drexel oral qualifying exam presentation
DESCRIPTION
Presentation slides for my oral qualifying exam for PhD candidacy at Drexel University.TRANSCRIPT
Interaction Between Magnetism and
Superconductivity
Jeremie Doehla
Adviser: Dr. Goran Karapetrov
Department of Physics
Drexel University
June 4, 2013
Magnetism
Ferromagnetism● Spontaneous spin
alignment
● Long range order
Diamagnetism● Negative magnetic
susceptibility
● Perfect diamagnetism = Meissner effect
Superconductivity
● Perfect diamagnet
● Long range order
● BCS theory
– Low temperature
– Absence of magnetic field
● Type I
● Type II – vortex state
Ferromagnetic-Superconductor Hybrids
● A superconducting state may be induced by a magnetic field.
Applied Magnetic Field
Fre
e E
nerg
y (F
)
Proximity Effect
● When in contact with a normal or ferromagnetic material there is a penetration of the cooper pairs into said material.
● Ginzburg-Landau Equation:
KxFe
2-ySe
2
● New materials (2008)
● Each phase may have a different magnetic order
● 1 phase found to be superconducting
● KFe2Se2-z
● K2Fe4Se5
● Two structures of KFe2Se2
(different charge orderings)
● And Others
FeSe KFe2Se
2
KxFe
2-ySe
2: Crystal Growth
● Step 1: FeSe(vapor self transport)
● Step 2: KFe2Se
2
(from melt)
● Post annealing/ quenching
● Contamination concerns
KxFe2-ySe2: Characterization
● Why is it a superconductor?
● How do the different phases interact with each other and behave independently?
Techniques:● X-Ray Diffraction
● Resistance
● Hall effect
● Magnetization
CharacterizationX-Ray diffraction:
● Crystal structure characterization
● Different crystal phases will have different characteristic peaks
Resistivity:
● CDW
● Varies greatly with stoichiometry
CharacterizationHall Effect
● Charge carrier
● FeSe has been found to have a change in the sign of the hall effect
Magnetization
● Hc1, Hc2, magnetic susceptibility
Conclusion
KxFe
2-ySe
2
● Behavior of each phase individually
● Interaction between the different phases
In General● Why high temperature
superconductors form
● Further investigate the fundamental relationship between magnetization and superconductivity
References● Ashcroft and Mermin. Solid State Physics. Brooks, Belmont, CA, 1976.● A. I. Buzdin. Proximity eects in superconductor-ferromagnet heterostructures. Reviews of modern physics, 77, July
2005.● T.-L. Xia D. M. Wang, J. B. He and G. F. Chen. Eect of varying iron content on the transport properties of the
patassium-intercalated iron selenide k(x)fe(2-y)se(2). Physical Review B, 83, 2011.● Bing Shen Zhen-yu Wang Chun-Hong Li Fei Han, Huan Yang and Hai-Hu Wen. Metastable superconducting state in
quenched k(x)fe(2-y)se(2). Philosophical Magazine, 92, July 2012.● Kuo-Wei Yeh Ta-Kun Chen Tzu-Wen Huang Phillip M.Wu Yong-Chi Lee Yi-Lin Huang Yan-Yi Chu Der-Chung Yan Fong-
Chi Hsu, Jiu-Yong Luo and Maw-Kuen Wu. Superconductivity in the pbo-type structure alpha-fese. Proceedings of the National Academy of Sciences, 105(38), September 2008.
● M. Decroux-O. Fischer G. Remenyi H. W. Meul, C. Rossel and A. Briggs. Observation of magnetic-eld-induced superconductivity. The American Physical Society, 53(5), July 1984.
● V. Jaccarino and M. Peter. Ultra-high-eld superconductivity. Physical Review Letters, 9(7), October 1962.● Genda Gu J M Tranquada Jinsheng Wen, Guangyong Xu and R J Birgeneau. Interplay between magnetism and
superconductivity in iron-chalcogenide superconductors: crystal growth and characterizations. Reports on Progress in Physics, 74, September 2011.
● Hirano Kamihara, Watanabe and Hosono. Iron-based layered superconductor la[o(1-x)f(x)]feas(x = 0.05-0.12). Journal of the American Chemical Society, 130, March 2008.
● Charles Kittel. Introduction to Solid State Physics. John wiley and Sons, Inc., USA, 2005.● I. F. Lyuksyutov and V. L. Pokrovsky. Ferromagnet-superconductor hybrids. Advances in Physics, 54(1), 2005.● Ksenofontov Felser Xu Zandbergen Hor Allred Williams Qu Checkelsky Ong McQueen, Huang and Cava. Extreme
sensitivity of superconductivity to stoichiometry in fe1+delta se. Physical Review B, 79, January 2009.● Davin J. Morgan and J. B. Ketterson. Asymmetric ux pinning in a regular array of magnetic dipoles. Physical Review
Letters, 80(16), April 1998.● A.C. Rose-Innes and E.H. Rhoderick. Introduction to Superconductivity. Pergamon Press Ltd., Elmsford, New York,
1978.● T. Terashima T. Yakabe Y. Terai M. Tokumoto A. Kobayashi H. Tanaka S. Uji, H. Shinagawa and H. Kobayashi.
Magnetic-eld-induced superconductivity in a two-dimensional organic conductor. Letters to nature, 410, April 2001.● Applied Superconductivity and Cryoscience Group. Lectures on superconductivity. Technical report, University of
Cambridge.● S. H. Yu S. Avci Z. L. Xiao H. Claus J. Schlueter V. V. Vlasko-Clasov U. Welp U. Patel, J. Hua and W. K. Kwok. Growth
and superconductivity of fese(x) crystals. Applied Physics Letters, 94, 2009.● Zhi Li Peng Deng Kai Chang Ke He Shuaihua Ji Lili Wang Xucun Ma Jiang-Ping Hu Xi Chen Wei Li, Hao Ding and Qi-
Kun Xue. Kfe(2)se(2) is the parent compound of k-doped iron selenide superconductors. Physical Review Letters, 109, 2012.
Acknowledgments
● Petra Husanikova● Christopher Brown● Joey Lambert● Erica Smith
Sample carrier design
● Needs to fit down the central shaft of dewar
● Space considerations
● Thermal considerations
● Vacuum considerations
● Electrical contacts
– Sensors
– Utility● Replaceable parts
Sample carrier design
● Still a work in progress
● Temperature sensor
● Heating
● Electrical leads
Crystal Growth and Measurements done
(although, not related to KxFe2-xSe2)● CuxTiSe2
● Iodine vapor transport
● Grown on Temple's campus(same place we will grow KxFe2-xSe2)
Measurements:● Resistance vs.
temperature
Temperature (K)
Res
ista
nce
mea
sur e
d