A5067732227- Physics of Superconductivity and Magnetism
- Superconductivity in MgB2 and Alloys
- Iron-based superconductors research
- Superconducting Materials and Applications
- Magnetic properties of thin films
- Particle accelerators and beam dynamics
- Silicon Carbide Semiconductor Technologies
- Quantum and electron transport phenomena
- Magnetic confinement fusion research
- Acoustic Wave Resonator Technologies
- Layered Double Hydroxides Synthesis and Applications
- Electromagnetic Simulation and Numerical Methods
- Photonic and Optical Devices
- Spectroscopy and Laser Applications
- Metal and Thin Film Mechanics
- Surface and Thin Film Phenomena
- ZnO doping and properties
- Advanced Fiber Laser Technologies
Tianjin University
2023
Nanjing University
1995-2014
Forschungszentrum Jülich
2000-2006
National University of Singapore
1999-2000
Nanjing University of Posts and Telecommunications
1998
This paper studies the suppression of superconducting transition temperature (Tc) ultrathin NbN film. We fabricated epitaxial thin films thicknesses ranging from 2.5 to 100 nm on single crystal MgO (100) substrates by dc magnetron sputtering. performed structure analyses and measured their electric far infrared properties. The experimental results were compared with several mechanisms superconductivity proposed in literature, including weak localization effect, proximity quantum size effect...
We have measured the temperature dependence of microwave surface impedance ${Z}_{s}{=R}_{s}+i\ensuremath{\omega}{\ensuremath{\mu}}_{0}\ensuremath{\lambda}$ two c-axis oriented ${\mathrm{MgB}}_{2}$ films employing dielectric resonator techniques. The magnetic-field penetration depth \ensuremath{\lambda} determined by a sapphire at 17.9 GHz can be well fitted from 5 K close to ${T}_{c}$ standard BCS integral expression assuming reduced energy gap $\ensuremath{\Delta}{(0)/kT}_{c}$ as low 1.13...
Lattice mismatch between NbN and silicon (Si) reduces the superconducting properties of film on Si substrate, this in turn affects performance devices such as hot electron bolometer (HEB) nanowire single photon detector (SNSPD). We have found that will be significantly improved by a Nb5N6 buffer layer. The strain was optimized varying thickness With 30 nm thick Nb5N6, zero resistance transition temperature (TC0) 6 is up to 13.5 K critical current density (JC) more than 107 A cm−2. All...
The dependences of magnetic field penetration depth at zero temperature λ(0), microwave surface resistance Rs and π-band energy gap Δπ(0) on the normal-state resistivity right above critical temperature, ρ0, were studied for MgB2 thin films prepared by different techniques employing a sapphire resonator technique. We found that zero-temperature λ(0) data could be well fitted yielding London λL 34.5 nm, where ξ0 is coherence length, mean free path determined from ρ0. 15 20 K increases roughly...
We report on terahertz (THz) surface impedance measurement of an epitaxial MgB2 thin film using time domain THz spectroscopy. show that the resistance is much lower than YBa2Cu3O7−δ and copper in range. A linear dependence reactance frequency observed, yielding a penetration depth about 100nm at low temperatures. The measurements agree qualitatively with calculations based impurity scattering Born limit. Our results clearly indicate films have great potential for electronic applications.
By incorporating an anomalous weak link (AWL), the coupled-grain model is modified to describe decrease of microwave surface impedance (Zs) YBa2Cu3O7-δ thin films in a dc magnetic field (Bdc). The critical current density AWL has minimum at zero Bdc, linear dependence on Bdc for low and saturation high unlike conventional link. Using this model, dependences resistance are calculated different rf input powers resonant modes. dimensionless parameters rH, defined as ratio change reactance, also...
The microwave surface impedance Z/sub s/=R/sub s/+j/spl omega//spl mu//sub 0//spl lambda/ of MgB/sub 2/ thin films was measured via advanced dielectric resonator (DR) techniques. First, the temperature dependence penetration depth /spl with a sapphire puck at 17.9 GHz can be well fitted from 5 K close to T/sub c/ by standard BCS integral expression assuming reduced energy gap Delta/(0)/kT/sub as low 1.0-1.1 lambda/(0)=100--110 nm. These results clearly indicate s-wave nature order parameter....
There is an increasing demand for high-precision gas absorption spectroscopy in basic research and industrial applications, such as tracking leak warning. In this Letter, a novel, to the best of our knowledge, real-time detection method proposed. A femtosecond optical frequency comb used light source, broadening pulse containing range oscillation frequencies formed after passing through dispersive element Mach-Zehnder interferometer. Four lines H13C14N cells are measured at five different...
The microwave surface impedance Zs = Rs + jωμ0λ was measured with dielectric resonator techniques for two c-axis-oriented MgB2 thin films. temperature dependence of the penetration depth λ a sapphire at 17.93 GHz can be well fitted from 5 K close to Tc by standard BCS integral expression assuming reduced energy gap Δ(0)/kTc as low 1.13 and 1.03 samples. From these fits zero temperatures determined 102 nm 107 nm, respectively. results clearly indicate s-wave nature order parameter. resistance...
Assuming that a high-Tc superconducting thin film is composed of network grains connected by grain-boundary weak links, the equation describing its response under microwave current irf solved using perturbation method to third order irf. Based on obtained results, analytic expressions for film’s surface impedance are derived, revealing dependence rf magnetic field in low and intermediate limit. Good qualitative agreement with experiments observed.
An unusual microwave response of the surface impedance Zs high-Tc thin films at an applied small dc magnetic field (Bdc) 77 K, namely a decrease Zs, is observed with microstrip resonator technique. The resonant frequency 1.107 GHz. direction Bdc parallel or perpendicular to a-b plane. ranges from 0 200 G. It found that resistance (Rs) plane first decreases and then increases above crossover field. Rs behaviour for same but different two behaviours can be collapsed one curve by scaling...
For microstrip resonators fabricated from YBa2Cu3O7- delta (YBCO) thin film on LaAlO3 (001) substrates, this paper reports the experimental observation and theoretical explanation of power dependence unloaded quality factor (Q0). Two kinds Q0 behaviour were observed. In one case, with increase input power, dropped at first rather quickly, then slowly again drastically. other remained almost unchanged but, beyond a certain level, very rapidly. To interpret these behaviours, two...
Two issues related to the microwave surface impedance Z_s of MgB_2 thin film are discussed in this Letter, both being significant for potential applications. At first, a correlation between Zs and Alpha = Xi/l was found, where Xi is coherence length, l mean free path. The resistance Rs decreases with at moderate large values saturates when approaches one. penetration depth zero temperature Lamda(0) different films could be well fitted by Lamda_L (1+Alpha)^(1/2), yielding London 33.6 nm....
We have measured the temperature dependence of microwave surface impedance Z_s = R_s + i\Omega\mu_0 a MgB2 film at frequency \Omega /2\Pi 18 GHz employing dielectric resonator technique. found that magnetic field penetration depth \Lamda can be fitted by \Lamda(T)= \Lamda(0) [1-(T/Tc)^2] ^(-1/2) with \Lamda(0)=(260 +/- 20)nm. The absolute value was confirmed direct measurements submillimeter wave transmission spectroscopy 430 GHz. analysis \Lamda(T) data below Tc/2 revealed significant...