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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Pressure and doping effects on the anomalous phase transition in ternary superconductor Bi2Rh3Se2

Chen, Ching-Yuan 23 July 2012 (has links)
Bi2Rh3Se2 have been known as a charge-density-wave (CDW) superconductor, where the superconducting critical temperature Tc and the CDW phase transition are about 0.7 K and 250 K, respectively. Since there has no definite proof that the anomaly at around 250 K comes from charge-density-wave, we wished to provide another evidence to study whether the superconductor had the properties of CDW by electric resistivity measurements applied different pressures. Bi2Rh3Se2 was prepared by using the solid state reaction method and heating in the quartz tube. After the sample was synthesized, the quality was identified by XRD, MPMS, and specific heat probe. With the confirmation of the above-mentioned measurements, we can determine the sample¡¦s quality is good. Furthermore, temperature-dependent resistivity (2-340 K) under pressure (up to 22.23 kbar) on the ternary superconductor Bi2Rh3Se2 are performed to study the possible coexistence of CDW and superconductivity. Interestingly, the resistive anomaly occurred at Ts~250 K, is shifted to higher temperature with increasing pressure. This experimental finding is not consistent with a traditional CDW transition. Moreover, the temperature-dependent Transmission Electron Microscopy (TEM) electron diffraction is evident a structural phase transition from space group ¡§C1 2/m 1¡¨ (Ts > 250 K) to ¡§P1 2/m 1¡¨ (Ts < 250 K). Finally, We do the Co doping to make sure the effects of chemical pressure on this phase transition. The results are opposite to imposed by physical pressure that the transition is shift to lower temperature with more Co inside the sample.

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