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    Title: 鈰鈷銦晶體及釕錫摻雜對超導的影響
    Ru and Sn double doping effects on superconductivity of CeCoIn5
    Authors: 羅裕國
    Lo, Yu Kuo
    Contributors: 陳洋元
    Chen,Yang Yuan
    羅裕國
    Lo, Yu Kuo
    Keywords: 超導
    superconductor
    Date: 2013
    Issue Date: 2014-09-01 13:48:38 (UTC+8)
    Abstract: 重費米子系統CeCoIn5同時具有超導態(TC= 2.3 K)與反鐵磁態(TN= 3.8 K)的特性,此一系統很適宜研究量子臨界點(QCP)問題亦即利用摻雜使超導溫度消失或壓抑至0度。研究指出藉由摻雜錫(Sn)取代部分銦(In)改變CeCoIn5的電子結構使其合成CeCoIn5-xSnx會使得超導溫度有所改變,其Tc隨著摻雜濃度x的提升呈現線性關係下降;若摻雜Ru部份取代Co合成CeCo1-yRuyIn5 晶體,隨著Ru濃度y的上升其超導溫度亦會呈線性關係下降。在這篇論文中為了研究相轉變溫度與摻雜濃度的關係,我們決定同時結合上述兩者的摻雜條件,同時摻雜Ru(電洞摻雜)與Sn(電子摻雜),希望可以在避免大幅改變其電子結構的狀態下去觀察超導溫度如何被壓抑以觀察在QCP附近狀態改變的機制。
    我們以銦做為溶劑,使用助溶劑法(indium-flux method)成長CeCo1-yRuyIn5-xSnx 晶體。並且使用X-ray粉末繞射儀與SEM做初步的結構與成分分析,判斷是否有CeCoIn5的相位並從中挑出單晶。接著分別對單晶的樣品進行磁性、電性、低溫比熱的量測,磁性的量測以檢視樣品是否有超導行為。從電阻、低溫比熱的結果觀察到雙摻雜樣品其超導溫度TC有明顯的降低,在不同的摻雜情形下,無參雜CeCoIn5晶體之Tc為2.3 K,CeCo0.8Ru0.2In5晶體之TC為2.2 K,而雙摻雜Ru與Sn之CeCo0.8Ru0.2In4.9Sn0.1之晶體TC為1.53 K,比較無摻雜及單摻雜之樣品,其TC皆已大幅下降,惟無法降到0度。顯然研究CeCo1-yRuyIn5-xSnx 晶體量子臨界點現象單單摻雜是不夠的,或許改變其他參數,如加壓或磁場可達到此一目的。
    Heavy fermion system CeCoIn5 exhibits both superconducting and antiferromagnetic states with TC= 2.3 K and TN= 3.8 K respectively. It is a good candidate for the study of quantum critical point (QCP), i.e., the superconducting temperature can be suppressed to zero by doping or external applied pressure, etc. Based on the previous studies, the Sn doped CeCoIn5-xSnx would change the electronic structure and lower its superconducting temperature; Ru doped CeCo1-yRuyIn5 would also linearly decreases its superconducting temperature as well. In this thesis, we tried to double-dope Ru (hole doping) and Sn (electron doping) into CeCoIn5 system and observe its physical properties as the suppressed superconducting temperature approachs to zero by maintaining its number of valance electrons. All CeCoIn5 single crystals are synthesized by indium-flux method, and their single-phase crystal structures are confirmed by X-ray powder diffraction analysis.
    The magnetic susceptibility data measured by the Superconducting Quantum Interference Device Magnetometer (SQUID) shows the superconducting behavior and the quality of these single crystals. Moreover, the electrical resistivity and the specific heat measurements indicate the decreasing of the superconducting temperature. The un-doped sample CeCoIn5, TC is 2.3 K, whereas the superconducting temperature of Ru-doped sample (CeCo0.8Ru0.2In5) is dereeased toward 2.2 K. However, for the double-doped sample of CeCo0.8Ru0.2In4.9Sn0.1, its superconducting temperature is decreased to 1.53 K, which is greatly decreased as compared with the un-doped or single doped specimens. Obviously to suppress the superconducting temperature to zero, other parameters such as external pressure or applied magnetic field etc. are required.
    Reference: [1] M. Daniel et al., Phys. Rev. Lett.95, 016406 (2005)
    [2] P.G. Pagliuso et al., Phys. Rev B 100503 (2001)
    [3] M.N. Ou et al., Phys. Rev. B 00 005100 (2013)
    [4] E.D. Bauer et al., Phys. Rev. Lett.94, 047001 (2005)
    [5] P.G. Pagliuso et al., Physica B 312-313(2002) 129-131
    [6] C. Petrovic et al., J.Phys.:Condens. Matter 13 (2001)L337-L342
    [7] L.D. Pham et al., Phys. Rev. Lett.97, 056404 (2006)
    [8] E.D. Bauer et al., Physica B 378-380(2006) 142-143
    [9] H.Hehher et al., Phys. Rev. Lett.84, number21 (2000)
    [10] C Petrovic et al., J. Phys.: Condens. Matter 13 (2001) L337-L342
    [11] 洪慈蓮,釔鋇銅氧化合物與二鋁化鈰奈米微粒之物性探討,清華大學碩士論文(2008)
    Description: 碩士
    國立政治大學
    應用物理研究所
    101755014
    102
    Source URI: http://thesis.lib.nccu.edu.tw/record/#G1017550141
    Data Type: thesis
    Appears in Collections:[應用物理研究所 ] 學位論文

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