In this paper, we consider a system consisting of two capacitively coupled superconducting islands viaJosephson junctions. We show that it can be reduced to two coupling harmonic oscillators under certain conditions,a...In this paper, we consider a system consisting of two capacitively coupled superconducting islands viaJosephson junctions. We show that it can be reduced to two coupling harmonic oscillators under certain conditions,and can be solved exactly in terms of a displacing transformation, a beam-splitter-like transformation, and a squeezingtransformation. It is found that the system evolves by a rotated-squeezed-coherent state when the system is initially in acoherent state. Quantum dynamics of the Cooper pairs in the two superconducting islands are investigated. It is shownthat the number of the Cooper pairs in the two islands evolves periodically.展开更多
The effect of an applied magnetic field on an inhomogeneous superconductor is studied and the value of the lower critical magnetic field HC1 at which superconducting vortices appear is estimated. In addition, the auth...The effect of an applied magnetic field on an inhomogeneous superconductor is studied and the value of the lower critical magnetic field HC1 at which superconducting vortices appear is estimated. In addition, the authors locate the vortices of local minimizers, which depends on the inhomogeneous term a(x).展开更多
Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extrem...Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic.Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer Fe Se on Mg O(001) substrate by transport measurement.Scanning transmission electron microscopy investigation on the interface structure indicates that Fe Se films grow epitaxially on Mg O(001) and that overlayer Fe atoms diffuse into the top two layers of Mg O and substitute Mg atoms.Our density functional theory calculations reveal that this substitution promotes the charge transfer from the Mg O substrate to the Fe Se films,an essential process that also occurs in monolayer Fe Se on TiO_2-terminated oxides and contributes to the enhanced superconductivity therein.Our finding suggests that superconductivity enhancement in monolayer Fe Se films on oxides substrates is rather general as long as charge transfer is allowed at the interface,thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.展开更多
The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-conne...The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-connected Jaynes-Cummings lattice, which can be constructed with superconducting circuits. This model is composed of alternatively connected qubits and cavity modes.Using a numerical method, we show that by varying the detuning between the qubits and the cavities, a phase transition from the superfluid phase to the Mott insulator phase occurs at commensurate fillings in a one-dimensional array. We study the phase transition in lattices with symmetric and asymmetric couplings, respectively.展开更多
文摘In this paper, we consider a system consisting of two capacitively coupled superconducting islands viaJosephson junctions. We show that it can be reduced to two coupling harmonic oscillators under certain conditions,and can be solved exactly in terms of a displacing transformation, a beam-splitter-like transformation, and a squeezingtransformation. It is found that the system evolves by a rotated-squeezed-coherent state when the system is initially in acoherent state. Quantum dynamics of the Cooper pairs in the two superconducting islands are investigated. It is shownthat the number of the Cooper pairs in the two islands evolves periodically.
基金Project supported by the National Natural Science Foundation of China (No.10071067) the Excellent Young Teachers Program of the Ministry of Education of China, the Jiangsu Provincial National Science Foundation of China and the Combinatorial and Comput
文摘The effect of an applied magnetic field on an inhomogeneous superconductor is studied and the value of the lower critical magnetic field HC1 at which superconducting vortices appear is estimated. In addition, the authors locate the vortices of local minimizers, which depends on the inhomogeneous term a(x).
基金supported by the National Natural Science Foundation of China(11574174,11774193,11790311,11404183,11474030,21573121 and 51421002)the National Basic Research Program of China(2015CB921000)+1 种基金the President Foundation of China Academy of Engineering Physics(YZJJLX2016010)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB07030200)
文摘Interface enhanced superconductivity over 50 K has been discovered in monolayer Fe Se films grown on several TiO_2-terminated oxide substrates.Whether such phenomenon exists in other oxide substrates remains an extremely interesting topic.Here we report enhanced superconductivity with an onset transition temperature of 18 K in monolayer Fe Se on Mg O(001) substrate by transport measurement.Scanning transmission electron microscopy investigation on the interface structure indicates that Fe Se films grow epitaxially on Mg O(001) and that overlayer Fe atoms diffuse into the top two layers of Mg O and substitute Mg atoms.Our density functional theory calculations reveal that this substitution promotes the charge transfer from the Mg O substrate to the Fe Se films,an essential process that also occurs in monolayer Fe Se on TiO_2-terminated oxides and contributes to the enhanced superconductivity therein.Our finding suggests that superconductivity enhancement in monolayer Fe Se films on oxides substrates is rather general as long as charge transfer is allowed at the interface,thus pointing out an explicit direction for searching for new high temperature superconductivity by interface engineering.
基金supported by the National Science Foundation under Award Number(Grant No.0956064)
文摘The connectivity and tunability of superconducting quantum devices provide a rich platform to build quantum simulators and study novel many-body physics. Here we study quantum phase transition in a detuned multi-connected Jaynes-Cummings lattice, which can be constructed with superconducting circuits. This model is composed of alternatively connected qubits and cavity modes.Using a numerical method, we show that by varying the detuning between the qubits and the cavities, a phase transition from the superfluid phase to the Mott insulator phase occurs at commensurate fillings in a one-dimensional array. We study the phase transition in lattices with symmetric and asymmetric couplings, respectively.
