2D superconductivity

The goal of our research:

l  Search interfacial high temperature superconductors by a favorable combination of high density of states, high-frequency phonons, and strong e-ph coupling.

l  Address the key open questions in high temperature superconductors (HTS), such as the origin of pseudogap and the ‘glue’ responsible for electron pairing.

Our approach to this goal is to:

• Utilize Molecular Beam Epitaxy (MBE) synthesis to fabricate atomically smooth thin films and superlattices on various dielectric substrates
• Utilize argon-ion bombardment to obtain diversified layers of HTS
• Manufacture various HTS devices and nano-structures
• Perform scanning tunneling spectroscopy, angle-resolved photoemission spectroscopy and transport measurements

Our main achievements:

Ø  Mapping the electronic structure of each ingredient oxide layer of high-T_c cuprate superconductor Bi₂Sr₂CaCu₂O_8+δ, Phys. Rev. Lett. 115, 237002 (2015). Phys. Rev. B93, 140504(R) (2016).

Ø  Interface induced high temperature superconductivity in single unit cell of FeSe on SrTiO₃, Chin. Phys. Lett. 29, 037402 (2012); Nat. Commun. 3, 931 (2012); Nat. Mater. 12, 605(2013); Chin. Phys. Lett. 31, 017401 (2014); Phys. Rev. B 89, 060506(R) (2014); J. Phys.: Condens. Matter 26, 265002 (2014); Phys. Rev. B 90, 214513 (2014); Sci. Rep. 4, 6040 (2014); Nat. Commun. 5, 5047 (2014); PNAS 111, 18501 (2014); Nat. Mater. 14, 285(2015); Phys. Rev. B 91, 060509(R) (2015); Phys. Rev. B 92, 180507(R) (2015); Phys. Rev. Lett. 114, 037002 (2015); Phys. Rev. B 91, 220503 (2015). 2D Mater.3 024002(2016); Phys. Rev. B93, 020507(R) (2016); Phys. Rev. B93, 075428 (2016); Phys. Rev. Lett.116, 107001 (2016); Appl. Phys. Lett.108, 202603 (2016)

Ø  Detection of a superconducting phase in a two-atom layer of hexagonal Ga film grown on semiconducting GaN(0001), Phys. Rev. Lett. 114, 107003 (2015).

Ø  Quantum Griffiths singularity of superconductor-metal transition in Ga  thin films, Science 350, 542 (2015).

Ø  Direct observation of nodes and twofold symmetry in FeSe supercondutors, Science 332, 1410 (2011); Phys. Rev. B 84 020503 (2011); Phys. Rev. Lett. 109 137004(2012); Phys. Rev. Lett.112, 057002 (2014).

Ø  Phase separation and magnetic order in K_xFe_2-ySe₂, Nat. Phys. 8 126 (2012); Phys. Rev. Lett. 109 057003(2012).

Ø  Superconductivity in one-atomic-layer In/Pb films grown on Si(111), Nat. Phys. 6, 104 (2010).