Welcome to the Neutron Scattering Group!

 

We are an experimental group utilizing neutron scattering technique combined with other probes such as X-ray scattering and transport to do cutting-edge research on quantum materials including: high-Tc superconductors, quantum spin liquids, and topological materials, etc. The scattering experiments are carried out in neutron and light sources overseas. At Nanjing University, we mantain a lab growing single crystals and performing characterizations. Please contact us for any questions or collaboration opportunities. We look forward to your joining us!

Updates

 

2018-06-17

Unusual response to the superconducting transition in an In-doped topological crystalline insulator

 

Our group published a paper entitled "Unusual phonon density of states and response to the superconducting transition in the In-doped topological crystalline insulator Pb0.5Sn0.5Te" in PRB as a Rapid Communication [Physical Review B 97, 220502(R) (2018)]. In this work, we observe unexpected van Hove singularities in the phonon density of states at energies of 1–2.5 meV. We also observe that, when the superconducting sample is cooled below the superconducting transition temperature Tc, an enhancement of the phonon density of states with energies below twice the superconducting-gap energy. Our results suggest that while the superconductivity in the In-doped (Pb0.5Sn0.5)Te sample is driven by phonons, its superconducting mechanism is beyond a simple BCS theory.

 

2018-05-17

Evidence for a Dirac nodal-line semimetal in SrAs3

 

Our group published a paper titled "Evidence for a Dirac nodal-line semimetal in SrAs3" in Science Bulletin [Li et al., Science Bulletin 63, 535 (2018)]. By carrying out magnetotransport measurements and performing first-principle calculations, we demonstrate that the topological Dirac nodal-line state has been realized in high-quality single crystals of SrAs3. We obtain the nontrivial π Berry phase by analysing the Shubnikov-de Haas quantum oscillations. We also observe a robust negative longitudinal magnetoresistance induced by the chiral anomaly. Accompanying first-principles calculations identify that a single hole pocket enclosing the loop nodes is responsible for these observation.

 

2018-02-23

Our group published a fourth paper in PRL on quantum spin liquid candidates

 

In collaboration with Prof. Jian-Xin Li's group in our department and Shiyan Li's group in Fudan University, we published a paper entitled "Spin-Glass Ground State in a Triangular-Lattice Compound YbZnGaO4" in PRL [PRL 120, 087201 (2018)]. YbMgGaO4 has attracted a lot of attention in recent years due to the possibility of realizing the exotic quantum-spin-liquid (QSL) ground state. However, by studying its sister compound YbZnGaO4 with various techniques including dc susceptibility, ultralow-temperature specific heat, inelastic neutron scattering, ultralow-temperature thermal conductivity and ac susceptibility, combined with linear spin-wave calculations, we find that the material is not a QSL, but instead a spin glass, with frozen, short-range spin-spin correlations at low temperatures. This conclusion also holds for YbMgGaO4, as confirmed by the ultralow-temperature ac susceptibility measurements. Our work provides an important lesson in identifying a QSL, as disorder-induced spin glass mimics it in many aspects. More details can be found here.

 

2018-02-10

Our group's third PRL paper on α-RuCl3

 

In collaboration with Prof. Shiyan Li's group in Fudan University, we published a paper titled "Ultralow-Temperature Thermal Conductivity of the Kitaev Honeycomb Magnet α-RuCl3 across the Field-Induced Phase Transition" in [PRL 120, 067202 (2018)]. This is our group's third PRL paper on α-RuCl3 within one year. Previously, we demonstrated that the Kitaev physics is realized in α-RuCl3 [ PRL 118, 107203 (2017)] (see also, the News), and a quantum spin liquid phase may be induced by an external magnetic field [PRL 119, 227208 (2017)] (see also, the News). In this work, we further investigate the high-field phase by performing ultralow-temperature thermal conductivity measurements on single crystals of α-RuCl3. We provide key insights into the field-induced phase and strong constrains for the theory. More details can be found here.

 

2017-12-04

Congratulations on Shichao for successfully defending his thesis !

 

Shichao successfully defended for his PhD Thesis on December 4th. His sustained efforts have been highly appreciated by the Defense Committee. He will be awarded the PhD degree soon and become the first PhD graduated from our group. Congratulations, Dr. Li! The group thank him for his great contributions and wish him a wonderful career!

 

 

2017-12-02

Our group made another important discovery in α-RuCl3

 

In collaboration with Prof. Weiqiang Yu's group in Renmin University of China, we published a paper titled "Gapless Spin Excitations in the Field-Induced Quantum Spin Liquid Phase of α-RuCl3" in [PRL 119, 227208 (2017)]. α-RuCl3 is a leading candidate to realize the Kitaev physics, as we demonstrated earlier in [ PRL 118, 107203 (2017)] (see also, the News). In this work, we combined susceptibility, specific-heat, and nuclear-magnetic-resonance measurements, showing that α-RuCl3 becomes a quantum spin liquid in a magnetic field of 7.5 T applied in the a-b plane. More details can be found here.

 

 

2017-11-27

Paper published in PRB in collaboration with Prof. Weiqiang Yu's group

 

In collaboration with Prof. Weiqiang Yu 's group in Renmin University of China, our group coauthored a paper in Physical Review B 96, 205147 (2017), reporting high-pressure magnetization and NMR studies of a proximate quantum spin liquid candidate α-RuCl3. In this work, Kejing provided the high-quality single crystals.

 

2017-09-10

Interplay between superconductivity and antiferromagnetic order in KxFe2-ySe2

 

Our group published a paper titled "Suppression of the antiferromagnetic order when approaching the superconducting state in a phase-separated crystal of KxFe2-ySe2" on PRB [Li et al., Physical Review B 96, 094503 (2017)]. In this work, we observe both the spin-wave excitations and spin resonance, resulting from the antiferromagnetic and superconducting phases, respectively. We find that well before entering the superconducting state, the development of the magnetic order is interrupted, at ∼ 42 K. We consider this result to be evidence for the physical separation of the antiferromagnetic and superconducting phases. More details can be found here.

 

2017-03-10

Our group published a paper in PRL in collaboration with Prof. Jian-Xin Li's group, reporting the finding of Kitaev physics in α-RuCl3

 

We reported the key ingredient composing Kitaev's proposal in a paper titled "Spin-Wave Excitations Evidencing the Kitaev Interaction in Single Crystalline α-RuCl3" in PRL [Ran et al., Physical Review Letters 118, 107203 (2017)]. The celebrated Kitaev quantum spin liquid was proposed theoretically in the year of 2006. This new state exhibits exotic properties in which electrons are broken into pieces, and it can find applications in quantum computation. Experimentally, such a state has not been identified so far. In our work, we have found that the behaviors of the spins in single crystals of a honeycomb-layered material RuCl3 fit Kitaev's proposal well. Our results demonstrate that the Kitaev interaction, the concept central to the proposal, has been discovered in a real material. These findings pave the way for further harnessing the material for quantum computation. More details can be found here.

2017-02-20

Paper published in Nature Communications in collaboration with Prof. Haihu Wen's group

 

In collaboration with Prof. Haihu Wen's group in our Department, our group coauthored a paper in Nature Communications 8, 14466 (2017), reporting interesting behaviors of the superconducting state in a promising candidate for topological superconductivity in SrxBi2Se3. In this work, Jinghui and Kejing provided very high-quality single crystals of SrxBi2Se3. A more detailed news report can be found here.

2016-12-24

Prof. Wen delivered a lecture on neutron sca-ttering studies on high-Tc superconductors at PLAUST

 

Prof. Wen has been invited to give a lecture at PLAUST (PLA University of Science and Technology) on Dec. 24th, introducing neutron scattering techniques and studies on high-Tc superconductors. This activity is organized by PLAUST and Jiangsu Society of Physcis, more details can be found here.

2015-06-02

Papers published as tributes to the Centenary of our Physics Department

 

Our group published a paper titled "Magnetic neutron scattering studies on the Fe-based superconductor system Fe1+yTe1-xSex" on Annals of Physics as a tribute to the centenary of our Physics Department. The Chinese version of the article was published on Acta Physics Sinica. In this paper, we present a brief overview on the interplay between magnetism and superconductivity in one of the Fe-based superconductor systems, Fe1+yTe1-xSex. We conclude that magnetism and superconductivity in this system couple to each other closely, while the static magnetic order around (0.5, 0) competes with superconductivity, the spin excitations around (0.5, 0.5) may be an important ingredient for it. We also discuss the nature of magnetism and substitution effects of 3d transition metals.

2015-01-06

Effects of 3d transition metal substitution in the Fe-based superconductors

 

Our group published a paper titled "Substitution of Ni for Fe in superconducting Fe0.98Te0.5Se0.5 depresses the normal-state conductivity but not the magnetic spectral weight" on PRB. In this work, we study the Ni-substitution effects on the electronic and magnetic properties of an Fe-based superconductor Fe0.98Te0.5Se0.5. Together with our previous paper on the Cu-doping effects [PRB 88, 144509 (2013)], we provide a complete picture on the 3d transition metal substitution effects in the Fe-based superconductors---that is, the impact is more depe ndent on the scattering potential of the substituent, and in the extreme case such as Cu, the main effect of the substitution is to localize the itinerant electrons. This conclusion also seems to be applicable to other Fe-based superconductor systems, such as 122 and 111. Jinghui has been the leading author of the paper. This is his first paper. Congratulations on him!

2014-12-24

Congratulations on Jinghui and Kejing for their scholarships!

 

Jinghui Wang and Kejing Ran have been awarded the "Excellent New Graduate Student Scholarship". Congratulations on them!

2014-10-25

PPMS installed and running

 

The physical property measurement system (PPMS) was installed at our lab and is currently running. It is using a closed-cycle system with a compressor that converts Helium gas into liquid He, and thus no liquid He supply is needed at all. The system is equipped with the options to measure the magnetization (VSM), electrical transport (ETO), thermal power and conductivity (TTO), and specific heat (HCO).

2014-03-30

Experiments in France and US

 

From Feburary 10th to 24th, Shichao conducted his first neutron scattering experiment at Laboratory of Leon Brillouin (LLB), CEA, a reactor-type neutron source at Saclay near Paris. He worked on two triple-axis spectrometers 1T and 2T.

 

During March 12th to 21st, Yuan and Jinghui performed their first neutron scattering experiment on a triple-axis spectrometer HB1 at the High Flux Isotope Reactor (HFIR) of Oak Ridge National Lab.