Ortolani, M., Dore, P., Di Castro, D., Perucchi, A., Lupi, S., Ferrando, V., ...
The optical response of the two-band superconductor MgB$_2$ has been studied in the 0.7-4 THz range on films with very low impurity level. The effect of the high-energy $\sigma$-gap is observed in...
Pressure dependence of the optical properties of the charge-density-wave compound LaTe$_2$ (2007)
Lavagnini, M., Sacchetti, A., Degiorgi, L., Arcangeletti, E., Baldassarre, L., Postorino, P., ...
We report the pressure dependence of the optical response of LaTe$_2$, which is deep in the charge-density-wave (CDW) ground state even at 300 K. The reflectivity spectrum is collected in the...
Sub-THz electrodynamics of the graphene-like superconductor CaAlSi (2007)
Lupi, S., Baldassarre, L., Ortolani, M., Mirri, C., Schade, U., Sopracase, R., ...
We report the first optical study of CaAlSi, a superconductor which displays both the crystal structure of MgB2 and the electronic band structure of intercalated graphites. The reflectivity of a...
Quasiparticle evolution and pseudogap formation in V2O3: An infrared spectroscopy study (2007)
Baldassarre, L., Perucchi, A., Nicoletti, D., Toschi, A., Sangiovanni, G., Held, K., ...
The infrared conductivity of V2O3 is measured in the whole phase diagram. Quasiparticles appear above the Neel temperature TN and eventually disappear further enhancing the temperature, leading to a...
Electrodynamics near the Metal-to-Insulator Transition in V3O5 (2007)
Baldassarre, L., Perucchi, A., Arcangeletti, E., Nicoletti, D., Di Castro, D., Postorino, P., ...
The electrodynamics near the metal-to-insulator transitions (MIT) induced, in V3O5 single crystals, by both temperature (T) and pressure (P) has been studied by infrared spectroscopy. The T- and...
Evidence of a pressure-induced metallization process in monoclinic VO$_2$ (2006)
Arcangeletti, E., Baldassarre, L., Di Castro, D., Lupi, S., Malavasi, L., Marini, C., ...
Raman and combined trasmission and reflectivity mid infrared measurements have been carried out on monoclinic VO$_2$ at room temperature over the 0-19 GPa and 0-14 GPa pressure ranges, respectively....
Pressure dependence of the charge-density-wave gap in rare-earth tri-tellurides (2006)
Sacchetti, A., Arcangeletti, E., Perucchi, A., Baldassarre, L., Postorino, P., Lupi, S., ...
We investigate the pressure dependence of the optical properties of CeTe$_3$, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the...
Low-energy electrodynamics of superconducting diamond (2006)
Ortolani, M., Lupi, S., Baldassarre, L., Calvani, P., Schade, U., Takano, Y., ...
Heavily-boron-doped diamond films become superconducting with critical temperatures $T_c$ well above 4 K. Here we first measure the reflectivity of such a film down to 5 cm$^{-1}$, by also using...
Infrared observation of the Hund's mechanism in an electron-doped manganite (2006)
Nucara, A., Calvani, P., Crispoldi, F., Sali, D., Lupi, S., Martin, C., ...
In the mid-infrared absorption of Sr{1-x}Ce{x}MnO{3} at low electron doping (x = 0.05), a band at 0.3 eV is fully replaced by another one at 0.9 eV as the system becomes antiferromagnetic (AF) of...
Ortolani, M., Calvani, P., Lupi, S., Schade, U., Perla, A., Fujita, M., ...
The reflectivity $R (\omega)$ of both the $ab$ plane and the c axis of two single crystals of La$_{1.875}$Ba$_{0.125-y}$Sr$_{y}$CuO$_4$ has been measured down to 5 cm$^{-1}$, using coherent...
Toschi, A., Capone, M., Ortolani, M., Calvani, P., Lupi, S., Castellani, C.
We compare calculations based on the Dynamical Mean-Field Theory of the Hubbard model with the infrared spectral weight $W(\Omega,T)$ of La$_{2-x}$Sr$_x$CuO$_4$ and other cuprates. Without using...
Infrared Conductivity and Charge Ordering in NaCoO2 (2005)
Lupi, S., Ortolani, M., Baldassarre, L., Calvani, P., Prabhakaran, D., Boothroyd, A. T.
The infrared conductivity of NaxCoO2 is studied as a function of doping and temperature for x between 0.5 and 1. Charge localization in CoO2 layers shows up through a far-infrared peak (FIP) in the...
Ortolani, M., Calvani, P., Lupi, S.
By using new and previous measurements of the $ab$-plane conductivity $\sigma_1^{ab} (\omega,T)$ of La$_{2-x}$Sr$_x$CuO$_{4}$ (LSCO) it is shown that the spectral weight $W = \int_0^\Omega...
Ortolani, M., Calvani, P., Lupi, S., Maselli, P., Fujita, M., Yamada, K.
Most of the novel superconductors are uniaxial crystals, with metallic planes ($ab$) orthogonal to an insulating axis ($c$). Far-infrared measurements of the reflectivity $R_{ab} (\omega)$ provide...
The infrared spectrum of Na_0.57CoO_2 (2003)
Lupi, S., Ortolani, M., Calvani, P.
The optical conductivity of single crystals of Na_xCoO_2 for $x$ = 0.57 is first reported between 295 and 30 K. In the far infrared, an "anomalous Drude" analysis leads to a carrier effective mass of...
Lucarelli et al. reply to Tajima et al. (cond-mat 0303493) (2003)
Lucarelli, A., Lupi, S., Ortolani, M., Calvani, P., Maselli, P., Capizzi, M.
In their Comment to a recent paper of ours [Lucarelli et al., PRL 92, 037002 (2003)], Tajima et al. (cond-mat 0303493) argue that the samples of La(2-x)Sr(x)CuO(4) where we find far-infrared peaks...
Venturini, F., Zhang, Q. -M., Hackl, R., Lucarelli, A., Lupi, S., Ortolani, M., ...
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....
Infrared signatures of charge stripes in La(2-x)Sr(x)CuO(4) (2002)
Lucarelli, A., Lupi, S., Ortolani, M., Calvani, P., Maselli, P., Capizzi, M., ...
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,...
Optical conductivity of the nonsuperconducting cuprate La(8-x)Sr(x)Cu(8)O(20) (2001)
Lucarelli, A., Lupi, S., Calvani, P., Maselli, P., De Marzi, G., Roy, P., ...
La(8-x)Sr(x)Cu(8)O(20) is a non-superconducting cuprate, which exhibits a doubling of the elementary cell along the c axis. Its optical conductivity sigma (omega) has been first measured here, down...
Lupi, S., Calvani, P., Capizzi, M., Roy, P.
An optical "pseudogap" is usually assumed to open at low T in the "anomalous Drude" absorption, which models the optical conductivity sigma(omega) (proportional to omega-1) of HCTS by a linewidth...
Evolution of a polaron band through the phase diagram of Nd[2-x]Ce[x]CuO[4-y] (1999)
Lupi, S., Maselli, P., Capizzi, M., Calvani, P., Giura, P., Roy, P.
The evolution with doping and temperature of the polaronic absorption in a family of high-T$_c$ superconductors is first followed here across the whole phase diagram. The polaron band softens with...
Infrared absorption from Charge Density Waves in magnetic manganites (1998)
Calvani, P., De Marzi, G., Dore, P., Lupi, S., Maselli, P., D'Amore, F., ...
The infrared absorption of charge density waves coupled to a magnetic background is first observed in two manganites La{1-x}Ca{x}MnO{3} with x = 0.5 and x = 0.67. In both cases a BCS-like gap 2 Delta...
Lupi, S., Capizzi, M., Calvani, P., Ruzicka, B., Maselli, P., Dore, P., ...
Reflectance measurements in properly selected samples of Nd$_{1.96}$Ce$_{0.04}$CuO$_{4+y}$ with different carrier concentrations provide a firm evidence of Fano antiresonances for the four transverse...
Optical conductivity of CuO_2 infinite-layer films (1997)
Dore, P., Calvani, P., De Marzi, G., Paolone, A., Lupi, S., Balestrino, G., ...
The infrared conductivity of CaCuO_2, SrCuO_{2-y}, and Sr_{0.85}Nd_{0.15}CuO_2 infinite-layer films is obtained from reflectivity measurements by taking into account the substrate contribution....
Small and large polarons in nickelates, manganites, and cuprates (1997)
Calvani, P., Dore, P., Lupi, S., Paolone, A., Maselli, P., Giura, P., ...
By comparing the optical conductivities of La_{1.67}Sr_{0.33}NiO_{4} (LSNO), Sr_{1.5}La_{0.5}MnO_4 (SLMO), Nd_2CuO_{4-y} (NCO), and Nd_{1.96}Ce_{0.04}CuO_{4} (NCCO), we have identified a peculiar...
Infrared response of ordered polarons in layered perovskites (1996)
Calvani, P., Paolone, A., Dore, P., Lupi, S., Maselli, P., Medaglia, P. G., ...
We report on the infrared absorption spectra of three oxides where charged superlattices have been recently observed in diffraction experiments. In La$_{1.67}$Sr$_{0.33}$NiO$_4$, polaron localization...
Polaronic optical absorption in electron-doped and hole-doped cuprates (1995)
Calvani, P., Capizzi, M., Lupi, S., Maselli, P., Paolone, A., Roy, P.
Polaronic features similar to those previously observed in the photoinduced spectra of cuprates have been detected in the reflectivity spectra of chemically doped parent compounds of...