Raman Scattering versus Infrared Conductivity: Evidence for one-dimensional Conduction in La_{2-x}Sr_{x}CuO_{4}

Raman and Infrared (IR) spectra of an underdoped La_{1.90}Sr_{0.10}CuO_{4} single crystal have been measured as a function of temperature. Both techniques provide unconventional low-energy spectra. The IR conductivity exhibits features peaked at finite frequencies which do not have a counterpart in the Raman response. Below approximately 100 K a transfer of both Raman and IR spectral weight towards lower energies is found and a new component in the Raman response builds up being characterized by a very long lifetime of electrons propagating along the Cu-O bonds.Comment: 4 pages, 3 eps figure

Infrared signatures of charge stripes in La(2-x)Sr(x)CuO(4)

The in-plane optical conductivity of seven La(2-x)Sr(x)CuO(4) single crystals with x between 0 and 0.15 has been studied from 30 to 295 K. All doped samples exhibit strong peaks in the far-infrared, which closely resemble those observed in Cu-O "ladders" with one-dimensional charge-ordering. The behavior with doping and temperature of the peak energy, width, and intensity allows us to conclude that we are observing charge stripes dynamics in La(2-x)Sr(x)CuO(4) on the fast time scale of infrared spectroscopy.Comment: 9 pages including figs. in pdf forma

Effect of a Normal-State Pseudogap on Optical Conductivity in Underdoped Cuprate Superconductors

We calculate the c-axis infrared conductivity $\sigma_c(\omega)$ in underdoped cuprate superconductors for spinfluctuation exchange scattering within the CuO$_2$-planes including a phenomenological d-wave pseudogap of amplitude $E_g$. For temperatures decreasing below a temperature $T^* \sim E_g/2$, a gap for $\omega < 2E_g$ develops in $\sigma_c(\omega)$ in the incoherent (diffuse) transmission limit. The resistivity shows 'semiconducting' behavior, i.e. it increases for low temperatures above the constant behavior for $E_g=0$. We find that the pseudogap structure in the in-plane optical conductivity is about twice as big as in the interplane conductivity $\sigma_c(\omega)$, in qualitative agreement with experiment. This is a consequence of the fact that the spinfluctuation exchange interaction is suppressed at low frequencies as a result of the opening of the pseudogap. While the c-axis conductivity in the underdoped regime is described best by incoherent transmission, in the overdoped regime coherent conductance gives a better description.Comment: to be published in Phys. Rev. B (November 1, 1999

Physical therapy methods in the treatment and rehabilitation of cancer patients

The results of the effective use of magnetic laser therapy in the treatment and rehabilitation of cancer patients were presented. The effect of magnetic-laser therapy in the treatment of radiation-induced reactions in the patients with head and neck cancer and in the patients with breast cancer was analyzed. High efficiency of lymphedema and lymphorrhea treatment in the postoperative period in the patients with breast cancer was proved. The results of rehabilitation of the patients with gastric cancer after surgical treatment were presented. These data indicate a high effectiveness of different physical methods of treatment and rehabilitation of cancer patients

Anomalous optical absorption in overdoped cuprates near the charge-ordering instability

We propose an interpretation for the hump observed in the optical conductivity at or below a few hundreds of cm$^{-1}$, in overdoped cuprates like the electron-doped Nd_{2-x}Ce_xCuO_{4-y} at x\gtrsim 0.15 and the hole-doped Bi_2Sr_2CuO_6 and La_{2-x}Sr_xCuO_4. This interpretation is based on the direct excitation of charge collective modes, which become nearly critical in the proximity to a charge-ordering instability. The nearly critical character of these excitations entails a peculiar temperature dependence and a pseudo-scaling form of the lineshapes, which are in agreement with the experimental data.Comment: 5 pages, 3 figure

The pseudogap in high-temperature superconductors: an experimental survey

We present an experimental review of the nature of the pseudogap in the cuprate superconductors. Evidence from various experimental techniques points to a common phenomenology. The pseudogap is seen in all high temperature superconductors and there is general agreement on the temperature and doping range where it exists. It is also becoming clear that the superconducting gap emerges from the normal state pseudogap. The d-wave nature of the order parameter holds for both the superconducting gap and the pseudogap. Although an extensive body of evidence is reviewed, a consensus on the origin of the pseudogap is as lacking as it is for the mechanism underlying high temperature superconductivity.Comment: review article, 54 pages, 50 figure

What the resonance peak cannot do

In certain cuprates, a spin 1 resonance mode is prominent in the magnetic structure measured by neutron scattering. It has been proposed that this mode is responsible for significant features seen in other spectroscopies, such as photoemission and optical absorption, which are sensitive to the charge dynamics, and even that this mode is the boson responsibile for ``mediating'' the superconducting pairing. We show that its small (measured) intensity and weak coupling to electron-hole pairs (as deduced from the measured lifetime) disqualifies the resonant mode from either proposed role.Comment: 4 pages, no figur