Related papers: Anomalous T-dependence of phonon lifetimes in meta…
VO2 features concomitant structural and metal-insulator transitions. This poses a challenge for understanding the underlying mechanism: is the transition triggered by a structural or by an electronic instability? The two scenarios are…
The single crystal VO2, exihibiting a first-order metal-insulator transition (MIT) at 67.2 degrees C and an insulator-insulator transition (IIT) at ~49.7 degrees C, is grown. From synchrotron-based x-ray microdiffraction analysis, the IIT…
Raman scattering experiments have been performed on Na_xCoO_2 as function of temperature at the composition x=0.5 where a structural instability and a metal-insulator transition have been observed. Three additional phonon modes are observed…
Synchrotron X-ray total scattering studies of structural changes in rutile VO2 at the metal-insulator transition temperature of 340 K reveal that monoclinic and tetragonal phases of VO2 coexist in equilibrium, as expected for a first-order…
We present a Raman scattering study of Ca$_2$RuO$_4$, in which we investigate the temperature-dependence of the lattice dynamics and the electron-phonon interaction below the metal-insulator transition temperature ({\it T}$_{\rm MI}$).…
We apply ultrafast spectroscopy to establish a time-domain hierarchy between structural and electronic effects in a strongly-correlated electron system. We discuss the case of the model system VO2, a prototypical non-magnetic compound that…
In femtosecond pump-probe measurements, the appearance of coherent phonon oscillations at 4.5 THz and 6.0 THz indicating the rutile metal phase of VO_2 does not occur simultaneously with the first-order metal-insulator transition (MIT) near…
Polarized Raman scattering spectra of the K_xCo_{2-y}Se_2 single crystals reveal the presence of two phonon modes, assigned as of the A_{1g} and B_{1g} symmetry. Absence of additional modes excludes the possibility of vacancy ordering,…
Vanadium dioxide (VO$_{2}$) undergoes a first-order metal-insulator transition (MIT) upon cooling near room temperature, concomitant with structural change from rutile to monoclinic. Accurate characterization of lattice vibrations is vital…
Vanadium dioxide (VO2) undergoes a phase transition at a temperature of 340 K between an insulating monoclinic M1 phase and a conducting rutile phase. Accurate measurements of possible anisotropy of the electronic properties and phonon…
We report a Raman study of the effect of temperature on the self-energies of optical phonons in a number of transition metals with hexagonal-close-packed structure. Anisotropic softening of phonon energies and narrowing of phonon linewidths…
To explore the driving mechanisms of the metal-insulator transition (MIT) and the structural transition in VO2, we have investigated phonon dispersions of rutile VO2 (R-VO2) in the DFT and the DFT+U (U : Coulomb correlation) band…
The temperature dependence of the Mott metal-insulator transition (MIT) is studied with a VO_2-based two-terminal device. When a constant voltage is applied to the device, an abrupt current jump is observed with temperature. With increasing…
The anharmonic properties of the low-frequency E2 phonon in ZnO were measured using impulsive stimulated Raman scattering. At 5 K, the frequency and lifetime are (2.9787 +/- 0.0002) THz and (211 +/- 7) ps. The unusually long lifetime and…
We measure the temperature dependence of the Raman spectra of metallic and semiconducting nanotubes. We show that the different trend in metallic tubes is due to phonon re-normalization induced by the variation in electronic temperature,…
A crack free and high structural quality Sr2Nb2O7 single crystals were grown by the optical float zone method using optimized growth parameters. Laue pattern confirms single crystalline nature of the grown crystal. Temperature dependent…
We report the simultaneous measurement of the structural and electronic components of the metal-insulator transition of VO$_2$ using electron and photoelectron spectroscopies and microscopies. We show that these evolve over different…
The ultrafast photoinduced insulator-metal transition in VO2 is studied at different temperatures and excitation fluences using multi-THz probe pulses. The spectrally resolved mid-infrared response allows us to trace separately the dynamics…
We report on temperature dependence of acoustic phonon-induced resistance oscillations in very high mobility two-dimensional electron systems. We observe that the temperature dependence is non-monotonic and that higher order oscillations…
We have carried out temperature-dependent x-ray diffraction and Raman scattering experiments on powder $Cs_3Bi_2Br_9$. Trigonal to monoclinic structural transition at around 95 K is discussed and shown to be driven by the softening of the…