Our research area is experimental condensed matter physics. We study the electronic properties of strongly correlated materials. Systems of interest to us include high-T_c cuprates,
Fe-pnictides, cobaltates, manganites, ruthenates, and other transition-metal compounds. The behaviors of electrons in those materials and systems are usually described as “novel”, “unconventional”, “strange”.…. The complex interplay between charge, spin, lattice as well as orbital degrees of freedom makes those materials very challenging area in condensed matter physics. Other systems of interest to us over the years include organic charge-transfer salts and conducting polymers. The members in our group
work on different physical measurement techniques, including infrared and optical spectroscopy, specific heat, transport and magnetic measurements. They also devoted much effort to the growth of single crystals of fundamental interest to the condensed matter physics community by flux and optical floating-zone methods.
We work closely with colleagues in theoretical and experimental condensed matter physics at Institute of Theoretical Physics of CAS, Tsinghua University, University of Science and Technology of China and many other labs around the world. We interact with experts in other specialties in condensed matter physics and materials science.
Contribution to the development and
understanding of Fe-based superconductors at the early stage:
confirmed the superconductivity at 26 K in F-doped LaFeAsO shortly
after it was reported by Hosono’s group, did the first
comprehensive study on the physical properties of the novel
superconductors by performing magnto-transport and infrared
measurements, and posted the first paper on FeAs based
superconductors on the preprint server arXiv.org
(arXiv:0803.0128, later published in PRL 101, 057007 (2008)).
The work, which was highlighted in Naure Asia Materials under the title:
Superconductors: Birth of the iron age, helped initiate the explosive research in this field.
We, together with our theoretical
colleagues, identified a
spin density wave (SDW) ordered state for the parent compound and
revealed a competing phenomenon between superconductivity and SDW
instability based on transport, optical measurement and first
(arXiv:0803.3426, published in EPL 83, 27006 (2008)), which was subsequently confirmed by
neutron scattering experiment. We promoted the
superconducting transition temperature to beyond 40 K by replacing
La with rare earth element Ce
(arXiv:0803.3790, published in PRL 101, 057007 (2008)), which is one of the first two
independent works on rare earth element substitutions.
The work was highlighted in Nature China under the title:
High-temperature superconductivity: Warmer than expected..
did the first optical spectroscopy study on single crystal samples
of parent compounds and revealed SDW gap formation on parts of the
Fermi surfaces accompanied by rather steep reductions in both
carrier scattering rate and Drude spectral weight (PRL 101,
257005 (2008)). The work
provides profound experimental evidence for the itinerant origin
of spin density wave order. We
also did the first optical spectroscopy study on single crystal
samples of superconducting compounds, identified a pairing gap
formation in optical conductivity spectrum with an s-wave pairing
lineshape, and revealed by spectral weight analysis the
fulfillment of the Ferrell-Glover-Tinkham sum rule at low energy
scale, which thus elucidates the significant difference between
the Fe pnictide and high-Tc cuprate superconductors
(PRL 101, 107004 (2008)).
A general description of our early contribution could be found in a
report entitled "Research progresses shed
light on superconductivity mechanism" in the CAS journal
《Bulletin of the Chinese Academy of Sciences》. More detailed
record could be found in a Chinese article by information
researchers from Wuhan Branch of National Science Library of CAS "Research
progress in synthesis of Fe-based superconducting materials"
published in 《科学通报》(Bulletin of Science).