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Title | : Quantifying the Heat Dissipation from a Molecular Motors Transport Properties in Nonequilibrium Steady States |
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Author | : Wonseok Hwang, Changbong Hyeon |
Journal | : The Journal of Physical Chemistry Letters |
NUMBER | C17002 |
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AUTHOR | Wonseok Hwang, Changbong Hyeon |
TITLE | Quantifying the Heat Dissipation from a Molecular Motors Transport Properties in Nonequilibrium Steady States |
ARCHIVE | arXiv:1612.05747v2 |
FILE | |
JOURNAL | The Journal of Physical Chemistry Letters |
ABSTRACT | Theoretical analysis, which maps single molecule time trajectories of a molecular motor onto unicyclic Markov processes, allows us to evaluate the heat dissipated from the motor and to elucidate its dependence on the mean velocity and diffusivity. Unlike passive Brownian particles in equilibrium, the velocity and diffusion constant of molecular motors are closely inter-related to each other. In particular, our study makes it clear that the increase of diffusivity with the heat production is a natural outcome of active particles, which is reminiscent of the recent experimental premise that the diffusion of an exothermic enzyme is enhanced by the heat released from its own catalytic turnover. Compared with freely diffusing exothermic enzymes, kinesin-1 whose dynamics is confined on one-dimensional tracks is highly efficient in transforming conformational fluctuations into a locally directed motion, thus displaying a significantly higher enhancement in diffusivity with its turnover rate. Putting molecular motors and freely diffusing enzymes on an equal footing, our study offers thermodynamic basis to understand the heat enhanced self-diffusion of exothermic enzymes. |
Title | : Decoding Single Molecule Time Traces with Dynamic Disorder |
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Author | : Wonseok Hwang, Il-Buem Lee, Seok-Cheol Hong, Changbong Hyeon |
Journal | : Plos Computational Biology |
NUMBER | C17001 |
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AUTHOR | Wonseok Hwang, Il-Buem Lee, Seok-Cheol Hong, Changbong Hyeon |
TITLE | Decoding Single Molecule Time Traces with Dynamic Disorder |
ARCHIVE | arXiv:1612.04514 |
FILE | |
JOURNAL | Plos Computational Biology |
ABSTRACT | Single molecule time trajectories of biomolecules provide glimpses into complex folding landscapes that are difficult to visualize using conventional ensemble measurements. Recent experiments and theoretical analyses have highlighted dynamic disorder in certain classes of biomolecules, whose dynamic pattern of conformational transitions is affected by slower transition dynamics of internal state hidden in a low dimensional projection. A systematic means to analyze such data is, however, currently not well developed. Here we report a new algorithm - Variational Bayes-double chain Markov model (VB- DCMM) - to analyze single molecule time trajectories that display dynamic disorder. The proposed analysis employing VB-DCMM allows us to detect the presence of dynamic disorder, if any, in each trajectory, identify the number of internal states, and estimate transition rates between the internal states as well as the rates of conformational transition within each internal state. Applying VB-DCMM algorithm to single molecule FRET data of H-DNA in 100 mM-Na+ solution, followed by data clustering, we show that at least 6 kinetic paths linking 4 distinct internal states are required to correctly interpret the duplex-triplex transitions of H-DNA. |
Title | : Comment on ¡°Quasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor Surfaces¡± |
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Author | : Sun-Woo Kim, Yoon-Gu Kang, Hyun-Jung Kim, Jun-Hyung Cho |
Journal | : Phys. Rev. Lett. 118, 239601 (2017) |
NUMBER | C17005 |
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AUTHOR | Sun-Woo Kim, Yoon-Gu Kang, Hyun-Jung Kim, Jun-Hyung Cho |
TITLE | Comment on ¡°Quasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor Surfaces¡± |
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FILE | |
JOURNAL | Phys. Rev. Lett. 118, 239601 (2017) |
ABSTRACT |
Title | : Origins of the structural phase transitions in MoTe2 and WTe2 |
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Author | : Hyun-Jung Kim, Seoung-Hun Kang, Ikutaro Hamada, Young-Woo Son |
Journal | : Physical Review B 95, 180101(R) (2017) |
NUMBER | C17004 |
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AUTHOR | Hyun-Jung Kim, Seoung-Hun Kang, Ikutaro Hamada, Young-Woo Son |
TITLE | Origins of the structural phase transitions in MoTe2 and WTe2 |
ARCHIVE | cond-mat/1702.04509 |
FILE | PhysRevB.95.180101 (2017) Origins of the structural phase transitions in MoTe2 and WTe2.pdf |
JOURNAL | Physical Review B 95, 180101(R) (2017) |
ABSTRACT | Layered transition metal dichalcogenides MoTe2 and WTe2 share almost similar lattice constants as well as topological electronic properties except their structural phase transitions. While the former shows a first-order phase transition between monoclinic and orthorhombic structures, the latter does not. Using a recently proposed van der Waals density functional method, we investigate structural stability of the two materials and uncover that the disparate phase transitions originate from delicate differences between their interlayer bonding states near the Fermi energy. By exploiting the relation between the structural phase transitions and the low energy electronic properties, we show that a charge doping can control the transition substantially, thereby suggesting a way to stabilize or to eliminate their topological electronic energy bands. |
Title | : Contrasting diffusion behaviors of O and F atoms on graphene and within bilayer graphene |
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Author | : Seho Yi, Jin-Ho Choi, Hyun-Jung Kim, Chul Hong Park, Jun-Hyung Cho |
Journal | : Physical Chemistry Chemical Physics |
NUMBER | C17003 |
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AUTHOR | Seho Yi, Jin-Ho Choi, Hyun-Jung Kim, Chul Hong Park, Jun-Hyung Cho |
TITLE | Contrasting diffusion behaviors of O and F atoms on graphene and within bilayer graphene |
ARCHIVE | cond-mat/1611.08390 |
FILE | PCCP.19.9107 (2017) Contrasting diffusion behaviors of O and F atoms on graphene and within bilayer graphene.pdf |
JOURNAL | Physical Chemistry Chemical Physics |
ABSTRACT | Chemical modification of graphene with adatoms is of importance for nanoelectronics applications. Based on first-principles density-functional theory calculations including van der Waals interactions, we present a comparative study of the diffusion characteristics of oxygen (O) and fluorine (F) atoms both on graphene and between the layers of bilayer graphene. We find that the calculated diffusion barrier for the O atom increases slightly from 0.81 eV on graphene to 0.85 eV within bilayer graphene, while that for the F atom largely decreases from 0.30 eV on graphene to 0.18 eV within bilayer graphene. Such contrasting behaviors of the O and F diffusions within bilayer graphene can be traced to their different bonding natures: i.e., the O adatom that shows strongly covalent C–O– C bonding on the bridge site of the C–C bond diffuses on one graphene layer with a slight interference of the other layer, while the F adatom that shows semi-ionic F–C bonding on top of a C atom easily diffuses by hopping between two graphene layers by accepting more electron charges from the two layers. The present findings have important implications for the understanding of the diffusion processes of F and O atoms on graphene and within bilayer graphene. |
Title | : Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111) |
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Author | : Xiao-Yan Ren, Hyun-Jung Kim, Seho Yi, Yu Jia, Jun-Hyung Cho |
Journal | : Physical Review B 94, 075436 (2016) |
NUMBER | C16001 |
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AUTHOR | Xiao-Yan Ren, Hyun-Jung Kim, Seho Yi, Yu Jia, Jun-Hyung Cho |
TITLE | Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111) |
ARCHIVE | arXiv:1606.04208 |
FILE | PhysRevB.94.075436 (2016) Spin-orbit coupling effects on the stability of two competing structures in Pb:Si(111) and Pb:Ge(111).pdf |
JOURNAL | Physical Review B 94, 075436 (2016) |
ABSTRACT | Using first-principles density-functional theory (DFT) calculations with/without including the spin- orbit coupling (SOC), we systematically investigate the (4/3)-monolayer structure of Pb on the Si(111) or Ge(111) surface within the two competing structural models termed the H3 and T4 structures. We find that the SOC influences the relative stability of the two structures in both the Pb/Si(111) and the Pb/Ge(111) systems, i.e., our DFT calculation without including the SOC predicts that the T4 structure is energetically favored over the H3 structure by E = 25 meV for Pb/Si(111) and 22 meV for Pb/Ge(111), but the inclusion of SOC reverses their relative stability as E = −12 and −7 meV, respectively. Our analysis shows that the SOC-induced switching of the ground state is attributed to a more asymmetric surface charge distribution in the H3 structure compared to the T4 structure, which is associated with the hybridization of the Pb px , py , and pz orbitals. This asymmetry of surface charge distribution gives rise to a relatively larger Rashba spin splitting of surface states as well as a relatively larger pseudogap opening in the H3 structure. By the nudged elastic-band calculation, we obtain a sizable energy barrier from the H3 to the T4 structure as ~0.59 and ~0.27 eV for Pb/Si(111) and Pb/Ge(111), respectively. Based on the predicted thermodynamics and kinetics of Pb/Si(111) and Pb/Ge(111), we suggest not only the coexistence of the two energetically competing structures at low temperatures, but also the order- disorder transition at high temperatures. |
Title | : Origin of Symmetric Dimer Images of Si (001) Observed in Low-Temperature STM |
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Author | : Xiao-Yan Ren, Hyun-Jung Kim, Chun-Yao Niu, Yu Jia, Jun-Hyung Cho |
Journal | : Sci.Rep. 6, 27868 (2016) |
NUMBER | C15020 |
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AUTHOR | Xiao-Yan Ren, Hyun-Jung Kim, Chun-Yao Niu, Yu Jia, Jun-Hyung Cho |
TITLE | Origin of Symmetric Dimer Images of Si (001) Observed in Low-Temperature STM |
ARCHIVE | 1510.05406 |
FILE | Sci.Rep.6.27868 (2016) Origin of Symmetric Dimer Images of Si(001) Observed by LT STM.pdf |
JOURNAL | Sci.Rep. 6, 27868 (2016) |
ABSTRACT | It has been a long-standing puzzle why buckled dimers of the Si(001) surface appeared symmetric below 20 K in scanning tunneling microscopy (STM) experiments. Although such symmetric dimer images were concluded to be due to an artifact induced by STM measurements, its underlying mechanism is still veiled. Here,we demonstrate, based on a first-principles density-functional theory calculation, that the symmetric dimer images are originated from the flip-flop motion of buckled dimers, driven by quantum tunneling (QT). It is revealed that at low temperature the tunneling- induced surface charging with holes reduces the energy barrier for the flipping of buckled dimers, thereby giving rise to a sizable QT-driven frequency of the flip-flop motion. However, such a QT phenomenon becomes marginal in the tunneling-induced surface charging with electrons. Our findings provide an explanation for low-temperature STM data that exhibits apparent symmetric (buckled) dimer structure in the filled-state (empty-state) images. |
Title | : Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices |
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Author | : Hyun-Jung Kim, Chaokai Li, Ji Feng, Jun-Hyung Cho, Zhenyu Zhang |
Journal | : PHYSICAL REVIEW B 93, 041404(R) (2016) |
NUMBER | C15019 |
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AUTHOR | Hyun-Jung Kim, Chaokai Li, Ji Feng, Jun-Hyung Cho, Zhenyu Zhang |
TITLE | Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices |
ARCHIVE | |
FILE | |
JOURNAL | PHYSICAL REVIEW B 93, 041404(R) (2016) |
ABSTRACT | The exploration of topological states is of significant fundamental and practical importance in contemporary condensed matter physics, for which the extension to two-dimensional (2D) organometallic systems is particularly attractive. Using first-principles calculations, we show that a 2D hexagonal triphenyl-lead lattice composed of only main group elements is susceptible to a magnetic instability, characterized by a considerably more stable antiferromagnetic (AFM) insulating state rather than the topologically nontrivial quantum spin Hall state proposed recently. Even though this AFM phase is topologically trivial, it possesses an intricate emergent degree of freedom, defined by the product of spin and valley indices, leading to Berry curvature-induced spin and valley currents under electron or hole doping. Furthermore, such a trivial band insulator can be tuned into a topologically nontrivial matter by the application of an out-of-plane electric field, which destroys the AFM order, favoring instead ferrimagnetic spin ordering and a quantum anomalous Hall state with a non-zero topological invariant. These findings further enrich our understanding of 2D hexagonal organometallic lattices for potential applications in spintronics and valleytronics. |
Title | : Giant spin-orbit-induced spin splitting in Bi zigzag chains on GaAs(110) |
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Author | : Hyun-Jung Kim, Jun-Hyung Cho |
Journal | : PHYSICAL REVIEW B 92, 085303 (2015) |
NUMBER | C15018 |
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AUTHOR | Hyun-Jung Kim, Jun-Hyung Cho |
TITLE | Giant spin-orbit-induced spin splitting in Bi zigzag chains on GaAs(110) |
ARCHIVE | |
FILE | PhysRevB.92.085303 (2015) Giant spin-orbit-induced spin splitting in Bi zigzag chains on GaAs(110).pdf |
JOURNAL | PHYSICAL REVIEW B 92, 085303 (2015) |
ABSTRACT | The search for one-dimensional electron systems with a giant Rashba-type spin splitting is of importance for the application of spin transport. Here we report, based on a first-principles density- functional-theory calculation, that Bi zigzag chains formed on a heterogeneous GaAs(110) surface have a giant spin splitting of surface states. This giant spin splitting is revealed to originate from spin-orbit coupling (SOC) and electric dipole interaction that are significantly enhanced by (i) the asymmetric surface charge distribution due to the strong SOC-induced hybridization of the Bi px , py , and pz orbitals and (ii) the large out-of-plane and in-plane potential gradients generated by two geometrically and electronically inequivalent Bi atoms bonding to Ga and As atoms. The results demonstrate an important implication of the in-plane and out-of-plane asymmetry of the Bi/GaAs(110) interface system in producing the giant spin splitting with the in-plane and out-of- plane spin components. |
Title | : Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3 |
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Author | : Sun-Woo Kim, Chen Liu, Hyun-Jung Kim, Jun-Ho Lee, Yongxin Yao, Kai-Ming Ho, Jun-Hyung Cho |
Journal | : Phys. Rev. Lett. 115, 096401 (2015) |
NUMBER | C15017 |
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AUTHOR | Sun-Woo Kim, Chen Liu, Hyun-Jung Kim, Jun-Ho Lee, Yongxin Yao, Kai-Ming Ho, Jun-Hyung Cho |
TITLE | Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3 |
ARCHIVE | |
FILE | PhysRevLett.115.096401 (2015) Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3.pdf |
JOURNAL | Phys. Rev. Lett. 115, 096401 (2015) |
ABSTRACT | The insulating ground state of the 5d transition metal oxide CaIrO3 has been classified as a Mott- type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange-correlation functionals, we reveal that the Ir t2g states exhibit large splittings and one-dimensional electronic states along the c axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the c direction via a superexchange interaction between Ir4© spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the t2g states to open an insulating gap. These results indicate that CaIrO3 can be represented as a spin-orbit Slater insulator, driven by the interplay between a long-range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT + dynamical mean field theory calculation, where the metal- insulator transition and the paramagnetic to AFM phase transition are concomitant with each other. |
Title | : Macroscopic Entangled States in Superconducting Flux Qubits |
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Author | : Mun Dae Kim, Sam Young Cho |
Journal | : Journal of Physics: Conference Series |
NUMBER | P08044 |
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AUTHOR | Mun Dae Kim, Sam Young Cho |
TITLE | Macroscopic Entangled States in Superconducting Flux Qubits |
ARCHIVE | |
FILE | LT2996_entangle.pdf |
JOURNAL | Journal of Physics: Conference Series |
ABSTRACT | We theoretically study the macroscopic quantum entanglement in superconducting flux qubits. A phase-coupling scheme is proposed to offer enough strength of interactions between qubits. It is shown that due to the two-qubit tunneling processes both the ground state and excited states of coupled two flux qubits can be Bell type states, maximally entangled, in experimentally accessible regimes. The parameter regimes for the Bell states are discussed in terms of external magnetic flux and Josephson coupling energies. We also investigate two types of genuine three-qubit entanglement, known as the Greenberger-Horne- Zeilinger(GHZ) and W states. While an excited state can be the W state, the GHZ state is formed at the ground state of the coupled three flux qubits. The GHZ and W states are shown to be robust against external flux fluctuations for feasible experimental realizations. |
Title | : Coherent Operation of Superconducting Flux Qubits at Optimal Point |
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Author | : Mun Dae Kim, Sam Young Cho |
Journal | : |
NUMBER | P08035 |
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AUTHOR | Mun Dae Kim, Sam Young Cho |
TITLE | Coherent Operation of Superconducting Flux Qubits at Optimal Point |
ARCHIVE | |
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JOURNAL | |
ABSTRACT | We study microwave-driven quantum coherent operations of superconducting flux qubits. The interaction between the threading microwave flux and the qubits is shown to be described in terms of magnetic dipole energy of qubit current states. The discriminating Rabi oscillation for the controlled-NOT gate operation requires a strong coupling which is obtainable using a phase-coupling scheme. We also discuss how the coupled-qubit operations can be performed at the optimal point. |
Title | : Superconducting-ferromagnet Junction Phase Qubit |
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Author | : Tae-Wan Noh, Mun Dae Kim, Heung-Sun Sim |
Journal | : |
NUMBER | P08010 |
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AUTHOR | Tae-Wan Noh, Mun Dae Kim, Heung-Sun Sim |
TITLE | Superconducting-ferromagnet Junction Phase Qubit |
ARCHIVE | 0804.0349 |
FILE | |
JOURNAL | |
ABSTRACT | We propose a new phase qubit in an SIFIS junction, consisting of bulk superconductors (S), a ferromagnet (F), and insulating barriers (I). The qubit state is constituted by the 0 and the $pi$ phase states of the junction, in which the charging energy of the barriers leads to the superposition of the two states. The qubit is operated by the gate voltage applied to the ferromagnet, and insensitive to the decoherences existing in other superconducting qubits. We discuss a scalable scheme for qubit measurement and tunable two-qubit coupling. |
Title | : Kondo physics in the algebraic spin liquid |
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Author | : Ki-Seok Kim, Mun Dae Kim |
Journal | : J. Phys.: Condens. Matter 20 (2008) 125206 |
NUMBER | P07033 |
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AUTHOR | Ki-Seok Kim, Mun Dae Kim |
TITLE | Kondo physics in the algebraic spin liquid |
ARCHIVE | 0706.2943 |
FILE | |
JOURNAL | J. Phys.: Condens. Matter 20 (2008) 125206 |
ABSTRACT | We study Kondo physics in the algebraic spin liquid, recently proposed t o describe $ZnCu_{3}(OH)_{6}Cl_{2}$ [Phys. Rev. Lett. {bf 98}, 1 17205 (2007)]. Although the spin dynamics of the algebraic spin liquid is d escribed by massless Dirac fermions, this problem differs from the P seudogap Kondo model, because the bulk physics in the algebraic spin l iquid is governed by an interacting fixed point where well-defined q uasiparticle excitations are not allowed. Considering an effective bulk m odel characterized by an anomalous critical exponent, we derive an e ffective impurity action in the slave-boson context. Performing the large-$ N_{sigma}$ analysis with a spin index $N_{sigma}$, we find an i mpurity quantum phase transition from a decoupled local-moment state to a Kondo-screened phase. We evaluate the impurity spin susceptibility a nd specific heat coefficient at zero temperature, and find that such r esponses follow power-law dependencies modified by the anomalous e xponent of the algebraic spin liquid. Our main finding is that the Wilsons r atio for the magnetic impurity depends strongly on the critical exponent in t he zero temperature limit. We propose that the Wilsons ratio for the m agnetic impurity may be one possible probe to reveal criticality of the b ulk system. |
Title | : Spin-gapped incoherent metal with preformed pairing in the doped antiferromagnetic Mott insulator |
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Author | : Ki-Seok Kim, Mun Dae Kim |
Journal | : Physical Review B 77, 125103 (2008) |
NUMBER | P07032 |
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AUTHOR | Ki-Seok Kim, Mun Dae Kim |
TITLE | Spin-gapped incoherent metal with preformed pairing in the doped antiferromagnetic Mott insulator |
ARCHIVE | 0702586 |
FILE | |
JOURNAL | Physical Review B 77, 125103 (2008) |
ABSTRACT | We investigate how the antiferromagnetic Mott insulator (AF-MI) evolves i nto the high $T_{c}$ superconductor (HTc-SC) through hole doping. A llowing spin fluctuations in the strong coupling approach, we find a s pin-gapped incoherent metal with preformed pairing as an intermediate p hase between the AF-MI and HTc-SC. This non-Fermi liquid metal is i dentified with an infrared stable fixed point in the spin-decomposition g auge theory, analogous to the spin liquid insulator in the slave-boson g auge theory. We discuss how its presence can explain that onset of s uperconductivity results in coherence of elementary excitations. |
Title | : Realizable spin models and entanglement dynamics in superconducting flux qubit systems |
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Author | : Qian Qian Shi, Sam Young Cho, Bo Li, Mun Dae Kim |
Journal | : Physical Review B 77, 104511 (2008) |
NUMBER | P07028 |
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AUTHOR | Qian Qian Shi, Sam Young Cho, Bo Li, Mun Dae Kim |
TITLE | Realizable spin models and entanglement dynamics in superconducting flux qubit systems |
ARCHIVE | 0706.2402 |
FILE | |
JOURNAL | Physical Review B 77, 104511 (2008) |
ABSTRACT | Realizable spin models are investigated in a two superconducting flux qubit system. It is shown that a specific adjustment of system parameters in the two flux qubit system makes it possible to realize an artificial two- spin system that cannot be found naturally. For the artificial two-spin systems, time evolution of a prepared quantum state is discussed to quantify quantum entanglement dynamics. The concurrence and fidelity as a function of time are shown to reveal a characteristic entanglement dynamics of the artificial spin systems. It is found that the unentangled input state can evolute to be a maximally entangled output state periodically due to the exchange interactions induced by two-qubit flipping tunneling processes while single-qubit flipping tunneling processes plays a role of magnetic fields for the artificial spins. |
Title | : Macroscopic Greenberger-Horne-Zeilinger and W States in Flux Qubits |
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Author | : Mun Dae Kim, Sam Young Cho |
Journal | : Physical Review B 77, 100508(R) (2008) |
NUMBER | P07024 |
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AUTHOR | Mun Dae Kim, Sam Young Cho |
TITLE | Macroscopic Greenberger-Horne-Zeilinger and W States in Flux Qubits |
ARCHIVE | arXiv:0705.3391 |
FILE | |
JOURNAL | Physical Review B 77, 100508(R) (2008) |
ABSTRACT | We investigate two types of genuine three-qubit entanglement, known as the Greenberger-Horne-Zeilinger (GHZ) and W states, in a macroscopic quantum system. Superconducting flux qubits are considered theoretically in order to generate such states. A phase coupling is proposed in a way of superconducting loops connecting the qubits, which can offer enough strength of interactions between qubits. While an excited state can be the W state, the ground state of the three-flux qubits is shown to be the GHZ state. Specific ranges of system parameters are discussed to realize the GHZ state and the W state experimentally. |
Title | : Macroscopic Many-Qubit Interactions in Superconducting Flux Qubits |
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Author | : Sam Young Cho, Mun Dae Kim |
Journal | : Physical Review B 77, 212506 (2008) |
NUMBER | P07023 |
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AUTHOR | Sam Young Cho, Mun Dae Kim |
TITLE | Macroscopic Many-Qubit Interactions in Superconducting Flux Qubits |
ARCHIVE | 0703505 |
FILE | |
JOURNAL | Physical Review B 77, 212506 (2008) |
ABSTRACT | Superconducting flux qubits are considered to investigate macroscopic many-qubit interactions. Many-qubit states based on current states can be manipulated through the current-phase relation in each superconducting loop. For flux qubit systems comprised of $N$ qubit loops, a general expression of low energy Hamiltonian is presented in terms of low energy levels of qubits and macroscopic quantum tunnelings between the many- qubit states. Many-qubit interactions classified by {em Ising type- or tunnel-} exchange interactions can be observable experimentally. Flux qubit systems can provide various artificial-spin systems to study many-body systems that cannot be found naturally. |
Title | : Antiferromagnetic metal to heavy-fermion metal quantum phase transition in the Kondo lattice model: A strong-coupling approach |
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Author | : Ki-Seok Kim, Mun Dae Kim |
Journal | : Phys. Rev. B vol. 75, 035117 (2007) |
NUMBER | P07003 |
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AUTHOR | Ki-Seok Kim, Mun Dae Kim |
TITLE | Antiferromagnetic metal to heavy-fermion metal quantum phase transition in the Kondo lattice model: A strong-coupling approach |
ARCHIVE | cond-mat/0608235 |
FILE | |
JOURNAL | Phys. Rev. B vol. 75, 035117 (2007) |
ABSTRACT |
Title | : Entanglement and Bell States in Superconducting Flux Qubits |
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Author | : Mun Dae Kim, Sam Young Cho |
Journal | : Physical Review B 75, 134514 (2007) |
NUMBER | P06007 |
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AUTHOR | Mun Dae Kim, Sam Young Cho |
TITLE | Entanglement and Bell States in Superconducting Flux Qubits |
ARCHIVE | cond-mat/0606034 |
FILE | |
JOURNAL | Physical Review B 75, 134514 (2007) |
ABSTRACT | We theoretically study macroscopic quantum entanglement in two superconducting flux qubits. To manipulate the state of two flux qubits, a Josephson junction is introduced in the connecting loop coupling the qubits. Increasing the coupling energy of the Josephson junction makes it possible to achieve relatively strong coupling between the qubits, causing two-qubit tunneling processes even dominant over the single-qubit tunneling process in the states of two qubits. It is shown that due to the two-qubit tunneling processes both the ground state and excited state of the coupled flux qubits can be a Bell type state, maximally entangled. The parameter regimes for the Bell states are discussed in terms of magnetic flux and Josephson coupling energies. |
Title | : Controllable Coupling in Phase-Coupled Flux Qubits |
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Author | : Mun Dae Kim |
Journal | : PHYSICAL REVIEW B 74 (18): Art. No. 184501 NOV 2006 |
NUMBER | P06006 |
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AUTHOR | Mun Dae Kim |
TITLE | Controllable Coupling in Phase-Coupled Flux Qubits |
ARCHIVE | cond-mat/0602604 |
FILE | |
JOURNAL | PHYSICAL REVIEW B 74 (18): Art. No. 184501 NOV 2006 |
ABSTRACT | We suggest a scheme for controllable coupling of the phase-coupled flux qubits, where a connecting loop is introduced to couple the phase differences of Josephson junctions in different qubits. Two dc-SQUIDs with penetrating fluxes of opposite directions are inserted into the connecting loop and by varying the fluxes we can achieve a broad range of coupling from sufficiently strong to vanishing in switching-off limit. |
Title | : Current-phase relation of the SNS junction in a superconducting loop |
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Author | : Mun Dae Kim, Jongbae Hong |
Journal | : EUROPHYSICS LETTERS 73 (1): 90-96 JAN 2006 |
NUMBER | P05073 |
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AUTHOR | Mun Dae Kim, Jongbae Hong |
TITLE | Current-phase relation of the SNS junction in a superconducting loop |
ARCHIVE | cond-mat/0406445 |
FILE | |
JOURNAL | EUROPHYSICS LETTERS 73 (1): 90-96 JAN 2006 |
ABSTRACT | We study the current-phase relation of the superconductor/normal/superconductor (SNS) junction imbedded in a superconducting loop. Considering the current conservation and free energy minimum conditions, we obtain the persistent currents of the SNS loop. At finite temperature we can explain the experimentally observed highly non-sinusoidal currents which have maxima near the zero external flux. |
Title | : Effect of the Andreev reflection phase shift on the currents of SNS junctions and NS loops |
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Author | : Mun Dae Kim, Jongbae Hong |
Journal | : J. Korean Phys. Soc. 46, 689 (2005) |
NUMBER | P04056 |
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AUTHOR | Mun Dae Kim, Jongbae Hong |
TITLE | Effect of the Andreev reflection phase shift on the currents of SNS junctions and NS loops |
ARCHIVE | |
FILE | |
JOURNAL | J. Korean Phys. Soc. 46, 689 (2005) |
ABSTRACT | We study the effect of the phase shift, $eta$, of the electron wave function due to the Andreev reflection process on the currents of superconducting/normal/superconducting (SNS) junctions and of normal/superconducting (NS) loops with an Aharonov-Bohm flux. We show that the current conservation condition is crucial in obtaining the currents of the SNS junctions and the NS loops. The persistent currents of NS loop shows the periodicity of the superconducting unit flux quantum, $Phi_0/2$, regardless of the length of the normal sector or the superconducting sector, when the energy splitting $E$ is smaller than the pair potential $Delta$. In the limit, $Ell Delta$, we obtain a Josephson type formula, $Ipropto sqrt{Delta}sin (pi/2-2eta)$, by minimizing the free energy of the NS loop. |
Title | : Diamagnetic Response of Aharonov-Bohm Rings: Impurity Backward Scatterings |
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Author | : Mun Dae Kim, Chul Koo Kim, Kyun Nahm |
Journal | : PHYSICAL REVIEW B 72 (8): Art. No. 085333 AUG 2005 |
NUMBER | P04055 |
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AUTHOR | Mun Dae Kim, Chul Koo Kim, Kyun Nahm |
TITLE | Diamagnetic Response of Aharonov-Bohm Rings: Impurity Backward Scatterings |
ARCHIVE | cond-mat/0412189 |
FILE | |
JOURNAL | PHYSICAL REVIEW B 72 (8): Art. No. 085333 AUG 2005 |
ABSTRACT |
Title | : Nature of the Insulating Ground State in 5d Postperovskite CaIrO3 |
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Author | : Sun-Woo Kim, Chen Liu, Hyun-Jung Kim, Jun-Ho Lee, Yongxin Yao, Kai-Ming Ho, Jun-Hyung Cho |
Journal | : Phys. Rev. Lett. 115, 096401 (2015) |
NUMBER | C15016 |
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AUTHOR | Sun-Woo Kim, Chen Liu, Hyun-Jung Kim, Jun-Ho Lee, Yongxin Yao, Kai-Ming Ho, Jun-Hyung Cho |
TITLE | Nature of the Insulating Ground State in 5d Postperovskite CaIrO3 |
ARCHIVE | arXiv:1501.01762 |
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JOURNAL | Phys. Rev. Lett. 115, 096401 (2015) |
ABSTRACT | The insulating ground state of the 5d transition metal oxide CaIrO3 has been classified as a Mott-type insulator. Based on a systematic density functional theory (DFT) study with local, semilocal, and hybrid exchange- correlation functionals, we reveal that the Ir t2g states exhibit large splittings and one- dimensional electronic states along the c axis due to a tetragonal crystal field. Our hybrid DFT calculation adequately describes the antiferromagnetic (AFM) order along the c direction via a superexchange interaction between Ir4+ spins. Furthermore, the spin-orbit coupling (SOC) hybridizes the t2g states to open an insulating gap. These results indicate that CaIrO3 can be represented as a spin-orbit Slater insulator, driven by the interplay between a long- range AFM order and the SOC. Such a Slater mechanism for the gap formation is also demonstrated by the DFT + dynamical mean field theory calculation, where the metal- insulator transition and the paramagnetic to AFM phase transition are concomitant with each other. |
Title | : Antiferromagnetic superexchange mediated by a resonant surface state in Sn/Si(111) |
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Author | : Jun-Ho Lee, Xiao-Yan Ren, Yu Jia, Jun-Hyung Cho |
Journal | : Phys. Rev. B 90, 125439 (2014) |
NUMBER | C14006 |
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AUTHOR | Jun-Ho Lee, Xiao-Yan Ren, Yu Jia, Jun-Hyung Cho |
TITLE | Antiferromagnetic superexchange mediated by a resonant surface state in Sn/Si(111) |
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JOURNAL | Phys. Rev. B 90, 125439 (2014) |
ABSTRACT | The Sn overlayer on the Si(111) surface has been considered as a prototypical system for exploring two dimensional (2D) correlated physics on the triangular lattice. Most of the previous theoretical studies were based on the presumption that the surface state dominantly originates from Sn dangling-bond (DB) electrons, leading to a strongly correlated 2D electronic system. By contrast, our density-functional theory calculations show that the Sn DB state significantly hybridizes with Si substrate states to form a resonant state. The strong resonance between the Sn 5p_z and Si 3p_z orbitals facilitates the recently observed antiferromagnetic order through superexchange interactions, giving rise to a band-gap opening. It is thus demonstrated that the insulating ground state of Sn/Si(111) can be characterized as a Slater- type insulator via band magnetism. |