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Results for "X. G. Luo"

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Effect of iron-doping on spin-state transition and ferromagnetism in Pr$_{0.5}$Ca$_{0.5}$CoO$_{3-δ}$ cobalt oxidesSep 21 2005Resistivity and dc magnetization measurements were performed for the polycrystalline Pr$_{0.5}$Ca$_{0.5}$Co$_{1-x}$Fe$_{x}$O$_{3-\delta}$ ($x$ = 0, 0.05, 0.10 and 0.15) samples. The as-fabricated samples exhibit ferromagnetic (FM) transition and the transition ... More
Comment on "Time-Dependent Density-Matrix Renormalization Group: A Systematic Method for the Study of Quantum Many-Body Out-of- Equilibrium Systems"Dec 24 2002In a recent Letter [Phys. Rev. Lett. 88, 256403(2002), cond-mat/0109158] Cazalilla and Marston proposed a time-dependent density- matrix renormalization group (TdDMRG) algorithm for the accurate evaluation of out-of-equilibrium properties of quantum many-body ... More
In-plane ferromagnetism in charge-ordering $Na_{0.55}CoO_2$Dec 20 2005The magnetic and transport properties are systematically studied on the single crystal $Na_{0.55}CoO_2$ with charge ordering and divergency in resistivity below 50 K. A long-range ferromagnetic ordering is observed in susceptibility below 20 K with the ... More
Giant isotope effect and spin state transition induced by oxygen isotope exchange in ($Pr_{1-x}Sm_x)_{0.7}Ca_{0.3}CoO_3$Mar 28 2006Apr 30 2006We systematically investigate effect of oxygen isotope in $(Pr_{1-x}Sm_x)_{0.7}Ca_{0.3}CoO_3$ which shows a crossover with x from ferromagnetic metal to the insulator with spin-state transition. A striking feature is that effect of oxygen isotope on the ... More
Novel dynamical effects and glassy response in strongly correlated electronic systemMar 25 2007We find an unconventional nucleation of low temperature paramagnetic metal (PMM) phase with monoclinic structure from the matrix of high-temperature antiferromagnetic insulator (AFI) phase with tetragonal structure in strongly correlated electronic system ... More
Dimensional crossover and anomalous magnetoresistivity in single crystals $Na_xCoO_2$Nov 02 2004The in-plane ($\rho_{ab}$) and c-axis ($\rho_c$) resistivities, and the magnetoresistivity of single crystals $Na_xCoO_2$ with x = 0.7, 0.5 and 0.3 were studied systematically. $\rho_{ab}(T)$ shows similar temperature dependence between $Na_{0.3}CoO_2$ ... More
Energy Dependence of High Moments for Net-proton DistributionsJan 18 2010Jan 23 2010High moments of multiplicity distributions of conserved quantities are predicted to be sensitive to critical fluctuations. To understand the effect of the complicated non-critical physics backgrounds on the proposed observable, we have studied various ... More
Oxygen Isotope Effect on the Spin State Transition in (Pr$_{0.7}$Sm$_{0.3}$)$_{0.7}$Ca$_{0.3}$CoO${_3}$Oct 19 2005Oxygen isotope substitution is performed in the perovskite cobalt oxide (Pr$_{0.7}$Sm$_{0.3}$)$_{0.7}$Ca$_{0.3}$CoO${_3}$ which shows a sharp spin state transition from the intermediate spin (IS) state to the low spin (LS) state at a certain temperature. ... More
Infrared spectroscopy of the charge ordering transition in Na$_{0.5}$CoO$_2$May 11 2004We report infrared spectra of a Na$_{0.5}$CoO$_2$ single crystal which exhibits a sharp metal-insulator transition near 50 K due to the formation of charge ordering. In comparison with x=0.7 and 0.85 compounds, we found that the spectral weight associated ... More
Influence of doping level on the Hall coefficient and on the thermoelectric power in $Nd_{2-x}Ce_xCuO_4$Jun 25 2005Oct 20 2005Hall coefficient $R_H$ and thermoelectric power TEP are studied systematically in the single crystals $Nd_{2-x}Ce_xCuO_{4+\delta}$ (NCCO) with different x from underdoped to overdoped regime. With increasing doping level, both $R_H$ and TEP decrease and ... More
Transport properties in Cu$_{x}$TiSe$_{2}$ (0.015$\leq$x$\leq$0.110) Single CrystalMar 25 2007Transport properties are systematically studied for the single crystals Cu$_{x}$TiSe$_{2}$ (0.015$\leq$x$\leq$0.110). Both of in-plane and out-of-plane resistivity show the coexistence of superconducting transition and charge density wave (CDW) for the ... More
Two-Dimensional Node-Line Semimetals in a Honeycomb-Kagome LatticeMar 15 2016Recently, the concept of topological insulators has been generalized to topological semimetals, including three-dimensional (3D) Weyl semimetals, 3D Dirac semimetals, and 3D node-line semimetals. In particular, several compounds (e.g., certain three-dimensional ... More
Structural and Magnetic Properties of the Layered Manganese Oxychalcogenides:(LaO)$_2$Mn$_2$Se$_2$O and (BaF)$_2$Mn$_2$Se$_2$ONov 28 2010Apr 01 2011The new layered manganese oxychalcogenides (LaO)$_2$Mn$_2$Se$_2$O and (BaF)$_2$Mn$_2$Se$_2$O, isostructural to (LaO)$_2$Fe$_2$Se$_2$O, were synthesized by using solid state reaction. The single crystals of former compound were also successfully grown ... More
Magnetic and Transport Properties in $CoSr_2Y_{1-x}Ca_xCu_2O_7$ ($x$=0$\sim$0.4)Aug 04 2004Magnetic and transport properties of $Co Sr_2 Y_{1-x} Ca_x Cu_2 O_7$ ($x=0 \sim 0.4$) system have been investigated. A broad maximum in M(T) curve, indicative of low-dimensional antiferromagnetic ordering originated from $CoO_{1+\delta}$ layers, is observed ... More
Intergrowth and thermoelectric properties in the Bi-Ca-Co-O systemJul 17 2007Single crystals of the Bi-Ca-Co-O system have been grown using the flux method with cooling from 900$\celsius$ and 950$\celsius$, respectively. The single crystals are characterized by transmission electron microscopy and X-ray diffraction. The misfit ... More
Superconductivity in alkali-earth metals doped phenanthreneOct 25 2011We discover superconductivity in alkali-earth metals doped phenanthrene. The superconducting critical temperatures \emph{T}$_c$ are 5.6 K and 5.4 K for Sr$_{1.5}$phenanthrene and Ba$_{1.5}$phenanthrene, respectively. The shielding fraction of Ba$_{1.5}$phenanthrene ... More
Inverse of magnetic dipole field using a reversible jump Markov chain Monte CarloOct 03 2013We consider a three-dimensional magnetic field produced by an arbitrary collection of dipoles. Assuming the magnetic vector or its gradient tensor field is measured above the earth surface, the inverse problem is to use the measurement data to find the ... More
Superconductivity and Phase Diagram in (Li$_{0.8}$Fe$_{0.2}$)OHFeSe$_{1-x}$S$_x$Jan 06 2015A series of (Li$_{0.8}$Fe$_{0.2}$)OHFeSe$_{1-x}$S$_x$ (0 $\leq$ x $\leq$ 1) samples were successfully synthesized via hydrothermal reaction method and the phase diagram is established. Magnetic susceptibility suggests that an antiferromagnetism arising ... More
Transport properties and magnetic field induced localization in the misfit cobaltite [Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystalSep 11 2007Resistivity under magnetic field, thermopower and Hall coefficient are systematically studied for [Bi$_2$Ba$_{1.3}$K$_{0.6}$Co$_{0.1}$]$^{RS}$[CoO$_2$]$_{1.97}$ single crystal. In-plane resistivity ($\rho_{ab}$(T)) shows metallic behavior down to 2 K ... More
Origin of superconductivity in nominally "undoped" T'-La$_{2-x}$Y$_{x}$CuO$_{4}$ filmsMar 25 2007We have systematically studied the transport properties of the La$_{2-x}$Y$_{x}$CuO$_{4}$(LYCO) films of T'-phase ($0.05\leq x \leq 0.30$). In this nominally "undoped" system, superconductivity was acquired in certain Y doping range ($0.10\leq x \leq ... More
Hysteresis and Anisotropic Magnetoresistance in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$Dec 22 2004The out-of-plane resistivity ($\rho_c$) and magnetoresistivity (MR) are studied in antiferromangetic (AF) $Nd_{2-x}Ce_xCuO_{4}$ single crystals, which have three types of noncollinear antiferromangetic spin structures. The apparent signatures are observed ... More
Anomalous Magnetoresistance in Pb-doped Bi$_2$Sr$_2$Co$_2$O$_y$ Single CrystalsDec 22 2004Magnetoresistance (MR) of the Bi$_{2-x}$Pb$_x$Sr$_2$Co$_2$O$_y$ ($x$=0, 0.3, 0.4) single crystals is investigated systematically. A nonmonotonic variation of the isothermal in-plane and out-of-plane MR with the field is observed. The out-of-plane MR is ... More
Effect of oxygen content on the transport properties and magnetoresistance in [Ca$_{2}$CoO$_{3-δ}$]$_{0.62}$[CoO$_{2}$] single crystalsDec 12 2004Transport property is investigated in [Ca$_{2}$CoO$_{3-\delta}$]$_{0.62}$[CoO$_{2}$] single crystals obtained by varying annealing conditions. The $\rho_{ab}(T)$ exhibits a resistivity minimum, and the temperature corresponding to this minimum increases ... More
Quantum Chaos at Finite Temperature - a New Approach via the Quantum ActionJun 28 2001We address the problem of quantum chaos: Is there a rigorous, physically meaningful definition of chaos in quantum physics? Can the tools of classical chaos theory, like Lyapunov exponents, Poincar\'e sections etc. be carried over to quantum systems? ... More
Renormalisation in Quantum MechanicsMar 05 2001Jun 26 2001We study a recently proposed quantum action depending on temperature. We construct a renormalisation group equation describing the flow of action parameters with temperature. At zero temperature the quantum action is obtained analytically and is found ... More
From Quantum Action to Quantum ChaosAug 21 2001We have recently suggested a quantum action, which has the form of a classical action and takes into account quantum effects via renormalized action parameters. Here we apply it to quantum chaos. We study a system in 2-D with weak anharmonic coupling ... More
Quantum Instantons and Quantum ChaosOct 27 1999Feb 05 2001Based on a closed form expression for the path integral of quantum transition amplitudes, we suggest rigorous definitions of both, quantum instantons and quantum chaos. As an example we compute the quantum instanton of the double well potential.
Interplay between periodicity and nonlinearity of indirect excitons in coupled quantum wellsMar 01 2012Inspired by a recent experiment of localization-delocalization transition (LDT) of indirect excitons in lateral electrostatic lattices [M. Remeika \textit{et al.}, Phys. Rev. Lett. \textbf{102}, 186803 (2009)], we investigate the interplay between periodic ... More
Integrated spectrum of the planetary nebula NGC 7027Jul 07 2005Aug 05 2005We present deep optical spectra of the archetypal young planetary nebula (PN) NGC 7027, covering a wavelength range from 3310 to 9160 A. The observations were carried out by uniformly scanning a long slit across the entire nebular surface, thus yielding ... More
Physical properties, strontium ordering and structural modulation in layered hexagonal Sr0.35CoO2Mar 07 2005Layered Sr0.35CoO2 has been synthesized by means of an ion exchange reaction from Na0.7CoO2. Resistivity measurements show that this material can be either metallic or semiconducting depending on the annealing conditions. Magnetic susceptibility, following ... More
New Upper Limit of Terrestrial Equivalence Principle Test for Rotating Extended BodiesMar 18 2003Mar 19 2003Improved terrestrial experiment to test the equivalence principle for rotating extended bodies is presented, and a new upper limit for the violation of the equivalence principle is obtained at the level of 1.6$% \times 10^{\text{-7}}$, which is limited ... More
Integer quantum Hall effect and topological phase transitions in siliceneDec 14 2017We numerically investigate the effects of disorder on the quantum Hall effect (QHE) and the quantum phase transitions in silicene based on a lattice model. It is shown that for a clean sample, silicene exhibits an unconventional QHE near the band center, ... More
Gap solitons of a super-Tonks-Girardeau gas in a one-dimensional periodic potentialFeb 01 2012We study the stability of gap solitons of the super-Tonks-Girardeau bosonic gas in one-dimensional periodic potential. The linear stability analysis indicates that increasing the amplitude of periodic potential or decreasing the nonlinear interactions, ... More
Six-dimensional weak-strong simulations of head-on beam-beam compensation in RHICOct 21 2014To compensate the large beam-beam tune spread and beam-beam resonance driving terms in the polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), we will introduce a low-energy DC electron beam into each ring to collide head-on with ... More
Transport Properties and Electronic Phase Diagram of Single-Crystalline Ca$_{10}$(Pt$_3$As$_8$) ((Fe$_{1-x}$Pt$_x$)$_2$As$_2$)$_5$Mar 07 2012Sizable single-crystalline samples of Ca$_{10}$(Pt$_3$As$_8$)((Fe$_{1-x}$Pt$_x$)$_2$As$_2$)$_5$ (the 10-3-8 phase) with 0$\leq x<$0.1 have been grown and systematically characterized via X-Ray diffraction, magnetic, and transport measurements. The undoped ... More
Phase Structure of Compact $QED_3$ with Massless FermionsDec 10 1992In the framework of (2+1)-dimensional compact lattice QED with light fermions, we investigate the phase diagram in the $(\beta, N)$ plane. The approximations involved are related to an expansion of the effective fermionic action as a power series of the ... More
Nodal gap in iron-based superconductor CsFe$_2$As$_2$ probed by quasiparticle heat transportFeb 10 2013Mar 26 2013The thermal conductivity of iron-based superconductor CsFe$_2$As$_2$ single crystal ($T_c =$ 1.81 K) was measured down to 50 mK. A significant residual linear term $\kappa_0/T$ = 1.27 mW K$^{-2}$ cm$^{-1}$ is observed in zero magnetic field, which is ... More
Doping dependent charge transfer gap and realistic electronic model of n-type cuprate superconductorsJul 16 2008Based on the analysis of the measurement data of angle-resolved photoemission spectroscopy (ARPES) and optics, we show that the charge transfer gap is significantly smaller than the optical one and is reduced by doping in electron doped cuprate superconductors. ... More
Reply to "Comment on 'Fano resonance for Anderson Impurity Systems' "Apr 07 2005Nov 21 2005In a recent Comment, Kolf et al. (cond-mat/0503669) state that our analysis of the Fano resonance for Anderson impurity systems [Luo et al., Phys. Rev. Lett 92, 256602 (2004)] is incorrect. Here we want to point out that their comments are not based on ... More
Closed Path Integrals and Renormalisation in Quantum MechanicsOct 18 1999Apr 13 2000We suggest a closed form expression for the path integral of quantum transition amplitudes. We introduce a quantum action with renormalized parameters. We present numerical results for the $V \sim x^{4}$ potential. The renormalized action is relevant ... More
Fermionic effective action and the pahse estructure of non compact quantum electrodynamics in 2+1 dimensionsMay 20 1993We study the phase diagram of non compact $QED_3$ using the microcanonical fermionic average method described elsewhere. We present evidence for a continuous phase transition line in the $\beta, N$ plane, extending down to arbitrarily small flavour number ... More
Thermodynamics from Monte Carlo HamiltonianFeb 11 2002We construct an effective low-energy Hamiltonian from the classical action via Monte Carlo with importance sampling. We use Monte Carlo (i) to compute matrix elements of the transition amplitude and (ii) to construct stochastically a basis. The MC Hamiltonian ... More
The Fano resonance for Anderson impurity systemsNov 24 2003Jul 28 2004We present a general theory for the Fano resonance in Anderson impurity systems. It is shown that the broadening of the impurity level leads to an additional and important contribution to the Fano resonance around the Fermi surface, especially in the ... More
Nonlinear dynamics in quantum physics- the study of quantum chaosMar 05 2002We use the quantum action to study the dynamics of quantum system at finite temperature. We construct the quantum action non-perturbatively and find temperature dependent action parameters. Here we apply the quantum action to study quantum chaos. We present ... More
Quantum Chaos at Finite TemperatureJun 23 2001We use the quantum action to study quantum chaos at finite temperature. We present a numerical study of a classically chaotic 2-D Hamiltonian system - harmonic oscillators with anharmonic coupling. We construct the quantum action non-perturbatively and ... More
New Method for Dynamical Fermions and Chiral-Symmetry BreakingNov 26 1993The reasons for the feasibility of the Microcanonical Fermionic Average ($MFA$) approach to lattice gauge theory with dynamical fermions are discussed. We then present a new exact algorithm, which is free from systematic errors and convergent even in ... More
Superconductivity in LiFeO2Fe2Se2 with anti-PbO-type Spacer LayersSep 16 2013Sep 29 2013Superconductivity has been found in the iron-arsenides with different structures by alternative stacking of the conducting Fe2As2 layers and spacer layers including alkali- or alkali-earth metal ions and PbO- or perovskite-type oxides blocks. So far, ... More
Magnetic and transport properties in Gd$_{1-x}$Sr$_x$CoO$_{3}$ ($x$= 0.10-0.70)Jan 24 2005Mar 28 2006Magnetic and transport properties of polycrystalline Gd$_{1-x}$Sr$_x$CoO$_{3}$ ($x$= 0.10-0.70) are investigated systemically. Cluster-glass magnetism for $x \leq$ 0.45 and long-range ferromagnetic order in higher doping level are observed. Transport ... More
Phase diagram and physical properties of NaFe$_{1-x}$Cu$_x$As single crystalsJul 23 2013A series of high quality NaFe$_{1-x}$Cu$_x$As single crystals has been grown by a self-flux technique, which were systematically characterized via structural, transport, thermodynamic, and high pressure measurements. Both the structural and magnetic transitions ... More
Ensemble Kalman filter with the unscented transformJan 05 2009A modification scheme to the ensemble Kalman filter (EnKF) is introduced based on the concept of the unscented transform (Julier et al., 2000; Julier and Uhlmann, 2004), which therefore will be called the ensemble unscented Kalman filter (EnUKF) in this ... More
Heat transport in RbFe2As2 single crystal: evidence for nodal superconducting gapMar 02 2014Jan 06 2015The in-plane thermal conductivity of iron-based superconductor RbFe$_2$As$_2$ single crystal ($T_c \approx$ 2.1 K) was measured down to 100 mK. In zero field, the observation of a significant residual linear term $\kappa_0/T$ = 0.65 mW K$^{-2}$ cm$^{-1}$ ... More
QCD with dynamical Wilson fermions - first results from SESAMOct 02 1995First results of a recently started simulation of full QCD with two flavours of sea-quarks at a coupling of $\beta = 5.6$ on a $16^3 \times 32$ lattice are presented. Emphasis is laid on the statistical significance that can be achieved by an ``integrated ... More
Giant Anisotropy of Magnetoresistance and "Spin Valve" effect in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$Jul 01 2007Mar 20 2009We have studied anisotropic magnetoresistance (MR) and magnetization with rotating magnetic field (B) within $CuO_2$ plane in lightly doped AF $Nd_{2-x}Ce_xCuO_{4}$. \emph{A giant anisotropy} in MR is observed at low temperature below 5 K. The c-axis ... More
Magnetic field induced spin-flop transition in Na$_x$CoO$_2$ (0.5$<$x$<$0.55)Mar 25 2007The isothermal magnetoresistance (MR) with magnetic field (H) parallel to and perpendicular to ab plane is systematically studied on the single crystal Na$_{0.52}$CoO$_2$ with charge ordering at $\sim 50$ K and an in-plane ferromagnetism below 25 K. The ... More
Superconductivity at 5 K in potassium doped phenanthreneFeb 20 2011Organic materials are believed to be potential superconductor with high transition temperature (TC). Organic superconductors mainly have two families: the quasi-one dimensional (TMTSF)2X and two dimensional (BEDT-TTF)2X (Ref. 1 and 2), in which TMTSF ... More
Gate-tuned Superconductor-Insulator transition in (Li,Fe)OHFeSeMar 09 2015The antiferromagnetic(AFM) insulator-superconductor transition has been always a center of interest in the underlying physics of unconventional superconductors. The quantum phase transition between Mott insulator with AFM and superconductor can be induced ... More
Power-law Temperature Dependent Hall Angle in the Normal State and its Correlation with Superconductivity in iron-pnictidesJan 09 2013We report Hall measurement of the normal state in K- and Co-doped BaFe$_2$As$_2$, as well NaFe$_{1-x}$Co$_x$As. We found that a power-law temperature dependence of Hall angle, cot$\theta_{\rm H}$$\propto$ $T^\beta$, prevails in normal state with temperature ... More
Large magnetic anisotropy in $Fe_xTaS_2$ single crystalsMay 09 2017In intercalated transition metal dichalcogenide $Fe_xTaS_2$ (0.2 $\leq$ x $\leq$ 0.4) single crystals, large magnetic anisotropy is observed. Transport property measurements indicate that heavy Fe-doping leads to a large anisotropy of resistivity ($\rho$$_{c}$/$\rho$$_{ab}$). ... More
Single crystal growth and characterizations of Cu0.03TaS2 superconductorsAug 18 2008Dec 23 2008Single crystal of Cu0.03TaS2 with low copper intercalated content was successfully grown via chemical iodine-vapor transport. The structural characterization results show that the copper intercalated 2H-Cu0.03TaS2 single crystal has the same structure ... More
Doping evolution of the superconducting gap structure in heavily hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$: heat transport studyJan 04 2014Aug 03 2015We performed systematic thermal conductivity measurements on heavily hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals with 0.747 $\leq x \leq$ 0.974. At $x$ = 0.747, the $\kappa_0/T$ is negligible, indicating nodeless superconducting gap. A small ... More
Breakdown of single spin-fluid model in heavily hole-doped superconductor CsFe2As2May 28 2017Although Fe-based superconductors are multiorbital correlated electronic systems, previous nuclei magnetic resonance (NMR) measurement suggests that a single spin-fluid model is sufficient to describe its spin behavior. Here, we firstly observed the breakdown ... More
Evidence for nodeless superconducting gap in NaFe$_{1-x}$Co$_x$As from low-temperature thermal conductivity measurementsApr 16 2012Apr 19 2012The thermal conductivity of optimally doped NaFe$_{0.972}$Co$_{0.028}$As ($T_c \sim$ 20 K) and overdoped NaFe$_{0.925}$Co$_{0.075}$As ($T_c \sim$ 11 K) single crystals were measured down to 50 mK. No residual linear term $\kappa_0/T$ is found in zero ... More
Evolution of band structure from optimally doped to heavily overdoped Co-substituted NaFeAsJun 20 2012Using angle-resolved photoemission spectroscopy, we studied the electronic structure of NaFe$_{1-x}$Co$_x$As from an optimally doped superconducting compound ($x=0.028$) to a heavily overdoped non-superconducting one ($x=0.109$). Similar to the case of ... More
Magnetic properties in the doped spin-1/2 honeycomb-lattice compound In$_3$Cu$_2$VO$_9$Jun 09 2011We report the magnetic properties in the Co- and Zn-doped spin-1/2 honeycomb-lattice compound In$_3$Cu$_2$VO$_9$. The magnetic susceptibility and specific heat experiments show no long-range ordering down to 2 K in In$_3$Cu$_2$VO$_9$. In the low temperature ... More
Structure determination and coexistence of superconductivity and antiferromagnetic order in (Li0.8Fe0.2)OHFeSeAug 09 2014FeSe-derived superconductors show some unique behaviors relative to iron-pnictide superconductors, which are very helpful to understand the mechanism of superconductivity in high-Tc iron-based superconductors. The low-energy electronic structure of the ... More
Doping Effects on the two-dimensional Spin Dimer Compound $SrCu_2(BO_3)_2$Jun 14 2004A series of compounds M$_{0.1}$Sr$_{0.9}$Cu$_2$(BO$_3$)$_2$ with Sr substituted by M=Al, La, Na and Y were prepared by solid state reaction. XRD analysis showed that these doping compounds are isostructural to SrCu$_2$(BO$_3$)$_2$. The magnetic susceptibility ... More
Windows open for highly tunable magnetostructural phase transitionsJul 18 2016An attempt was made to tailor the magnetostructural transitions (MSTs) over a wide temperature range under the principle of isostructural alloying. A series of wide Curie-temperature windows (CTWs) with a maximal width of 377 K between 69 and 446 K were ... More
Evolution of high-temperature superconductivity from low-Tc phase tuned by carrier concentration in FeSe thin flakesSep 02 2015In contrast to bulk FeSe superconductor, heavily electron-doped FeSe-derived superconductors show relatively high Tc without hole Fermi surfaces and nodal superconducting gap structure, which pose great challenges on pairing theories in the iron-based ... More
Pressure effects on superconducting properties of single-crystalline Co doped NaFeAsJul 23 2012Resistivity and magnetic susceptibility measurements under external pressure were performed on single-crystals NaFe1-xCoxAs (x=0, 0.01, 0.028, 0.075, 0.109). The maximum Tc enhanced by pressure in both underdoped and optimally doped NaFe1-xCoxAs is the ... More
Transport and anisotropy in single-crystalline SrFe$_2$As$_2$ and $A_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($A$ = Sr, Ba) superconductorsJun 16 2008Nov 21 2008We have successfully grown high quality single crystals of SrFe$_2$As$_2$ and A$_{0.6}$K$_{0.4}$Fe$_2$As$_2$(A=Sr, Ba) using flux method. The resistivity, specific heat and Hall coefficient have been measured. For parent compound SrFe$_2$As$_2$, an anisotropic ... More
Electronic structure in one-Fe Brillouin zone of iron-pnictide superconductor CsFe$_2$As$_2$Sep 08 2014Sep 09 2014The multiband nature of iron-pnictide superconductors is one of the keys to the understanding of their intriguing behavior. The electronic and magnetic properties heavily rely on the multiband interactions between different electron and hole pockets near ... More
Ultralow-frequency collective compression mode and strong interlayer coupling in multilayer black phosphorusMar 23 2015Jun 13 2015The recent renaissance of black phosphorus (BP) as a two-dimensional 2D layered material has generated tremendous interest in its tunable electronic band gap and highly anisotropic transport properties that offer new opportunities for device applications. ... More
Rearrangement of Sodium ordering and its effect on physical properties in $Na_xCoO_2$ systemAug 31 2008We systematically study Raman spectroscopy of cleaved Na$_x$CoO$_2$ single crystals with 0.37 $\leq$ x $\leq$ 0.80. The Raman shift of A$_{1g}$ mode is found to be linearly dependent on Na content, while the Raman shift of E$_{1g}$ mode has an abnormal ... More
Magnetic phase diagram in the Co-rich side of LnCo1-xFexAsO (Ln=La, Sm) systemAug 23 2012Jan 11 2013The magnetic phase diagram has been mapped out via the measurements of electronic resistivity, magnetization and specific heat in the cobalt-based layered LnCo1-xFexAsO (Ln=La, Sm) compounds. The ferromagnetic (FM) transition at 63 K for LaCoAsO is rapidly ... More
Neutron and X-ray diffraction study of cubic [111] field cooled Pb(Mg1/3Nb2/3)O3Dec 02 2007Neutron and x-ray diffraction techniques have been used to study the competing long and short-range polar order in the relaxor ferroelectric Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$ (PMN) under a [111] applied electric field. Despite reports of a structural transition ... More
Metamagnetic Transition in Na$_{0.85}$CoO$_2$ Single CrystalsApr 19 2004Nov 02 2004We report the magnetization, specific heat and transport measurements of high quality Na$_{0.85}$CoO$_2$ single crystals in applied magnetic fields up to 14T. In high temperatures, the system is in a paramagnetic phase. It undergoes a magnetic phase transition ... More
Possible high temperature superconductivity in Ti-doped A-Sc-Fe-As-O (A= Ca, Sr) systemMar 30 2009Sep 17 2009We report a systematic study on the effect of partial substitution of Sc$^{3+}$ by Ti$^{4+}$ in Sr$_{2}$ScFeAsO$_{3}$, Ca$_{2}$ScFeAsO$_{3}$ and Sr$_{3}$Sc$_{2}$Fe$_{2}$As$_{2}$O$_{5}$ on their electrical properties. High level of doping results in an ... More
Some Interesting Features of Noncompact QED_3Nov 27 1993We study the phase diagram of non compact $QED_3$ using the $MFA$ method and present evidence for a continuous phase transition line at small $N_f$. We also analyze the chiral structure of the vacuum by means of the computation of the probability distribution ... More
Infrared spectrum and its implications for the electronic structure of the semiconducting iron selenide K$_{0.83}$Fe$_{1.53}$Se$_2$Jan 03 2011Jun 16 2011We report an infrared spectroscopy study on K$_{0.83}$Fe$_{1.53}$Se$_2$, a semiconducting parent compound of the new iron-selenide system. The major spectral features are found to be distinctly different from all other Fe-based superconducting systems. ... More
An equation of state from cool-dense fluids to hot gases for mixed elementsNov 22 1997An equation of state for the domain extending from hot gases to cool-dense fluids is formulated for a hydrogen-helium mixture. The physical processes take account of temperature ionization and dissociation, electron degeneracy, Coulomb coupling and pressure ... More
SDW transition of Fe1 zigzag chains and metamagnetic transition of Fe2 in TaFe$_{1+y}$Te$_3$Jul 13 2011We systematically study the AFM order of Fe1 zigzag chains and spin-flop of excess Fe2 under high magnetic field H through the susceptibility, magnetoresistance (MR), Hall effect and specific heat measurements in high-quality single crystal TaFe$_{1+y}$Te$_3$. ... More
Superconductivity and Magnetic Properties of high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs)Dec 27 2010We successfully grew the high-quality single crystals of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs) by self-flux method. Sharp superconducting transition was observed for both types of crystals. The crystals show the onset superconducting transition temperatures ... More
Universal V-shaped temperature-pressure phase diagram in the iron-based superconductors KFe2As2, RbFe2As2, and CsFe2As2Dec 19 2014Feb 17 2015We report a sudden reversal in the pressure dependence of Tc in the iron-based superconductor RbFe2As2, at a critical pressure Pc = 11 kbar. Combined with our prior results on KFe2As2 and CsFe2As2, we find a universal V-shaped phase diagram for Tc vs ... More
Electronic and magnetic phase diagram in K$_x$Fe$_{2-y}$Se$_2$ superconductorsApr 26 2011The correlation and competition between antiferromagnetism and superconductivity are one of the most fundamental issues in all of high temperature superconductors. The superconductivity in high temperature cuprate superconductors arises from suppressing ... More
Physical properties of $A_x$Fe$_{2-y}$S$_2$ ($A$=K, Rb and Cs) single crystalsJan 09 2012We successfully synthesized two new compounds Rb$_x$Fe$_{2-y}$S$_2$ and Cs$_x$Fe$_{2-y}$S$_2$ which were isostructural with K$_x$Fe$_{2-y}$Se$_2$ superconductor. We systematically investigated the resistivity, magnetism and thermoelectric power of $A_x$Fe$_{2-y}$S$_2$ ... More
Reversible room-temperature magnetocaloric effect with large temperature span in antiperovskite compounds Ga1-xCMn3+x (x=0, 0.06, 0.07, and 0.08)May 12 2009May 18 2009The magnetic and magnetocaloric properties of Ga1-xCMn3+x have been investigated. Reversible magnetocaloric effect (MCE) occurs near the Curie temperature TC. The magnetic entropy change decreases with increasing x, though TC and magnetization increases. ... More
Emergent Kondo scaling in iron-based superconductors AFe2As2 (A = K, Rb, Cs)Jul 31 2015Nov 22 2015Unconventional superconductivity from heavy fermion (HF) is always observed in f-electron systems, in which Kondo physics between localized f-electrons and itinerant electrons plays an essential role. Whether HF superconductivity could be achieved in ... More
Magnetoresistance evidence on surface state and field-dependent bulk gap in Kondo insulator SmB6Sep 10 2013Mar 27 2015Recently, the resistance saturation at low temperature in Kondo insulator SmB6, a long-standing puzzle in condensed matter physics, was proposed to originate from topological surface state. Here,we systematically studied the magnetoresistance of SmB6 ... More
Coexistence of superconductivity and antiferromagnetism in single crystals $A_{0.8}Fe_{2-y}Se_2$ (A= K, Rb, Cs, Tl/K and Tl/Rb): evidence from magnetization and resistivityFeb 14 2011We measure the resistivity and magnetic susceptibility in the temperature range from 5 K to 600 K for the single crystals $A$Fe$_{2-y}$Se$_2$ ($A$ = K$_{0.8}$, Rb$_{0.8}$, Cs$_{0.8}$, Tl$_{0.5}$K$_{0.3}$ and Tl$_{0.4}$Rb$_{0.4}$). A sharp superconducting ... More
Phase diagram as a function of doping level and pressure in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ systemJan 09 2012We establish the phase diagram of Eu$_{1-x}$La$_x$Fe$_2$As$_2$ system as a function of doping level x and the pressure by measuring the resistivity and magnetic susceptibility. The pressure can suppress the spin density wave (SDW) and structural transition ... More
Origin of the structural phase transition at 130 K in BaNi$_2$As$_2$: a combined study of optical spectroscopy and band structure calculationsMay 06 2009May 08 2009BaNi$_2$As$_2$ exhibits a first order structural transition at 130 K. Understanding this structural transition is a crucial step towards understanding the electronic properties of the material. We present a combined optical spectroscopy and band structure ... More
Electronic properties of single-crystalline Fe$_{1.05}$Te and Fe$_{1.03}$Se$_{0.30}$Te$_{0.70}$Nov 10 2008We report on a comprehensive study of the transport, specific heat, magnetic susceptibility and optical spectroscopy on single crystal of Fe$_{1.05}$Te. We confirm that Fe$_{1.05}$Te undergoes a first-order phase transition near 65 K. However, its physical ... More
Study of Relay Selection for Physical-Layer Security in Buffer-Aided Relay Networks Based on the Secrecy Rate CriterionMay 15 2016In this paper, we investigate an opportunistic relay and jammer scheme along with relay selection algorithms based on the secrecy rate criterion in multiple-input multiple-output buffer-aided down link relay networks, which consist of one source, a number ... More
Anisotropic, Intermediate Coupling Superconductivity in Cu0.03TaS2Nov 21 2008Mar 12 2009The anisotropic superconducting state properties in Cu0.03TaS2 have been investigated by magnetization, magnetoresistance, and specific heat measurements. It clearly shows that Cu0.03TaS2 undergoes a superconducting transition at TC = 4.03 K. The obtained ... More
Transport and magnetic properties of La-doped CaFe$_2$As$_2$Feb 16 2012We measured the transport properties and susceptibility of single crystals Ca$_{1-x}$La$_x$Fe$_2$As$_2$(x=0, 0.05, 0.1, 0.15, 0.19 and 0.25). Large in-plane resistivity anisotropy similar to that in Co-doped 122 iron-pnictides is observed although no ... More
Reentrant spin-glass behavior in $TlFe_{2-x}Se_2$ with the $ThCr_2Si_2$-type structureDec 14 2010We investigated the physical properties of $TlFe_{2-x}Se_2$ single crystals. The resistivity of $TlFe_{2-x}Se_2$ shows typical semiconductor behavior with an activation energy of 25 meV. DC susceptibility indicates an antiferromagnetic transition at about ... More
Enhanced Superconductivity by Rare-earth Metal-doping in PhenanthreneMar 27 2012We successfully synthesized La- and Sm-doped phenanthrene powder samples and discovered superconductivity at $T_{\rm c}$ around 6 K in them. The $T_{\rm c}$s are 6.1 K for LaPhenanthrene and 6.0 K for SmPhenanthrene, which are enhanced by about 1 K and ... More
Superconductivity at 32 K in single crystal Rb$_{0.78}$Fe$_2$Se$_{1.78}$}Dec 26 2010We successfully grew the high-quality single crystal of Rb$_{0.78}$Fe$_2$Se$_{1.78}$, which shows sharp superconducting transition in magnetic susceptibility and electrical resistivity. Resistivity measurements show the onset superconducting transition ... More
Crystal structure, physical properties and superconductivity in $A_{x}$Fe$_2$Se$_2$ single crystalsJan 29 2011We studied the correlation among structure and transport properties and superconductivity in the different $A_x$Fe$_2$Se$_2$ single crystals ($A$ = K, Rb, and Cs). Two sets of (00$l$) reflections are observed in the X-ray single crystal diffraction patterns, ... More
Pressure effect on superconductivity of $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs)Jan 06 2011We performed the high hydrostatic pressure resistivity measurements (up to 1.7 GPa) on the newly discovered superconductors $A_{x}$Fe$_2$Se$_2$ ($A$ = K and Cs) single crystals. Two batches of single crystals $K_xFe_2Se_2$ with different transition temperatures ... More