101,950 research outputs found
Comment on "Spin dynamics of the electron-doped high-T(c) superconducting cuprates"
No full textDahm T, Eremin I. Comment on "Spin dynamics of the electron-doped high-T(c) superconducting cuprates". Physical Review Letters. 2006;97(23): 239701
Anisotropy of the quasiparticle damping in the high-T-c superconductors Bi2Sr2CaCu2O8 and YBa2Cu3O6.9 as seen from angle-resolved photoemission experiments
No full textDahm T. Anisotropy of the quasiparticle damping in the high-T-c superconductors Bi2Sr2CaCu2O8 and YBa2Cu3O6.9 as seen from angle-resolved photoemission experiments. PHYSICAL REVIEW B. 1996;54(14):10150-10154.Angle-resolved photoemission experiments have shown that the quasiparticle damping in the normal state of YBa2Cu3O6.9 is quite anisotropic while in Bi2Sr2CaCu2O8 it is only slightly anisotropic. However, both possess Fermi surfaces which are similar in shape, Here I show that the anisotropy of the damping can be understood within a simple picture, if one assumes a momentum-dependent interaction of the spin fluctuation exchange type and takes into account the Fermi surfaces of Bi2Sr2CaCu2O8 and YBa2Cu3O6.9
Theory of microwave intermodulation in a high-T-c superconducting microstrip resonator
No full textDahm T, Scalapino DJ. Theory of microwave intermodulation in a high-T-c superconducting microstrip resonator. Applied Physics Letters. 1996;69(27):4248-4250.We calculate the intermodulation power for a superconducting microstrip resonator arising from the intrinsic microscopic nonlinearities. We focus on high-T-c superconductors where it is believed that the order parameter has d(x2-y2) symmetry. A characteristic upturn of the intermodulation power is found at low temperatures. We discuss different ways to reduce intermodulations by changing the geometry of the microstrip. (C) 1996 American Institute of Physics
Intermodulation and quality factor of high-T-c superconducting microstrip structures
No full textDahm T, Scalapino DJ. Intermodulation and quality factor of high-T-c superconducting microstrip structures. Journal of Applied Physics. 1997;82(1):464-468.The intermodulation power and quality factor Q of high-T-c superconducting microstrip resonators with different shapes is calculated. Acute corners increase the losses and the intermodulation power. The influence of normal conducting regions is investigated. The case of two microstrips carrying in phase or out of phase currents is also studied. The losses and the intermodulation power are significantly reduced if the currents are in phase in the two microstrips compared to the mode with out of phase currents. (C) 1997 American Institute of Physics
Dependence of T-c on the q-omega structure of the spin-fluctuation spectrum
No full textDahm T, Scalapino DJ. Dependence of T-c on the q-omega structure of the spin-fluctuation spectrum. PHYSICAL REVIEW B. 2018;97(18): 4.A phenomenological spin-fluctuation analysis [Dahm et al., Nat. Phys. 5, 217 (2009)], based upon inelastic neutron scattering (INS) and angular resolved photoemission spectroscopy (ARPES) data for YBCO6.6 (T-c = 61 K), is used to calculate the functional derivative of the d-wave eigenvalue lambda(d) of the linearized gap equation with respect to the imaginary part of the spin susceptibility. chi '' (q,omega) at 70K. For temperatures near T-c, the variation of T-c with respect to. chi '' (q,omega) is proportional to this functional derivative. We find that above an energy similar to 4T(c) the functional derivative becomes positive so that adding spin-fluctuation spectral weight at higher frequencies leads to an increase in T-c. The strongest pairing occurs for large momentum transfers, and small momentum spin-fluctuations suppress the pairing
Dyke emplacement in fractured media: application to the 2000 intrusion at Izu islands, Japan
No full textWe use a boundary element approach to study the problem of a large, magma-filled dyke embedded in a fractured, damaged medium. The numerical simulations show that the dyke opening and the crack extension force at the dyke tip increases with increasing fracture density. We show that this behaviour can at moderate fracture densities be predicted by an effective media model. Simple analytical formulae are given for the increasing average opening of the dyke and the decreasing fracture toughness as functions of increasing fracture density. The numerical and the theoretical results are found to be in good agreement. In a first application we tested the model by using GPS deformation and seismicity data from a recent lateral magma intrusion in Izu islands, Japan. This shows that a simple comparison of the distance change and the cumulative earthquake number enables the study of the stability of the dyke intrusion. The method seems to distinguish whether the dyke opening is actively driven by magma influx or passively driven by an expansion due to fracturing
Verursachen magnetische Anregungen Hochtemperatur-Supraleitung?
No full textDahm T. Verursachen magnetische Anregungen Hochtemperatur-Supraleitung? Physik in unserer Zeit. 2009;40
Indication for an antiferromagnetic exchange interaction in high-T-c superconductors
No full textDahm T. Indication for an antiferromagnetic exchange interaction in high-T-c superconductors. PHYSICAL REVIEW B. 1996;53(21):14051-14054.Recently observed dip structures in angle-resolved photoemission spectroscopy and electron-tunneling experiments on high-T-c superconductors are investigated choosing an antiferromagnetic exchange interaction with a resonant peak structure in frequency as observed in recent neutron-scattering experiments. In our calculations we see similar structures in the spectral weight, in the density of states, and in the c-axis optical conductivity, which provides a possible explanation for this unusual behavior
Isotope effect in the presence of a pseudogap
No full textDahm T. Isotope effect in the presence of a pseudogap. Physical Review B. 2000;61(9):6381-6386.We investigate the question of whether the unusual doping dependence of the isotope exponent observed in underdoped high-T-c superconductors might be related to another unusual phenomenon observed in these systems: the pseudogap phenomenon. Within different approximations we study the influence of a phenomenological pseudogap on the isotope exponent and fmd that it generally strongly increases the isotope exponent, in qualitative agreement with experiments on underdoped high-T-c compounds. This result is stable against strong-coupling self-energy corrections and also holds for recently proposed spin-fluctuation exchange models, if a weak additional electron-phonon coupling is considered
Magnetically robust topological edge states and flat bands
No full textPaananen T, Dahm T. Magnetically robust topological edge states and flat bands. Phys. Rev. B. 2013;87(19): 195447
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