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Cited by 10
- 15 March 2016
- Published by Physical Society of Japan in Journal of the Physical Society of Japan
Nature of Driving Force on an Isolated Moving Vortex in Dirty Superconductors
by Yusuke Kato, Chun-Kit Chung
We reconsider the force-balance relation on an isolated vortex in the flux flow state within the scheme of the time-dependent Ginzburg–Landau (TDGL) equation. We define the force on a vortex by the total force on superconducting electrons in the region S surrounding the vortex. We derive the local momentum balance relation of superconducting electrons and then find the force-balance relation on an isolated vortex while taking account of the fact that the transport current in charged superconductors is inherently spatially varying with the scale of the penetration depth λ. We also find that the nature of the driving force is hydrodynamic when S is a disk with radius R satisfying ξ ≪ R ≪ λ (ξ is the coherence length) while the hydrodynamic and magnetic parts contribute equally to the driving force for $\lambda \lesssim R$.
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- 15 March 2016
- Published by Physical Society of Japan in Journal of the Physical Society of Japan
Nature of Driving Force on an Isolated Moving Vortex in Dirty Superconductors
by Yusuke Kato, Chun-Kit Chung
We reconsider the force-balance relation on an isolated vortex in the flux flow state within the scheme of the time-dependent Ginzburg–Landau (TDGL) equation. We define the force on a vortex by the total force on superconducting electrons in the region S surrounding the vortex. We derive the local momentum balance relation of superconducting electrons and then find the force-balance relation on an isolated vortex while taking account of the fact that the transport current in charged superconductors is inherently spatially varying with the scale of the penetration depth λ. We also find that the nature of the driving force is hydrodynamic when S is a disk with radius R satisfying ξ ≪ R ≪ λ (ξ is the coherence length) while the hydrodynamic and magnetic parts contribute equally to the driving force for $\lambda \lesssim R$.
Cited by 10
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- 8 February 2016
- Published by arXiv in arXiv
Nature of driving force on an isolated moving vortex in dirty superconductors
by Yusuke Kato, Chun-Kit Chung
We reconsider the force-balance relation on an isolated vortex in the flux flow state within the scheme of time-dependent-Ginzburg-Landau (TDGL) equation. We define force on the vortex by the total force on superconducting electrons in the region $S$ surrounding the vortex. We derive the local momentum balance relation of superconducting electrons and then find the force-balance relation on isolated vortex with taking account of the fact that the transport current in charged superconductors are inherently spatially varying with the scale of penetration depth $\lambda$. We also find that nature of the driving force is hydrodynamic when $S$ is the disk with radius $R$ satisfying $\xi\ll R\ll \lambda$ ($\xi$ is the coherence length) while the hydrodynamic and magnetic parts contribute equally to the driving force for $\lambda \lesssim R$.
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- 8 February 2016
- Published by arXiv in arXiv
Open Access
Nature of driving force on an isolated moving vortex in dirty superconductors
by Yusuke Kato, Chun-Kit Chung
We reconsider the force-balance relation on an isolated vortex in the flux flow state within the scheme of time-dependent-Ginzburg-Landau (TDGL) equation. We define force on the vortex by the total force on superconducting electrons in the region $S$ surrounding the vortex. We derive the local momentum balance relation of superconducting electrons and then find the force-balance relation on isolated vortex with taking account of the fact that the transport current in charged superconductors are inherently spatially varying with the scale of penetration depth $\lambda$. We also find that nature of the driving force is hydrodynamic when $S$ is the disk with radius $R$ satisfying $\xi\ll R\ll \lambda$ ($\xi$ is the coherence length) while the hydrodynamic and magnetic parts contribute equally to the driving force for $\lambda \lesssim R$.
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- 8 October 2013
- Published by Springer Nature in Journal of Low Temperature Physics
Zero-Field Vortex-Induced Hall Effect and Polar Kerr Effect in Chiral p-Wave Superconductors near Kosterlitz-Thouless Transition
by C. K. Chung, Y. Kato
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- 8 October 2013
- Published by Springer Nature in Journal of Low Temperature Physics
Zero-Field Vortex-Induced Hall Effect and Polar Kerr Effect in Chiral p-Wave Superconductors near Kosterlitz-Thouless Transition
by C. K. Chung, Y. Kato
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- 29 September 2010
- Published by American Physical Society (APS) in Physical Review A
Pairing and coherence order parameters in a three-component ultracold Fermi gas
by Chun Kit Chung, C. K. Law
We investigate the mean-field ground state of a homogeneous three-component attractive Fermi gas at zero temperature. This is achieved by deriving a set of Bogoliubov–de Gennes (BdG) equations of the three-component system, including pairing both order parameters $Δ_{ij}$ and coherence order parameters $〈 ψ_{i}^{†} ψ_{j} 〉$ ( $i \neq j$ ), where $ψ_{j}$ is the field operator for spin level $j$ . Ward-Takahashi identities are obtained to constrain these order parameters. In addition, we present an explicit analytic mean-field solution for symmetric systems and verify that the quasiparticle excitations consist of both gapped and gapless spectra, which correspond to the excitations of paired and unpaired atoms. We further point out that the omission of $〈 ψ_{i}^{†} ψ_{j} 〉$ in BdG equations could lead to an overestimation of $Δ_{ij}$ in the strong coupling regime. DOI: http://dx.doi.org/10.1103/PhysRevA.82.033620 © 2010 The American Physical Society
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- 29 September 2010
- Published by American Physical Society (APS) in Physical Review A
Pairing and coherence order parameters in a three-component ultracold Fermi gas
by Chun Kit Chung, C. K. Law
We investigate the mean-field ground state of a homogeneous three-component attractive Fermi gas at zero temperature. This is achieved by deriving a set of Bogoliubov–de Gennes (BdG) equations of the three-component system, including pairing both order parameters $Δ_{ij}$ and coherence order parameters $〈 ψ_{i}^{†} ψ_{j} 〉$ ( $i \neq j$ ), where $ψ_{j}$ is the field operator for spin level $j$ . Ward-Takahashi identities are obtained to constrain these order parameters. In addition, we present an explicit analytic mean-field solution for symmetric systems and verify that the quasiparticle excitations consist of both gapped and gapless spectra, which correspond to the excitations of paired and unpaired atoms. We further point out that the omission of $〈 ψ_{i}^{†} ψ_{j} 〉$ in BdG equations could lead to an overestimation of $Δ_{ij}$ in the strong coupling regime. DOI: http://dx.doi.org/10.1103/PhysRevA.82.033620 © 2010 The American Physical Society
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- 13 April 2009
- Published by American Physical Society (APS) in Physical Review A
Short-time dynamics of an ultracold Fermi gas in radio-frequency spectroscopy
by Chun Kit Chung, C. K. Law
We employ a time-dependent variational approach to investigate the dynamics of a fermionic atomic gas driven by a radio-frequency (rf) field at zero temperature. Starting from an initial Bardeen-Cooper-Schrieffer (BCS) state with pairing of atoms of two internal levels, an rf field transfers atoms to a third level. Dynamical equations derived from the variational principle are shown to be consistent with the time-dependent Bogoliubov–de Gennes equation. In particular, we show that the short-time dynamics is governed by a set of linear equations, in which an eigenvector associated with a discrete eigenvalue can be identified as the formation of a pair bound state in the final scattering channel. Such a bound state induces characteristic oscillations in the time evolution of the order parameter. At longer times numerical solutions demonstrate complicated dynamics where linear theory breaks down.
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- 13 April 2009
- Published by American Physical Society (APS) in Physical Review A
Short-time dynamics of an ultracold Fermi gas in radio-frequency spectroscopy
by Chun Kit Chung, C. K. Law
We employ a time-dependent variational approach to investigate the dynamics of a fermionic atomic gas driven by a radio-frequency (rf) field at zero temperature. Starting from an initial Bardeen-Cooper-Schrieffer (BCS) state with pairing of atoms of two internal levels, an rf field transfers atoms to a third level. Dynamical equations derived from the variational principle are shown to be consistent with the time-dependent Bogoliubov–de Gennes equation. In particular, we show that the short-time dynamics is governed by a set of linear equations, in which an eigenvector associated with a discrete eigenvalue can be identified as the formation of a pair bound state in the final scattering channel. Such a bound state induces characteristic oscillations in the time evolution of the order parameter. At longer times numerical solutions demonstrate complicated dynamics where linear theory breaks down.
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- 12 September 2008
- Published by American Physical Society (APS) in Physical Review A
Negativity and momentum entanglement in Bardeen-Cooper-Schrieffer states at finite temperature
by Chun Kit Chung, C. K. Law
We analyze the momentum entanglement of homogeneous Bardeen–Cooper–Schrieffer (BCS) states between spin-up and spin-down particles at finite temperature. This is achieved by studying the structure of the partial transposition of the two-particle density matrix (denoted by $ρ_{2}^{T_{A}}$ ) in momentum space, as well as the corresponding negativity. We show that $ρ_{2}^{T_{A}}$ consists of infinitely many decoupled $2 \times 2$ submatrices, and momentum entanglement is a necessary and sufficient condition for a nonzero order parameter $Δ$ . From the distribution of eigenvalues of $ρ_{2}^{T_{A}}$ , we discover that momentum entanglement is most significantly contributed by pairs with momenta slightly above a surface related to the Fermi energy. In addition, we propose an entanglement witness operator for detecting momentum entanglement in BCS states.
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- 12 September 2008
- Published by American Physical Society (APS) in Physical Review A
Negativity and momentum entanglement in Bardeen-Cooper-Schrieffer states at finite temperature
by Chun Kit Chung, C. K. Law
We analyze the momentum entanglement of homogeneous Bardeen–Cooper–Schrieffer (BCS) states between spin-up and spin-down particles at finite temperature. This is achieved by studying the structure of the partial transposition of the two-particle density matrix (denoted by $ρ_{2}^{T_{A}}$ ) in momentum space, as well as the corresponding negativity. We show that $ρ_{2}^{T_{A}}$ consists of infinitely many decoupled $2 \times 2$ submatrices, and momentum entanglement is a necessary and sufficient condition for a nonzero order parameter $Δ$ . From the distribution of eigenvalues of $ρ_{2}^{T_{A}}$ , we discover that momentum entanglement is most significantly contributed by pairs with momenta slightly above a surface related to the Fermi energy. In addition, we propose an entanglement witness operator for detecting momentum entanglement in BCS states.
Cited by 8