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Highlights on Some Experimental Progress of FeSe Xingjiang ZHOU 2014/10/08

Highlights on Some Experimental Progress of FeSe Xingjiang ZHOU 2014/10/08. Bulk FeSe Superconductor. F.-C. Hsu et al., PNAS 105 (2008) 14262;. S . Medvedev et al., Nat . Mater. 8 (2009) 630. N . Katayama et al ., J . Phys. Soc. Jpn . 79 (2010)113702. Simple crystal structure;

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Highlights on Some Experimental Progress of FeSe Xingjiang ZHOU 2014/10/08

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  1. Highlights on Some Experimental Progress of FeSe Xingjiang ZHOU 2014/10/08

  2. Bulk FeSe Superconductor • F.-C. Hsu et al., PNAS 105 (2008) 14262; S. Medvedev et al., Nat. Mater. 8 (2009) 630. N. Katayama et al., J. Phys. Soc. Jpn. 79 (2010)113702. • Simple crystal structure; • In FeSe, Tc can be enhanced from 8.5K to 36.7K at high pressure; • In Fe(SexTe1-x), Tc can reach 14.5K.

  3. FeSe Films Grown on Graphene ~30-Layer 8-Layer 2-Layer C. L. Song et al., Phys. Rev. B 84 (2011) 020503(R). C. L. Song et al., Science 332 (2011) 1410. • Single-layer FeSe/Graphene is non superconducting above 2.2K; • Tc increases with the number of layers in FeSe/Graphene films, • reaching 8K for 8 layers with a superconducting gap of 2.1 meV; • V-shaped STS curve in the superconducting state indicating a • node in the gap function.

  4. FeSe Films Grown on SrTiO3 (001) Single-layer, Tc ~ 80 K? Double-layer, semiconducting 20.1meV Q. Y. Wanget al., Chinese Phys. Lett. 29 (2012) 037402. 9.5meV • Single-layer FeSe/SrTiO3 film shows a STS peak at ~20 meV, • corresponding to an estimated Tc~80 K if it is superconducting; • Double-layer FeSe/SrTiO3 film is semiconducting.

  5. Distinct Electronic Structure of Superconducting FeSe/SrTiO3 Films Cut 2 Cut 1 D. F. Liu et al., Nature Communications 3 (2012) 931. Distinct electronic structure: no Fermi surface near G, only electron-like Fermi surface near M.

  6. Phase Diagram and Indication of Tc~65K in Single-Layer FeSe/SrTiO3 Film Tc~65 K 2D/kTc=6~7 S. L. He et al., Nature Materials 12, 605 (2013). • There are two phases present in single-layer FeSe/SrTiO3 film • with different electronic structure (N phase and S phase); • By annealing in vacuum, N phase can transform into S phase; • Indication of Tc~65 K observed.

  7. Layer-Dependent Electronic Structure in FeSe/SrTiO3 Films S. Y. Tan et al., Nature Materials 12, 634 (2013). • For two-layer or multiple layer FeSe/SrTiO3 films, it is reported • that SDW state is formed; • The SDW temperature decreases with increasing number • of FeSe layers.

  8. Substrate Strain-Dependent Electronic Structure and Superconductivity of Single-layer FeSe Film FeSeBR: SL-FeSe/Nb:BaTiO3/KTaO3heterostructures, relaxed; a=3.76 A FeSeBU: SL-FeSe/Nb:BaTiO3/KTaO3heterostructures, unrelaxed; a=3.99 A FeSeSX: SL FeSe/Nb:SrTiO3/KTaO3heterostructures; a=3.99 A FeSeS: FeSe/Nb:SrTiO3 ; a=3.906 A R. Peng et al., Nature Communications 5 (2014) 5044. • The lattice constant changes from 3.76 A to 3.99 A, • Tc shows little change near (70+_5)K; • The superconductivity is not sensitive to strain of the substrate.

  9. Replica Bands and Electron-Phonon Coupling in Single-layer FeSe/SrTiO3 Film J. J. Lee et al., arXiv: 1312.2633. • Replica bands are observed with a separation of ~100 meV; • It is proposed this is due to electron coupling with STO phonon.

  10. Transport and Magnetic Measurements on Single-Layer FeSe/SrTiO3 Films Magnetism Resistivity W. H. Zhangetal., Chinese Physics Letters 31 (2014) 017401. Both transport and magnetic measurements indicate single-layer FeSe/SrTiO3 is superconducting although the Tc is not as high as that from ARPES.

  11. arXiv: 1406.3435.

  12. Schematic of 4 point probe (4PP）transport measurement setup. J. F. Ge et al., arXiv: 1406.3435.

  13. Temperature and external magnetic field dependence of electrical transport property of a single-layer film of FeSe 11T 3K J. F. Ge et al., arXiv: 1406.3435.

  14. 4PP transport measurement on Bi2212 crystal (Tc~90K) with measurement configurations of C1423 (a) and C1234 (b), respectively. J. F. Ge et al., arXiv: 1406.3435.

  15. Temperature dependence of electrical transport property of another FeSe/STO sample measured with the 100-μm-tip-separation 4PP fixed at one measuring location while temperature was increasing. J. F. Ge et al., arXiv: 1406.3435.

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