Thursday, August 2, 2007

Jim Allen: Quasi-1D "Purple Bronze" Evidence for a new state of matter.

J. W. Allen, U. Michigan

"Evidence, arguments and challenges for showing a new quantum state of
matter in the normal phase of quasi-1D Li_0.9Mo_6O_17"

Jim Allen gave an extensive review of the highly anisotropic physics of Blue Bronze. This material is a quasi-1D conductor that develops superconductivity at 1.9 K. This system has a resistance anisotropy

rho|| : rho _|_ (1): rho _|_(2) = 1:10:25

Down to about 26K, rho|| follows a T^0.4 variation and rho _|_ follows a T^1.15 variation.
Below this temperature, both resistivities show an upturn. The upturn was initially thought to be the result of a spin or charge density wave, but susceptibilility, optics, photo-emission and X-ray diffraction seem to rule this out.

Jim described that ARPES appears to suggest this system is more likely to be a Luttinger Liquid, and in the spectra, they can see a holon peak and a spinon edge. The photo-emission spectra show a power-law A(E) ~ (E-E_F)^alpha, where alpha is temperature dependent .

This temperature dependent exponent can, it seems be understood in terms of a two band Luttinger Liquid, undergoing a cross-over from a two band fixed point to a one-band fixed point.

There are several questions raised by this system

  • Can the large t_perp (of order 100K) be reconciled with the quasi-one dimensional behavior seen at lower temperatures?
  • Band theory predicts two quasi-one dimensional bands, yet only one is observed in ARPES (figure above). Is this because a gap is starting to develop in the second band - and if so - can this be modelled theoretically?
  • Does the superconductivity restore the 3 dimensionality to the electron fluid?


Invertir en oro said...

Thanks for sharing this info because is very good and i like to post like this.

Viagra Canada said...

Yeah i can support this theory because I made my own theories what I don't approve is because some people believe that this is not gonna work.

Ideas de negocios said...

Thanks for taking the time to discuss this, but I am firmly convinced of this and love to learn more about the subject. If possible, acquire knowledge, would you update your blog with more information? It is very helpful to me

Octavia said...

Wow, there is a lot of useful data above!