Thermodynamics and optical conductivity of unconventional spin density waves

Abstract

PACS. 75.30.Fv Spin-density waves – 71.45.Lr Charge-density-wave systems – 78.30.Jw Organic compounds, polymers,

Raman scattering versus infrared conductivity: Evidence for one-dimensional conduction inLa2−xSrxVenturini1, Zhang2, Hackl3 et al. 2002Phys. Rev. B449310View full textAdd to dashboardCite

“…In crystals or subunits such as the CuO 2 planes with a center of inversion the mutual exclusion principle holds, and IR-active (odd or polar) excitations cannot be observed in the Raman spectrum (even excitations) and vice versa 18 . In addition, due to the coherence factors collective phenomena such as superconductivity or density waves which are a possible way to look at charge ordering lead to different spectra in the Raman response and in the conductivity 19,20 . For instance, in the superconducting state the Raman response is characterized by a pile up of spectral weight around 2∆ 0 while the conductivity is partially or fully suppressed below twice the gap, and the weight is transferred towards ω = 0.…”

Unconventional charge density wave in coupled electron-phonon system

“…This situation is similar to the development of a CDW in an interacting electron system: in the simple Hubbard model the interaction U < 0 is not able to drive the system into an unconventional charge density wave ground state either, and one has to include two center exchange integrals as well to facilitate an unconventional condensate. 9,13,15 With all this…”

“…9 The thermodynamics of the system in the low temperature phase is determined solely by the momentum dependence of E(k), and the possible node structure (line or point nodes) on the Fermi surface, if there are any. Thus in the followings we explore the momentum dependence of the order parameter.…”

UNCONVENTIONAL SPIN DENSITY WAVE IN (TMTSF)2PF6 BELOW T = 4.2 K

“…We propose that the anomaly at T ⋆ ≈ 4 K in (TMTSF) 2 PF 6 signals the appearance of USDW. We point out that USDW requires more subtle balance between different interaction terms than conventional SDW, 15 and consequently it is perhaps not easily find in other Bechgaard salts.…”

“…15,16,17,18,19 Unlike the conventional SDW, the USDW is defined as the SDW where the order parameter ∆(k) depends on the quasi-particle momentum k. In spite of a clear thermodynamic signal (as in the usual mean field-like transition), the first order term in ∆(k), corresponding to local charge or local spin, is invisible. Consequently, these states may be called the phase with hidden order parameter.…”