Alexandrov and Bratkovsky Reply:

Comment on “Isotope effect in high-Tcsuperconductors”

“…As the result of poor screening the magnitude of an effective attraction between carriers, V ph ͑r͒ =−e 2 ͑⑀ ϱ −1 − ⑀ 0 −1 ͒ / r, induced by the Fröhlich EPI, 11 is essentially the same as the Coulomb repulsion, V c ͑r͒ = e 2 / ⑀ ϱ r, both on the order of 1 eV. Experimentally the strong Fröhlich EPI is validated by a huge difference in the static, ⑀ 0 ӷ 1, and high-frequency, ⑀ ϱ , dielectric constants of these ionic crystals, 27 ⑀ 0 ӷ ⑀ ϱ , by recent experimental observations of a c-axis lattice expansion in pump-probe experiments 29 and multiple-phonon peaks in the tunnelling spectra of superconducting cuprates, 30,31 as well as by a number of other observations including those mentioned earlier. 2,3,[5][6][7][8][9] Nevertheless the basic question concerning the key pairing interaction in cuprate and other high-temperature superconductors remains open.…”

“…27 EPI with c-axis-polarized optical phonons is virtually unscreened since the upper limit for the out-of-plane plasmon frequency 28 ͑Շ200 cm −1 ͒ is well below the characteristic frequency of optical phonons, Ϸ 400/ 1000 cm −1 in all cuprate superconductors. As the result of poor screening the magnitude of an effective attraction between carriers, V ph ͑r͒ =−e 2 ͑⑀ ϱ −1 − ⑀ 0 −1 ͒ / r, induced by the Fröhlich EPI, 11 is essentially the same as the Coulomb repulsion, V c ͑r͒ = e 2 / ⑀ ϱ r, both on the order of 1 eV.…”

Comment on “Origin of combination frequencies in quantum magnetic oscillations of two-dimensional multiband metals”

“…8 There are strong oscillations of a chemical potential pinned to the peaks in the Landau density of states in ͑quasi͒ 2D multiband metals, that cause this effect. 1 With the increase of the dimensionality 8 or background density of states, 2 the oscillations are strongly damped and the effect vanishes. Smallness of the chemical potential oscillations in 3D metals was already discussed by Dingle in 1951.…”

“…2 and 3 and observed experimentally by Shepherd et al 4 and by other groups. 5 We have also proposed an analytical theory 6 of the combination Fourier components in the framework of the semiclassical Lifshitz-Kosevich approach. 7 More recently the theory has been extended by taking into account the Dingle, spin and angle ͑Yamaji͒ reduction factors, and the nonquantized ''background'' density of states in quasi-2D multiband metals.…”

“…͑16͒, 6 for the magnetization amplitudes. The ratio of the combination M ␣␣ Ј 11 and single band ͑conventional͒ M ␣ 1 Fourier amplitudes in a two-band metal was found at Tϭ0 to be ͓Eq.…”