Skip to Main Content
 

Global Search Box

 
 
 
 

Files

ETD Abstract Container

Abstract Header

Studies of thermal phase fluctuations in severely underdoped YBCO films

Zuev, Yuri L.

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Chemical Physics.
One of the central problems in the area of high-T C superconductivity is the origin of the so-called pseudogap , its relationship to superconductivity and peculiar normal state properties of cuprates. One point of view, very popular in the field, is that opening of the pseudogap is caused by thermal phase fluctuations (i.e. thermal fluctuations of the phase of the superconducting order parameter). In this work I have attempted to address the role of thermal phase fluctuations experimentally by studying their effect on superfluid density. The experimental challenge in this area is to produce samples homogeneous enough that most of superfluid density temperature dependence is unobscured by inhomogeneities. This is very difficult because in the interesting regime, i.e. heavily underdoped samples with transition temperatures 40K and below, T C varies rapidly with carrier concentration, and minute oxygen inhomogeneities cause severe variations of T C across a given sample. This challenge has been successfully met and I was able to produce homogeneous enough sample, such that it was possible to draw quantitative conclusions from our data. Carrier doping in CuO 2 planes could be varied by two techniques: changing number of oxygen atoms in the CuO chains (therefore changing the chemical composition of the sample), or changing the degree of order within chains (without overall change in composition). The results of this work prove to be insensitive to a particular way of carrier concentration adjustment. I see no evidence of strong role of thermal phase fluctuations in my thin films. Individual CuO 2 layers are coupled strongly almost all the way to T C , and the suppression of the transition temperature by fluctuations is by a few degrees at most. There is no evidence of T C suppression by several hundred degrees as is envisioned by fluctuation-mediated pseudogap model. Transition temperature is not proportional to T C , rather it is proportional to T C 2.3 . This is also contrary to the picture of superconducting transition in HTSC as phase-ordering transition. Magnetic field was applied parallel to the layers as a way to decouple them. The dependence of the films inductance on the magnetic field indicate very strong effect of the vortices located between CuO 2 planes. The experimental findings are compared to theory and shortcomings of the experiment and analysis are considered.
Gregory Lafyatis (Advisor)
126 p.

Recommended Citations

Citations

  • Zuev, Y. L. (2005). Studies of thermal phase fluctuations in severely underdoped YBCO films [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1124987327

    APA Style (7th edition)

  • Zuev, Yuri. Studies of thermal phase fluctuations in severely underdoped YBCO films. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1124987327.

    MLA Style (8th edition)

  • Zuev, Yuri. "Studies of thermal phase fluctuations in severely underdoped YBCO films." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1124987327

    Chicago Manual of Style (17th edition)