low fields, in the vicinity of a surface phase transition into a local time-reversal symmetry breaking state. The field evolution of the conductance is sensitive to temperature, doping, and the symmetry of the subdominant pairing channel.
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- Fogelström, Mikael, 1963, et al.
(författare)
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Two-channel point-contact tunneling theory of superconductors
- 2014
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 90:10, s. 104512-
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a two-channel tunneling model to generalize the widely used BTK theory of point-contact conductance between a normal metal contact and superconductor. Tunneling of electrons can occur via localized surface states or directly, resulting in a Fano resonance in the differential conductance G = d I /d V . We present an analysis of G within the two-channel model when applied to soft point contacts between normal metallic silver particles and prototypical heavy-fermion superconductors CeCoIn5 and CeRhIn5 at high pressures. In the normal state the Fano line shape of the measured G is well described by a model with two tunneling channels and a large temperature-independent background conductance. In the superconducting state a strongly suppressed Andreev reflection signal is explained by the presence of the background conductance. We report Andreev signal in CeCoIn5 consistent with standard dx2−y2 -wave pairing, assuming an equal mixture of tunneling into [100] and [110] crystallographic interfaces, whereas in CeRhIn5 at 1.8 and 2.0 GPa the signal is described by a dx2−y2 -wave gap with reduced nodal region, i.e., increased slope of the gap opening on the Fermi surface. A possibility is that the shape of the high-pressure Andreev signal is affected by the proximity of a line of quantum critical points that extends from 1.75 to 2.3 GPa, which is not accounted for in our description of the heavy-fermion superconductor.
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- Henriksson, Marielle, et al.
(författare)
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Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates
- 2011
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 71:1, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. in the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T-g, and this must be due to covalent matrix-nanofiber linkages.
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- Leppäkangas, Juha, 1979, et al.
(författare)
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Antibunched Photons from Inelastic Cooper-Pair Tunneling
- 2015
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 115:2
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate theoretically that charge transport across a Josephson junction, voltage-biased through a resistive environment, produces antibunched photons. We develop a continuous-mode description of the emitted radiation field in a semi-infinite transmission line terminated by the Josephson junction. Within a perturbative treatment in powers of the tunneling coupling across the Josephson junction, we capture effects originating in charging dynamics of consecutively tunneling Cooper pairs. We find that within a feasible experimental setup the Coulomb blockade provided by high zero-frequency impedance can be used to create antibunched photons at a very high rate and in a very versatile frequency window ranging from a few GHz to a THz.
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- Silaev, Mikhail A., et al.
(författare)
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Lifshitz Transition in the Double-Core Vortex in He-3-B
- 2015
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 115:23
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Tidskriftsartikel (refereegranskat)abstract
- We study the spectrum of fermion states localized within the vortex core of a weak-coupling p-wave superfluid. The low energy spectrum consists of two anomalous branches that generate a large density of states at the locations of the half cores of the vortex. Fermi liquid interactions significantly stretch the vortex structure, which leads to a Lifshitz transition in the effective Fermi surface of the vortex core fermions. We apply the results to the rotational dynamics of vortices in superfluid He-3-B and find an explanation for the observed slow mode.
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