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Overview on the physics and materials of the new superconductor KxFe2-ySe2Sep 26 2012Since the discovery of high temperature superconductivity in iron pnictides in early 2008, many iron-based superconductors with different structures have been discovered, with the highest transition temperature to date being 57 K. By the end of 2010, ... More

Vortex-unbinding and finite-size effects in Tl2Ba2CaCu2O8 thin filmsFeb 28 2003Oct 01 2003Current-voltage ($I$-$V$) characteristics of Tl$_2$Ba$_2$CaCu$_2$O$_8$ thin films in zero magnetic field are measured and analyzed with the conventional Kosterlitz-Thouless-Berezinskii (KTB) approach, dynamic scaling approach and finite-size scaling approach, ... More

Two energy scales and close relationship between the pseudogap and superconductivity in underdoped cuprate superconductorsAug 29 2007Sep 29 2007By measuring the low temperature specific heat, the low energy quasi-particle excitation has been derived and analyzed in systematically doped La$_{2-x}$Sr$_{x}$CuO$_{4}$ single crystals. The Volovik's relation predicted for a d-wave superconductor has ... More

Multi-band effect in the noncentrosymmetric superconductors Mg_{12-δ}Ir_{19}B_{16} revealed by Hall effect and magnetoresistance measurementsJun 09 2010We report the longitudinal resistivity and Hall effect measurements on the noncentrosymmetric superconducting Mg$_{12-\delta}$Ir$_{19}$B$_{16}$ samples with different critical transition temperatures. A strong temperature dependence of the Hall coefficient ... More

Detecting Syntactic Features of Translated ChineseApr 23 2018We present a machine learning approach to distinguish texts translated to Chinese (by humans) from texts originally written in Chinese, with a focus on a wide range of syntactic features. Using Support Vector Machines (SVMs) as classifier on a genre-balanced ... More

Comparative study of vortex dynamics in CaKFe4As4 and Ba0.6K0.4Fe2As2 single crystalsDec 17 2018We investigate the vortex dynamics in two typical hole doped iron based superconductors CaKFe$_4$As$_4$ (CaK1144) and Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ (BaK122) with similar superconducting transition temperatures. It is found that the magnetization hysteresis ... More

Contrasting Pair-Breaking Effects by Doping Mn and Zn in Ba0.5K0.5Fe2As2Jan 07 2010May 05 2010Resistivity, Hall effect, magnetoresistance and DC magnetization were measured in Mn and Zn doped Ba$_{0.5}$K$_{0.5}$Fe$_{2}$As$_{2}$ samples. It is found that the Mn-doping can depress the superconducting transition temperature drastically with a rate ... More

Fishtail effect and the vortex phase diagram of single crystal Ba0.6K0.4Fe2As2Jul 24 2008Oct 10 2008By measuring the magnetization hysteresis loops of superconducting Ba0.6K0.4Fe2As2 single crystals, we obtained the high upper critical field and large current carrying ability, which point to optimistic applications. The fishtail (or second peak) effect ... More

Possible nodeless superconductivity in the noncentrosymmetric superconductor Mg_(12-delta)Ir_19B_16Aug 26 2007We measured the resistivity, diamagnetization, and low-temperature specific heat of the newly discovered noncentrosymmetric superconductor Mg_(12-delta)Ir_19B_16. The temperature dependence of specific heat is consistent with the model of an isotropic ... More

Nodeless Superconductivity in the Noncentrosymmetric Superconductor $Mg_{10}Ir_{19}B_{16}$Jun 06 2007Jun 09 2007We measured the resistivity, diamagnetization and low temperature specific heat of the newly discovered noncentrosymmetric superconductor $Mg_{10}Ir_{19}B_{16}$. It is found that the superconducting gap has an s-wave symmetry with a value of about $\Delta_0 ... More

Growth and post-annealing studies of La-Bi2201 single crystalsNov 05 2008Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ (0$\leq x \leq$1.00) single crystals with high-quality have been grown successfully using the travelling-solvent floating-zone technique. The patterns of X-ray diffraction suggest high crystalline quality of the ... More

Reversibly tuning the insulating and superconducting state in KxFe2-ySe2 crystals by post-annealingMar 07 2011Since the discovery of superconductivity at 26 K in oxy-pnictide LaFeAsO1-xFx, enormous interests have been stimulated in the field of condensed matter physics and material sciences. Among the many kind of structures in the iron pnictide superconductors, ... More

Highly anisotropic superconducting gaps and possible evidence of antiferromagnetic order in FeSe single crystalsMar 25 2017Specific heat has been measured in FeSe single crystals down to 0.414 K under magnetic fields up to 16 T. A sharp specific heat anomaly at about 8.2 K is observed and is related to the superconducting transition. Another jump of specific heat is observed ... More

Doping effect of Cu and Ni impurities on the Fe-based superconductor Ba0.6K0.4Fe2As2Apr 16 2013Copper and Nickel impurities have been doped into the iron pnictide superconductor Ba0.6K0.4Fe2As2. Resistivity measurements reveal that Cu and Ni impurities suppress superconducting transition temperature T_c with rates of \Delta T_c/Cu-1% = -3.5 K and ... More

Strong and nonmonotonic temperature dependence of Hall coefficient in superconducting K$_x$Fe$_{2-y}$Se$_2$ single crystalsJul 06 2014In-plane resistivity, magnetoresistance and Hall effect measurements have been conducted on quenched K$_x$Fe$_{2-y}$Se$_2$ single crystals in order to analysis the normal-state transport properties. It is found that the Kohler's rule is well obeyed below ... More

Nodal Superconducting Gap in $β$-FeSDec 13 2015Low temperature specific heat has been measured in superconductor $\beta$-FeS with T$_c$ = 4.55 K. It is found that the low temperature electronic specific heat C$_e$/T can be fitted to a linear relation in the low temperature region, but fails to be ... More

Superconductivity in LiOHFeS single crystals with a shrunk c-axis lattice constantDec 12 2016By using a hydrothermal ion-exchange method, we have successfully grown superconducting crystals of LiOHFeS with ${T_c}$ of about 2.8 K. Being different from the sister sample (Li${_{1-x}}$Fe${_x}$)OHFeSe, the energy dispersion spectrum analysis on LiOHFeS ... More

Vortex lattice and vortex bound states in CsFe$_2$As$_2$ investigated by scanning tunneling microscopy/spectroscopyJan 08 2018Jul 11 2018We investigate the vortex lattice and vortex bound states in CsFe$_2$As$_2$ single crystals by scanning tunneling microscopy/spectroscopy (STM/STS) under various magnetic fields. A possible structural transition or crossover of vortex lattice is observed ... More

Robust superconductivity and transport properties in (Li1-xFex)OHFeSe single crystalsJan 19 2016The recently discovered (Li${_{1-x}}$Fe${_x}$)OHFeSe superconductor with $T_c$ about 40K provides a good platform for investigating the magnetization and electrical transport properties of FeSe-based superconductors. By using a hydrothermal ion-exchange ... More

Zero-Energy Modes on Superconducting Bismuth Islands Deposited on Fe(Te,Se)May 14 2019Topological superconductivity is one of the frontier research directions in condensed matter physics. One of the unique elementary excitations in topological superconducting state is the Majorana fermion (mode) which is its own antiparticle and obeys ... More

Preliminary study on parameter estimation accuracy of supermassive black hole binary inspirals for TianQinJan 08 2019May 30 2019We use the Fisher information matrix method to calculate the parameter estimation accuracy of inspiraling supermassive black holes binaries for TianQin, a space-borne laser interferometric detector aimed at detecting gravitational waves in the millihertz ... More

Possible superconducting fluctuation and pseudogap state above $T_c$ in CsFe$_2$As$_2$Apr 25 2016Resistive, magnetization, torque, specific heat and scanning tunneling microscopy measurements are carried out on the hole heavily doped CsFe$_2$As$_2$ single crystals. A characteristic temperature $T^*\sim13$ K, which is several times higher than the ... More

Structures and Physical Properties of CsV$_2$Se$_{2-x}$O and V$_2$Se$_2$OMar 02 2018By using solid-state reactions, we successfully synthesize new oxyselenides CsV$_2$Se$_{2-x}$O (x = 0, 0.5). These compounds containing V$_2$O planar layers with a square lattice crystallize in the CeCr$_2$Si$_2$C structure with the space group of $P4/mmm$. ... More

Scrutinizing the double superconducting gaps and strong coupling pairing in (Li1-xFexOH)FeSeJun 15 2015Aug 05 2015In the iron based superconductors, one of the on-going frontier studies is about the pairing mechanism. The recent interest concerns the high temperature superconductivity and its intimate reason in the monolayer FeSe thin films. The challenge here is ... More

Sign reversal superconducting gaps revealed by phase referenced quasi-particle interference of impurity induced bound states in (Li$_{1-x}$Fe$_x$)OHFe$_{1-y}$Zn$_y$SeMar 28 2018By measuring the spatial distribution of differential conductance near impurities on Fe sites, we have obtained the quasi-particle interference (QPI) patterns in the (Li$_{1-x}$Fe$_x$)OHFe$_{1-y}$Zn$_y$Se superconductor with only electron Fermi surfaces. ... More

General theory of sending-or-not-sending twin-field quantum key distributionApr 12 2019May 06 2019The Sending-or-Not-Sending (SNS) protocol of the twin-field quantum key distribution (TF-QKD) has its advantage of unconditional security proof under any coherent attack and fault tolerance to large misalignment error even considered finite-key effect. ... More

Rigid vortices in MgB2Mar 21 2003Oct 01 2003Magnetic relaxation of high-pressure synthesized MgB$_2$ bulks with different thickness is investigated. It is found that the superconducting dia-magnetic moment depends on time in a logarithmic way; the flux-creep activation energy decreases linearly ... More

Discovery of a new nontoxic cuprate superconducting system Ga-Ba-Ca-Cu-OMay 23 2018Superconductivity is observed in a new nontoxic cuprate system Ga-Ba-Ca-Cu-O, with Tc = 82K for GaBa2Ca5Cu6O14+{\delta} (Ga-1256) and Tc = 116K probably for GaBa2Ca3Cu4O10+{\delta} (Ga-1234) or GaBa2Ca2Cu3O8+{\delta} (Ga-1223), respectively. All compounds ... More

Superconductivity induced by doping Platinum in BaFe2As2Jan 27 2010Apr 01 2010By substituting Fe with the 5d-transition metal Pt in BaFe2As2, we have successfully synthesized the superconductors BaFe2-xPtxAs2. The systematic evolution of the lattice constants indicates that the Fe ions were successfully replaced by Pt ions. By ... More

The spectroscopic signature of Kondo screening on single adatoms in Na(Fe0.96Co0.03Mn0.01)AsFeb 28 2014The electronic states of surface adatoms in Na(Fe0.96Co0.03Mn0.01)As have been studied by low temperature scanning tunneling spectroscopy. The spectra recorded on the adatoms display both superconducting coherence peaks and an asymmetric resonance in ... More

Direct Evidence of Superconductivity with Twofold Symmetry in Bi2Te3 Thin Film Deposited on FeTe0.55Se0.45Apr 25 2018Topological superconductor is a timely and frontier topic in condensed matter physics. In superconducting state, an order parameter will be established with the basic or subsidiary symmetry of the crystalline lattice. In doped Bi2Se3 with a basic threefold ... More

Multiple Magnetization Peaks and New Type of Vortex Phase Transitions in Ba0.6K0.4Fe2As2Nov 25 2011Nov 30 2011Magnetization and its relaxation have been measured on Ba0.6K0.4Fe2As2 single crystals with Tc = 39 K. The magnetization hysteresis loops (MHLs) exhibit flux jumps in the low temperature region, and a second peak-effect in the intermediate temperature ... More

Metastable superconducting state in quenched KxFe2-ySe2Jun 11 2012By direct quenching or post-annealing followed by quenching, we have successfully obtained a series of KxFe2-ySe2 samples with different properties. It is found that the samples directly quenched in the cooling process of growth show superconductivity ... More

$S$-wave pairing symmetry in non-centrosymmetric superconductor Re$_3$WJan 12 2008The alloys of non-centrosymmetric superconductor, Re$_3$W, which were reported to have an $\alpha$-Mn structure [P. Greenfield and P. A. Beck, J. Metals, N. Y. \textbf{8}, 265 (1959)] with $T_\mathrm{c}=9 $K were prepared by arc melting. The ac susceptibility ... More

Simultaneous Vanishing of the Nematic Electronic State and the Structural Orthorhombicity in NaFe$_{1-x}$Co$_x$As Single CrystalsNov 04 2014We have carried out in-plane resistivity measurements under a uniaxial pressure in NaFe$_{1-x}$Co$_x$As single crystals. A clear distinction of the in-plane resistivity $\rho_a$ and $\rho_b$ with the uniaxial pressure along $b$-axis was discovered in ... More

Strong coupling superconductivity and prominent superconducting fluctuations in the new superconductor Bi4O4S3Apr 11 2013Sep 16 2013Electric transport and scanning tunneling spectrum (STS) have been investigated on polycrystalline samples of the new superconductor Bi4O4S3. A weak insulating behavior in the resistive curve has been induced in the normal state when the superconductivity ... More

Merging Dirac electrons and correlation effect in the heterostructured Bi2Te3/Fe1+dTeSep 24 2015The topological insulator and strong electronic correlation effect are two important subjects in the frontier studies of modern condensed matter physics. A topological insulator exhibits a unique pair of surface conduction bands with the Dirac dispersion ... More

Sending-or-not twin-field quantum key distribution in practiceJul 25 2018We present results of practical sending-or-not quantum key distribution. In real-life implementations, we need consider the following three requirements, a few different intensities rather than infinite number of different intensities, a phase slice of ... More

Pressure Tuned Enhancement of Superconductivity and Change of Ground State Properties in LaO0.5F0.5BiSe2 Single CrystalsJul 22 2014By using a hydrostatic pressure, we have successfully tuned the ground state and superconductivity in LaO0.5F0.5BiSe2 single crystals. It is found that, with the increase of pressure, the original superconducting phase with Tc about 3.5 K can be tuned ... More

Intrinsic Josephson junctions in the iron-based multi-band superconductor (V2Sr4O6)Fe2As2May 22 2014In layered superconductors, Josephson junctions may be formed within the unit cell due to sufficiently low interlayer coupling. These intrinsic Josephson junction (iJJ) systems have attracted considerable interest for their application potential in quantum ... More

Upper critical field, Hall effect and magnetoresistance in the iron-based layered superconductor LaFeAsO_{0.9}F_{0.1-δ}Mar 09 2008Jul 22 2008By using a two-step method, we successfully synthesized the iron based new superconductor LaFeAsO_{0.9}F_{0.1-\delta}$. The resistive transition curves under different magnetic fields were measured, leading to the determination of the upper critical field ... More

Upper critical field, anisotropy, and superconducting properties of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystalsAug 18 2008Oct 06 2008The temperature dependent resistivity of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ (x = 0.23, 0.25, 0.28 and 0.4) single crystals and the angle dependent resistivity of superconducting Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ single crystals were measured in magnetic fields ... More

Growth and characterization of A_{1-x}K_xFe_2As_2 (A = Ba, Sr) single crystals with x=0 - 0.4Jul 05 2008Oct 18 2008Single crystals of A$_{1-x}$K$_x$Fe$_2$As$_2$ (A=Ba, Sr) with high quality have been grown successfully by FeAs self-flux method. The samples have sizes up to 4 mm with flat and shiny surfaces. The X-ray diffraction patterns suggest that they have high ... More

Synthesizing and characterization of hole doped nickel based layer superconductor (La$_{1-x}$Sr$_{x}$)ONiAsMar 27 2008Mar 29 2008We report the synthesizing and characterization of the hole doped Ni-based superconductor ($La_{1-x}Sr_{x})ONiAs$. By substituting La with Sr, the superconducting transition temperature $T_c$ is increased from 2.75 K of the parent phase $LaONiAs$ to 3.7 ... More

Point-Contact Spectroscopy of Iron-Based Layered Superconductor LaO$_{0.9}$F$_{0.1-δ}$FeAsMar 17 2008Aug 07 2008We present point-contact spectroscopy data for junctions between a normal metal and the newly discovered F-doped superconductor LaO$_{0.9}$F$_{0.1-\delta}$FeAs (F-LaOFeAs). A zero-bias conductance peak was observed and its shape and magnitude suggests ... More

Nodeless superconductivity in K$_x$Fe$_{2-y}$Se$_2$ single crystals revealed by low temperature specific heatJan 26 2011Low temperature specific heat (SH) has been measured in K$_x$Fe$_{2-y}$Se$_2$ single crystals with T$_c$ = 32 K. The SH anomaly associated with the superconducting transition is moderate and sharp yielding a value of $\Delta C/T \mid_{T_c}$ = 11.6 $\pm$ ... More

Discrete energy levels of Caroli-de Gennes-Martricon states in quantum limit due to small Fermi energy in FeTe$_{0.55}$Se$_{0.45}$Sep 27 2017Caroli-de Gennes-Martricon (CdGM) states were predicted in 1964 as low energy excitations within vortex cores of type-II superconductors. In the quantum limit, namely $T/T_\mathrm{c} \ll \Delta/E_\mathrm{F}$, the energy levels of these states were predicted ... More

Magnetism and superconductivity in Sr$_2$VFeAsO$_3$ revealed by $^{75}$As- and $^{51}$V-NMR under elevated pressuresMay 13 2014We report $^{75}$As- and $^{51}$V-nuclear magnetic resonance (NMR) measurements on the iron-based superconductor Sr$_2$VFeAsO$_3$ with alternating stacks structure. We find that the $^{75}$As nuclear spin-spin relaxation rate ($1/T_2$) shows a pronounced ... More

BCS-like critical fluctuations with limited overlap of Cooper pairs in FeSeApr 28 2017Jul 14 2017In conventional superconductors, very narrow superconducting fluctuation regions are observed above $T_c$ because of the strong overlapping of Cooper pairs in a coherence volume. In the bulk form of iron chalcogenide superconductor FeSe, it is argued ... More

Synthesis, structural and transport properties of the hole-doped Superconductor Pr_{1-x}Sr_xFeAsOOct 06 2008Jan 13 2009Superconductivity was achieved in PrFeAsO by partially substituting Pr^{3+} with Sr^{2+}. The electrical transport properties and structure of this new superconductor Pr_{1-x}Sr_xFeAsO at different doping levels (x = 0.05$\sim$ 0.25) were investigated ... More

Multi-Band Exotic Superconductivity in the New Superconductor Bi4O4S3Jul 20 2012Resistivity, Hall effect and magnetization have been investigated on the new superconductor Bi4O4S3. A weak insulating behavior has been induced in the normal state when the superconductivity is suppressed. Hall effect measurements illustrate clearly ... More

Hall effect and magnetoresistance in single crystals of NdFeAsO$_{1-x}$F$_{x}$Jun 10 2008Sep 09 2008Hall effect and magnetoresistance have been measured on single crystals of $NdFeAsO_{1-x}F_{x}$ with x = 0 ($T_c$ = 0 $ $K) and x = 0.18 ($T_c$ = 50 $ $K). For the undoped samples, strong Hall effect and magnetoresistance with strong temperature dependence ... More

Collective vortex pinning and crossover between second order to first order transition in optimally doped Ba1-xKxBiO3 single crystalsJan 05 2017Measurements on magnetization and relaxation have been carried out on an optimally doped Ba$_{0.59}$K$_{0.47}$BiO$_{3+\delta}$ single crystal with $T_c$ = 31.3 K. Detailed analysis is undertaken on the data. Both the dynamical relaxation and conventional ... More

The finite size effect of asymmetric sending or not sending twin-field quantum key distribution with two-way communicationAug 15 2019The Sending-or-Not-Sending (SNS) protocol of the twin-field quantum key distribution (TF-QKD) has its advantage of unconditional security proof under any coherent attack and fault tolerance to large misalignment error, and has attracted a lot attentions. ... More

Doping Dependence of Superconductivity and Lattice Constants in Hole Doped $La_{1-x}Sr_xFeAsO$Jun 12 2008Jun 12 2008By using solid state reaction method we have fabricated the hole doped $La_{1-x}Sr_xFeAsO$ superconductors with Sr content up to 0.13. It is found that the sharp anomaly at about 150 K and the low temperature upturn of resistivity are suppressed by doping ... More

Nodal Superconductivity with Multiple Gaps in SmFeAsO$_{0.9}$F$_{0.1}$Jun 12 2008Aug 07 2008We report the observation of two gaps in the superconductor SmFeAsO$_{0.9}$F$_{0.1}$ (F-SmFeAsO) with $T_c=51.5K$ as measured by point-contact spectroscopy. Both gaps decrease with temperature and vanish at $T_c$ and the temperature dependence of the ... More

Hall effect and magnetoresistance in the normal state of the superconductor LaO$_{0.9}$F$_{0.1-x}$FeAsMar 05 2008Mar 28 2008By using a two-step method, we successfully synthesized the iron based new superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs. The Hall effect and magnetoresistance were measured in wide temperature region. A negative Hall coefficient R_H has been found implying ... More

Bulk Evidence for d-Wave Pairing Symmetry in NCCO Detected by Specific HeatSep 17 2002Feb 24 2005This file has been withdrawn

Superconductivity induced by doping Pd in SrFe2-xPdxAs2Mar 02 2009Mar 05 2009By using solid state reaction method, we have synthesized the Pd-doped superconductor SrFe2-xPdxAs2. The systematic evolution of the lattice constants indicated that the Fe ions were successfully replaced by the Pd. By increasing the doping content of ... More

High-T_c superconductivity induced by doping rare earth elements into CaFeAsFDec 05 2008We have successfully synthesized the fluoride-arsenide compounds Ca$_{1-x}$RE$_x$FeAsF (RE=Nd, Pr; x=0, 0.6). The x-ray powder diffraction confirmed that the main phases of our samples are Ca$_{1-x}$RE$_x$FeAsF with the ZrCuSiAs structure. By measuring ... More

Impurity effect and suppression to superconductivity in Na(Fe$_{0.97-x}$Co$_{0.03}$T$_x$)As (T=Cu, Mn)Aug 06 2013We report the successful growth and the impurity scattering effect of single crystals of Na(Fe$_{0.97-x}$Co$_{0.03}$T$_x$)As (T=Cu, Mn). The temperature dependence of DC magnetization at high magnetic fields is measured for different concentrations of ... More

Superconductivity Appears in the Vicinity of an Insulating-Like Behavior in CeO$_{1-x}$F$_{x}$BiS$_{2}$Aug 24 2012Resistive and magnetization properties have been measured in BiS$_2$-based samples CeO$_{1-x}$F$_{x}$BiS$_{2}$ with a systematic substitution of O with F (0 $<$ x $<$ 0.6). In contrast to the band structure calculations, it is found that the parent phase ... More

Inherent Relation between Nernst Signal and Nodal Quasiparticle Transport in Pseudogap Region of Underdoped High Temperature SuperconductorsOct 01 2004Oct 03 2004In-plane Nernst signal and resistivity have been measured for three $La_{2-x}Sr_xCuO_4$ single crystals (x=0.09, 0.11 and 0.145) with the magnetic field parallel to c-axis. A quadratic temperature dependence of resistivity, i.e., $\rho=\rho_0+aT^2$ is ... More

Universality and unconventional enhancement of flux-flow resistivity in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$Dec 06 2016Measurements of the current-voltage characteristics were performed on Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals with doping level $0.044 \leq x \leq 0.1$. An unconventional increase in the flux-flow resistivity $\rho_{\rm ff}$ with decreasing magnetic ... More

Path of Vowel Raising in Chengdu Dialect of MandarinMar 11 2018He and Rao (2013) reported a raising phenomenon of /a/ in /Xan/ (X being a consonant or a vowel) in Chengdu dialect of Mandarin, i.e. /a/ is realized as [epsilon] for young speakers but [ae] for older speakers, but they offered no acoustic analysis. We ... More

Superconductivity at 22.3 K in SrFe2-xIrxAs2Feb 23 2009Feb 24 2009By substituting the Fe with the 5d-transition metal Ir in SrFe2As2, we have successfully synthesized the superconductor SrFe2-xIrxAs2 with Tc = 22.3 K at x = 0.5. X-ray diffraction indicates that the material has formed the ThCr2Si2-type structure with ... More

Low temperature specific heat of the 12442-type KCa_2Fe_4As_4F_2 single crystalsMar 22 2019Low-temperature specific heat (SH) is measured on the 12442-type KCa_2Fe_4As_4F_2 single crystal under different magnetic fields. A clear SH jump with the height \Delta C/T|_{T_c} = 130 mJ/mol K^2 was observed at the superconducting transition temperature ... More

Experimental Demonstration of the Sign Reversal of the Order Parameter in (Li1-xFex)OHFe1-yZnySeApr 20 2017Iron pnictides are the only known family of unconventional high-temperature superconductors besides cuprates. Until recently, it was widely accepted that superconductivity is spin-fluctuation driven and intimately related to their fermiology, specifically, ... More

Physical properties of noncentrosymmetric superconductor Ru$_7$B$_3$Nov 14 2008Nov 17 2008Transition metal boride Ru$_7$B$_3$ was found to be a noncentrosymmetric superconductor with $T_{C}$ equal to 3.3 K. Superconducting and normal state properties of Ru$_7$B$_3$ were determined by a self-consistent analysis through resistivity($\rho_{xx}$ ... More

Linear Temperature Dependence of the Lower Critical Field $H_{c1}$ in F-Doped LaOFeAs SuperconductorsApr 10 2008We present the first experimental results of the lower critical field $H_{c1}$ of the newly discovered F-doped superconductor LaO$_{0.9}$F$_{0.1}$FeAs (F-LaOFeAs) by global and local magnetization measurements. It is found that $H_{c1}$ showed an clear ... More

Low Temperature Specific Heat of Optimally Doped BaFe$_{2-x}$$TM_x$As$_{2}$ ($TM$ = Co and Ni) Single Crystals: Constraint on the Pairing GapJun 14 2010Low temperature specific heat has been measured in optimally doped and highly overdoped non-superconducting BaFe$_{2-x}$TM$_x$As$_{2}$ ($TM$ = Co and Ni) single crystals. By using the data of the overdoped samples, we successfully removed the phonon contribution ... More

Anomalous Meissner effect in pnictide superconductorsOct 22 2010The Meissner effect has been studied in Ba(Fe0.926Co0.074)2As2 and Ba0.6K0.4Fe2As2 single crystals and compared to well known, type-II superconductors LuNi2B2C and V3Si. Whereas flux penetration is mostly determined by the bulk pinning (and, perhaps, ... More

Raman-Scattering Detection of Nearly Degenerate $s$-Wave and $d$-Wave Pairing Channels in Iron-Based Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ and Rb$_{0.8}$Fe$_{1.6}$Se$_2$ SuperconductorsAug 24 2012Jul 27 2015We show that electronic Raman scattering affords a window into the essential properties of the pairing potential $V_{\mathbf{k},\mathbf{k^{\prime}}}$ of iron-based superconductors. In Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ we observe band dependent energy gaps ... More

Superconducting fluctuations in the reversible magnetization of the iron-pnictide $Ba_{1-x}K_xFe_2As_2$Feb 07 2009Jul 29 2009We report on isofield magnetization curves obtained as a function of temperature in two single crystals of $Ba_{1-x}K_xFe_2As_2$ with superconducting transition temperature $T_c$=28K and 32.7 K. Results obtained for fields above 20 kOe show a well defined ... More

Transport properties, upper critical field and anisotropy of Ba(Fe$_{0.75}$Ru$_{0.25}$)$_2$As$_2$ single crystalsMar 30 2012The temperature and angle dependent resistivity of Ba(Fe$_{0.75}$Ru$_{0.25}$)$_2$As$_2$ single crystals were measured in magnetic fields up to 14 T. The temperature dependent resistivity with the magnetic field aligned parallel to c-axis and ab-planes ... More

In-Gap Quasiparticle Excitations Induced by Non-Magnetic Cu Impurities in Na(Fe0.96Co0.03Cu0.01)As Revealed by Scanning Tunneling SpectroscopyJun 09 2013Nov 20 2013The pairing mechanism in the iron pnictides remains unresolved yet. One of the central issues is the structure of the superconducting order parameter which classifies the community into two different and highly disputed camps. On one hand the picture ... More

Critical current oscillations in the intrinsic hybrid vortex state of SmFeAs(O,F)Oct 28 2014In layered superconductors the order parameter may be modulated within the unit cell, leading to non-trivial modifications of the vortex core if the interlayer coherence length $\xi_c(T)$ is comparable to the interlayer distance. In the iron-pnictide ... More

Superconductivity at 36 K in Gadolinium-arsenide Oxides GdO$_{1-x}$F$_{x}$FeAsApr 05 2008Apr 08 2008In this paper we report the fabrication and superconducting properties of GdO$_{1-x}$F$_{x}$FeAs. It is found that when x is equal to 0.17, GdO$_{0.83}$F$_{0.17}$FeAs is a superconductor with the onset transition temperature T$_{c}^{on}\approx$ 36.6K. ... More

Plastic pinning replaces collective pinning as the second magnetization peak disappears in the pnictide superconductor Ba-KFe$_2$As$_2$Jan 15 2018We report a detailed study of isofield magnetic relaxation and isothermal magnetization measurements with $H$$\parallel$c on an underdoped Ba$_{0.75}$K$_{0.25}$Fe$_2$As$_2$ pnictide single crystal, with superconducting transition temperature $T_c$ = 28 ... More

Specific-Heat Measurement of Residual Superconductivity in the Normal State of Underdoped Cuprate SuperconductorsJul 03 2009We have measured the magnetic field and temperature dependence of specific heat on $Bi_2Sr_{2-x}La_xCuO_{6+\delta}$ single crystals in wide doping and temperature regions. The superconductivity related specific heat coefficient $\gamma_{sc}$ and entropy ... More

Unexpected Giant Superconducting Fluctuation and Anomalous Semiconducting Normal State in NdO1-xFxBi1-yS2 Single CrystalsOct 01 2013The BiS2-based superconductors were discovered recently. The superconductivity has been proved by many other groups. Since the previous experiments were all done on polycrystalline samples, therefore there remains a concern whether the superconductivity ... More

Critical Fields and Anisotropy of NdO0.82F0.18FeAs Single CrystalsJun 03 2008The newly discovered iron-based superconductors have stimulated enormous interests in the field of superconductivity. Since the new superconductor is a layered system, the anisotropy is a parameter with the first priority to know. Meanwhile any relevant ... More

Electronic specific heat and low energy quasiparticle excitations in superconducting state of $La_{2-x}Sr_xCuO_4$ single crystalsJun 30 2004Low temperature specific heat has been measured and extensively analyzed on a series of $La_{2-x}Sr_xCuO_4$ single crystals from underdoped to overdoped regime. From these data the quasiparticle density of states (DOS) in the mixed state is derived and ... More

Quantum Coherence in a Quantum Heat EngineJan 07 2019Jan 29 2019We identify that quantum coherence is a valuable resource in the quantum heat engine, which is designed in a quantum thermodynamic cycle assisted by a quantum Maxwell's demon. This demon is in a superposed state. The quantum work and heat are redefined ... More

Learning Intrinsic Sparse Structures within Long Short-Term MemorySep 15 2017Feb 11 2018Model compression is significant for the wide adoption of Recurrent Neural Networks (RNNs) in both user devices possessing limited resources and business clusters requiring quick responses to large-scale service requests. This work aims to learn structurally-sparse ... More

Directly visualizing the sign change of d-wave superconducting gap in Bi2Sr2CaCu2O8+δ by phase-referenced quasiparticle interferenceAug 19 2018The superconducting state is achieved by the condensation of Cooper pairs and is protected by the superconducting gap. The pairing interaction between the two electrons of a Cooper pair determines the superconducting gap function. Thus, it is very pivotal ... More

Drive the Dirac Electrons into Cooper Pairs in SrxBi2Se3Apr 27 2016Topological superconductor is a very interesting and frontier topic in condensed matter physics1. Despite the tremendous efforts in exploring the topological superconductivity, its presence is however still under heavy debates. The Dirac electrons are ... More

Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate SuperconductorsAug 22 2005Through the measurements of magnetic field dependence of specific heat in $La_{2-x}Sr_xCuO_4$ in zero temperature limit, we determined the nodal slope $v_\Delta$ of the quasiparticle gap. It is found that $v_\Delta$ has a very similar doping dependence ... More

Pseudogap, Superconducting Gap, and Fermi Arcs in Underdoped Cuprate SuperconductorsFeb 16 2005Through the measurements of magnetic field dependence of specific heat in $La_{2-x}Sr_xCuO_4$ in zero temperature limit, we find that the nodal slope $v_\Delta$ of the superconducting gap has a very similar doping dependence of the pseudogap temperature ... More

Relationship between critical current and flux-flow resistivity in the mixed state of Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$Jun 02 2017We studied the temperature and magnetic field dependence of vortex dissipation and critical current in the mixed-state of unconventional superconducting alloys Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ ($0.044 \leq x \leq 0.100$) through current-voltage measurements. ... More

Three dimensional spider-web-like superconducting filamentary paths in $K_xFe_{2-y}Se_2$ single crystalsJan 12 2013Since the discovery of high temperature superconductivity in F-doped LaFeAsO, many new iron based superconductors with different structures have been fabricated2. The observation of superconductivity at about 32 K in KxFe2-ySe2 with the iso-structure ... More

Sets of uniqueness, weakly sufficient sets and sampling sets for weighted spaces of holomorphic functions in the unit ballApr 24 2019We consider inductive limits of weighted spaces of holomorphic functions in the unit ball of $\mathbb C^n$. The relationship between sets of uniqueness, weakly sufficient sets and sampling sets in these spaces is studied. In particular, the equivalence ... More

Multi-band superconductivity and possible nodal gap in RbCr$_{3}$As$_{3}$ revealed by Andreev reflection and single-particle tunneling measurementsJan 24 2019By measuring point-contact Andreev reflection spectra in the newly discovered chromium-based quasi-one-dimensional superconductor RbCr$_{3}$As$_{3}$, we find clear evidence of two superconducting components, one has a gap value of about 1.8 meV and another ... More

Insights into the Unusual Semiconducting Behavior in Low-Dimensional BoronOct 31 2018Elementary semiconductors are rare and attractive, especially for low-dimensional materials. Unfortunately, most of boron nanostructures were found to be metallic, despite of their typical semiconducting bulk structure. Herein, we propose a general recipe ... More

Unexpected weak spatial variation of local density of sates induced by individual Co impurity atoms in Na(Fe{1-x}Cox)As as revealed by scanning tunneling spectroscopyMar 14 2012Dec 26 2012We use spatially resolved scanning tunneling spectroscopy in Na(Fe{1-x}Cox)As to investigate the impurity effect induced by Co dopants. The Co impurities are successfully identified, and the spatial distributions of local density of state at different ... More

Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$Jun 09 2014The in-plane London penetration depth, $\Delta\lambda(T)$, was measured using a tunnel diode resonator technique in single crystals of Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ with doping levels $x$ ranging from heavily underdoped, $x$=0.16 ($T_{c}$=7~K) to ... More

A tunable hybrid qubit in a triple quantum dotJun 12 2017We experimentally demonstrate quantum coherent dynamics of a triple-dot-based multi-electron hybrid qubit. Pulsed experiments show that this system can be conveniently initialized, controlled, and measured electrically, and has good coherence time as ... More

Science with TianQin: Preliminary Results on Massive Black Hole BinariesFeb 12 2019We investigate the prospects of detecting gravitational waves from coalescing massive black hole binaries in the Universe with the TianQin observatory, a space-based gravitational wave interferometer proposed to be launched in the 2030s. To frame the ... More

Power Law Like Correlation between Condensation Energy and Superconducting Transition Temperatures in Iron Pnictide/Chalcogenide Superconductors: Beyond the BCS UnderstandingFeb 27 2014Superconducting condensation energy $U_0^{int}$ has been determined by integrating the electronic entropy in various iron pnictide/chalcogenide superconducting systems. It is found that $U_0^{int}\propto T_c^n$ with $n$ = 3 to 4, which is in sharp contrast ... More

Gap Anisotropy in Iron-Based Superconductors: A Point-Contact Andreev Reflection Study of BaFe$_{2-x}$Ni$_{x}$As$_2$ Single CrystalsJun 15 2011Nov 11 2011We report a systematic investigation on c-axis point-contact Andreev reflection (PCAR) in BaFe$_{2-x}$Ni$_x$As$_2$ superconducting single crystals from underdoped to overdoped regions (0.075 $\leq x\leq 0.15$). At optimal doping ($x=0.1$) the PCAR spectrum ... More