A5045731182- Iron-based superconductors research
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
- Corporate Taxation and Avoidance
- Theoretical and Computational Physics
- Magnetic properties of thin films
- Inorganic Chemistry and Materials
- Topological Materials and Phenomena
- Quantum many-body systems
- Multiferroics and related materials
- Magnetic Properties of Alloys
- Nuclear materials and radiation effects
- Advanced Materials Characterization Techniques
State Key Laboratory of Surface Physics
2016-2025
Fudan University
2016-2025
ShangHai JiAi Genetics & IVF Institute
2021-2023
FeSe exhibits a novel ground state in which superconductivity coexists with nematic order the absence of any long-range magnetic order. Here, we report on an angle-resolved photoemission study superconducting gap structure FeSe_{0.93}S_{0.07}, without complications caused by Fermi surface reconstruction induced We find that shows pronounced twofold anisotropy around elliptical hole pocket near Z (0, 0, π), minima at end points its major axis, while no detectable is observed Γ 0) and zone...
Quantum spin liquids (QSLs) are exotic states of matter characterized by emergent gauge structures and fractionalized elementary excitations. The recently discovered triangular lattice antiferromagnet YbMgGaO$_4$ is a promising QSL candidate, the nature its ground state still under debate. Here, we use neutron scattering to study excitations in various magnetic fields. Our data reveal dispersive excitation continuum with clear upper lower edges weak field ($H=2.5$ T). Moreover, spectral...
The recently discovered kagome metal $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ ($A=\mathrm{K}$, Rb, Cs) with intertwined superconductivity and charge density wave (CDW) order has attracted considerable interest. Here we investigate the evolution of CDW in $\mathrm{Cs}{({\mathrm{V}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x})}_{3}{\mathrm{Sb}}_{5}$, where chromium substitution for vanadium introduces extra electron carriers. Our experiments reveal that is gradually suppressed under doping, which can be...
Static stripe order is detrimental to superconductivity. Yet, it has been proposed that transverse fluctuations may enhance the inter-stripe Josephson coupling and thus promote Direct experimental studies of dynamics, however, remain difficult. From a strong-coupling perspective, are realized in form dynamic "kinks"-sideways shifting sections. Here, we show how modest uniaxial pressure tuning reorganizes directional kink alignment. Our starting point La1.88Sr0.12CuO4 where ordering results...
Elucidating spin correlations in the parent compounds of high-temperature superconductors is crucial for understanding superconductivity. We used neutron scattering to study Li_{1-x}Fe_{x}ODFeSe, an insulating material with reduced electron carriers compared its superconducting counterpart (T_{c}=41 K), serving as undoped compound. Our findings show a total fluctuating moment this insulator relative FeSe and 122 iron pnictides, likely due increased interlayer distances from intercalation,...
Heavily electron-doped iron-selenide (HEDIS) high-transition-temperature (high-$T_{\rm{c}}$) superconductors, which have no hole Fermi pockets, but a notably high $T_{\rm{c}}$, challenged the prevailing $s$$_\pm$ pairing scenario originally proposed for iron pnictides containing both electron and pockets. The microscopic mechanism underlying enhanced superconductivity in HEDIS remains unclear. Here, we used neutron scattering to study spin excitations of material Li$_{0.8}$Fe$_{0.2}$ODFeSe...
The rare-earth triangular-lattice chalcogenide is a great platform for exploring both spin liquids and novel magnetic orders with anisotropic interactions frustrations. Here, we report the thermodynamic neutron-scattering measurements of ${\mathrm{KErSe}}_{2}$, using single-crystal samples. Our experiments revealed long-range stripe order below 0.2 K. Although was three dimensional, excitations exhibited negligible modulation along $z$ direction, indicating very weak interlayer coupling....
Emerging as a platform for novel quantum effects, triangular-lattice rare-earth delafossite compounds have attracted significant attention. This study investigates KTmSe${}_{2}$ using thermodynamic and neutron scattering methods, revealing highly dispersive crystal electric field excitations. From the transverse Ising model full scheme, findings uncover strong interplay between spin exchange interactions effects. These insights will provide valuable framework understanding low-temperature...
The pursuit of discovering new high-temperature superconductors that diverge from the copper-based paradigm carries profound implications for elucidating mechanisms behind superconductivity and may also enable applications. Here, our investigation reveals application pressure effectively suppresses spin charge order in trilayer nickelate La$_4$Ni$_3$O$_{10}$ single crystals, leading to emergence with a maximum critical temperature (Tc) around 30 K. In normal state, we observe "strange metal"...
The structurally simplest high-temperature superconductor FeSe exhibits an intriguing superconducting nematic paramagnetic phase with unusual spin excitation spectra that are different from typical waves; thus, determining its effective magnetic exchange interactions is challenging. Here we report neutron scattering measurements of fluctuations in the tetragonal phase. We show equal-time structure factor, $\mathcal{S}(\mathbf{Q})$, can be effectively modeled using self-consistent Gaussian...
We report neutron scattering measurements of the spinel oxide LiGaCr_{4}O_{8}, in which magnetic ions Cr^{3+} form a breathing pyrochlore lattice. Our experiments reveal coexistence nearly dispersionless resonance mode and dispersive spin-wave excitations magnetically ordered state, can be quantitatively described by quantum spin model hexagonal loops linear theory with same set exchange parameters, respectively. Comparison to other Cr oxides reveals relationship between energy lattice...
High-resolution time- and angle-resolved photoemission measurements were made on FeSe superconductors. With ultrafast photoexcitation, two critical excitation fluences that correspond to electronic phase transitions found only in the $d_{yz}$-orbit-derived band near Brillouin-zone center within our time energy resolution. Upon comparison detailed temperature dependent measurements, we conclude there are equilibrium (at approximately 90 120 K) above superconducting transition temperature, an...
We have successfully synthesized a triangular lattice magnet, ${\mathrm{NaTmTe}}_{2}$, and conducted thermodynamic inelastic neutron scattering (INS) investigations using single-crystal samples. Our magnetic susceptibility $\ensuremath{\chi}(T)$ measurements indicate antiferromagnetic interactions between ${\mathrm{Tm}}^{3+}$ moments. In our INS experiments, we observe series of dispersive crystal electric field (CEF) excitations. These dispersions could be attributed to quantum tunneling...
We apply high resolution scanning tunneling microscopy to study intrinsic defect states of bulk FeSe. Four types defects including the type I dumbbell, II top-layer Se vacancy and inner-layer Se-site are extensively analyzed by spectroscopy. From characterized depression enhancement density measured in a large energy range, dumbbell determined be Fe Se$_\mathrm{Fe}$ defect, respectively. The possible also spectroscopy analysis. determination compared largely confirmed annular dark-field...
We report high-resolution neutron scattering measurements of the low energy spin fluctuations KFe$_{2}$As$_{2}$, end member hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$ family with only hole pockets, above and below its superconducting transition temperature $T_c$ ($\sim$ 3.5 K). Our data reveals clear at incommensurate wave vector ($0.5\pm\delta$, 0, $L$), ($\delta$ = 0.2)(1-Fe unit cell), which exhibit $L$-modulation peaking $L=0.5$. Upon cooling to state, gradually open a spin-gap form sharp...
We report neutron scattering measurements of single-crystalline YFe$_2$Ge$_2$ in the normal state, which has same crystal structure to 122 family iron pnictide superconductors. does not exhibit long range magnetic order, but exhibits strong spin fluctuations. Like pnictides, displays anisotropic stripe-type antiferromagnetic fluctuations at ($\pi$, $0$, $\pi$). More interesting, however, is observation in-plane ferromagnetic wavevector ($0$, These are isotropic ($H$, $K$) plane, whose...
The nano-superconducting quantum interference device (SQUID) is considered one of the most sensitive magnetic sensors for characterization mesoscopic and microscopic moments. Therefore, it suitable measuring Meissner effect in small superconductors that cannot generate large enough signals commercial magnetometers. To achieve an optimized coupling, sample usually placed directly on a SQUID chip as close to washer possible. working temperature range nano-SQUID desirable measure wider samples....
Here, by conducting a systematic $^{89}$Y NMR study, we explore the nature of magnetic ground state in newly discovered iron-based superconductor YFe$_2$Ge$_2$. An incoherent-to-coherent crossover due to Hund's coupling induced electronic correlation is revealed below temperature $T^*\sim 75\pm15\,\mathrm{K}$. During crossover, both Knight shift ($K$) and bulk susceptibility ($\chi$) exhibit similar nonmonotonic dependence, so-called anomaly also careful $K$-$\chi$ analysis. Such an has been...
Abstract Multiple ordered states have been observed in unconventional superconductors. Here, we apply scanning tunneling microscopy to probe the intrinsic FeSe, structurally simplest iron-based superconductor. Besides well-known nematic order along [100] direction, observe a checkerboard charge iron lattice, which name [110] electronic FeSe. The is robust at 77 K, accompanied with rather weak order. At 4.5 enhanced, while forms domains reduced correlation length. In addition, collective...
High-resolution angle-resolved photoemission measurements were taken on FeSe$_{1-x}$S$_x$ (x=0, 0.04, and 0.08) superconductors. With an ultrahigh energy resolution of 0.4 meV, unusual two hole bands near the Brillouin-zone center, which was possibly a result additional symmetry breaking, identified in all sulfur-substituted samples. In addition, both highly anisotropic superconducting gaps with limited nodes evidenced. We find that larger gap outer band is reduced linearly to nematic...
The discovery of pressure-induced superconductivity in helimagnets (CrAs, MnP) has attracted considerable interest understanding the relationship between complex magnetism and unconventional superconductivity. However, nature magnetic interactions that drive unusual double-helical order these materials remains unclear. Here, we report neutron scattering measurements excitations CrAs single crystals at ambient pressure. Our experiments reveal well defined spin wave up to about 150 meV with a...