Charge density wave in hidden order state of URu2_2Si2_2

We argue that the hidden order state in URu$_2$Si$_2$ will induce a charge density wave. The modulation vector of the charge density wave will be twice that of the hidden order state, $Q_{CDW} = 2Q_{HO}$. To illustrate how the charge density wave arises we use a Ginzburg-Landau theory that contains a coupling of the charge density wave amplitude to the square of the HO order parameter $\Delta_{HO}$. This simple analysis allows us to predict the intensity and temperature dependence of the charge density wave order parameter in terms of the susceptibilities and coupling constants used in the Ginzburg-Landau analysis.Comment: 8 pages, 4 figure

Properties of charge density waves in La2−x_{2-x}Bax_{x}CuO4_4

We report a comprehensive x-ray scattering study of charge density wave (stripe) ordering in $\rm La_{2-x}Ba_xCuO_4 (x \approx 1/8)$, for which the superconducting $T_c$ is greatly suppressed. Strong superlattice reflections corresponding to static ordering of charge stripes were observed in this sample. The structural modulation at the lowest temperature was deduced based on the intensity of over 70 unique superlattice positions surveyed. We found that the charge order in this sample is described with one-dimensional charge density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0, 0.23, 0.5) respectively on neighboring $\rm CuO_2$ planes. The structural modulation due to the charge density wave order is simply sinusoidal, and no higher harmonics were observed. Just below the structural transition temperature, short-range charge density wave correlation appears, which develops into a large scale charge ordering around 40 K, close to the spin density wave ordering temperature. However, this charge ordering fails to grow into a true long range order, and its correlation length saturates at $\sim 230\AA$, and slightly decreases below about 15 K, which may be due to the onset of two-dimensional superconductivity.Comment: 11 pages, 9 figure

Chemical pressure and hidden one-dimensional behavior in rare earth tri-telluride charge density wave compounds

We report on the first optical measurements of the rare-earth tri-telluride charge-density-wave systems. Our data, collected over an extremely broad spectral range, allow us to observe both the Drude component and the single-particle peak, ascribed to the contributions due to the free charge carriers and to the charge-density-wave gap excitation, respectively. The data analysis displays a diminishing impact of the charge-density-wave condensate on the electronic properties with decreasing lattice constant across the rare-earth series. We propose a possible mechanism describing this behavior and we suggest the presence of a one-dimensional character in these two-dimensional compounds. We also envisage that interactions and umklapp processes might play a relevant role in the formation of the charge-density-wave state in these compounds.Comment: 8 pages, 5 figure

Amplitude `Higgs' mode in 2H-NbSe2 Superconductor

We report experimental evidences for the observation of the superconducting amplitude mode, so-called `Higgs' mode in the charge density wave superconductor 2H-NbSe2 using Raman scattering. By comparing 2H-NbSe2 and its iso-structural partner 2H-NbS2 which shows superconductivity but lacks the charge density wave order, we demonstrate that the superconducting mode in 2H-NbSe2 owes its spectral weight to the presence of the coexisting charge density wave order. In addition, temperature dependent measurements in 2H-NbSe2 show a full spectral weight transfer from the charge density wave mode to the superconducting mode upon entering the superconducting phase. Both observations are fully consistent with a superconducting amplitude mode or Higgs mode.Comment: Accepted for publication in Phys. Rev. B Rapid Com. 5 pages with 3 figure

Coexistent State of Charge Density Wave and Spin Density Wave in One-Dimensional Quarter Filled Band Systems under Magnetic Fields

We theoretically study how the coexistent state of the charge density wave and the spin density wave in the one-dimensional quarter filled band is enhanced by magnetic fields. We found that when the correlation between electrons is strong the spin density wave state is suppressed under high magnetic fields, whereas the charge density wave state still remains. This will be observed in experiments such as the X-ray measurement.Comment: 7 pages, 15 figure

The Wave Function and Quantum Reality

We investigate the meaning of the wave function by analyzing the mass and charge density distribution of a quantum system. According to protective measurement, a charged quantum system has mass and charge density proportional to the modulus square of its wave function. It is shown that the mass and charge density is not real but effective, and it is formed by the ergodic motion of a localized particle with the total mass and charge of the system. Moreover, it is argued that the ergodic motion is not continuous but discontinuous and random. This result suggests a new interpretation of the wave function, according to which the wave function is a description of random discontinuous motion of particles, and the modulus square of the wave function gives the probability density of the particles being in certain locations. It is shown that the suggested interpretation of the wave function disfavors the de Broglie-Bohm theory and the many-worlds interpretation but favors the dynamical collapse theories, and the random discontinuous motion of particles may provide an appropriate random source to collapse the wave function.Comment: 8 pages, no figure