We report the polarized optical reflectance of P4W14O50, the only charge-density-wave (CDW) superconductor in the monophosphate tungsten bronze family, over a wide frequency range. The 300-K infrared spectra are dominated by two-dimensional behavior: high reflectance with weak phonons in the conducting ab plane and low reflectance with strong vibrational modes along the interlayer direction anisotropic intra-t2g d→d excitation (∼ 10000 cm-1) reveals the "hidden" one-dimensional band structures in P4W14O50. The variable temperature ab-plane spectra clearly show a suppression of the optical conductivity along the b axis below 140 K, giving rise to charge localization and anisotropic CDW gap formation at ∼1400 cm-1. Although the oscillator strength is redistributed among the free-carrier response, the CDW gap absorption, and the d→d transition in the density wave states, the spectral weight is largely conserved below the plasma frequency. The ab-plane phonons become well resolved in the CDW states due to reduced screening. Based upon these observations, P4W14O50 is another example of a superconductor with an unusual normal state.
|Original language||English (US)|
|Number of pages||8|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Jun 1 2002|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics