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- Baik, Seung Su
- KIAS Assistant Professor
- Theoretical and Computational Condensed Matter Physics
- Office : 1526
- Tel : 3898 | Fax : 3870
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- Jo, Junghyo
- KIAS Assistant Professor
- Computational Biology
- Office : 7309-5
- Tel : 3850 | Fax :
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- Hwang, Wonseok
- Research Fellow
- Computational Biophysics
- Office : 7312
- Tel : 3863 | Fax : 3820
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Quantifying the Heat Dissipation from a Molecular Motors Transport Properties in Nonequilibrium Steady States Title : Quantifying the Heat Dissipation from a Molecular Motors Transport Properties in Nonequilibrium Steady States Author : Wonseok Hwang, Changbong Hyeon Journal : The Journal of Physical Chemistry Letters
Quantifying the Heat Dissipation from a Molecular Motors Transport Properties in Nonequilibrium Steady States NUMBER C17002 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.
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Decoding Single Molecule Time Traces with Dynamic Disorder Title : Decoding Single Molecule Time Traces with Dynamic Disorder Author : Wonseok Hwang, Il-Buem Lee, Seok-Cheol Hong, Changbong Hyeon Journal : Plos Computational Biology
Decoding Single Molecule Time Traces with Dynamic Disorder NUMBER C17001 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.
- Bak, Ji Hyun
- Research Fellow
- Theoretical and Computational Biophysics
- Office : 7321
- Tel : 3814 | Fax : 3820
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Adaptive optimal training of animal behavior Title : Adaptive optimal training of animal behavior Author : Ji Hyun Bak, Jung Yoon Choi, Athena Akrami, Ilana Witten, Jonathan W Pillow Journal : Advances in Neural Information Processing Systems 29 (NIPS 2016)
Adaptive optimal training of animal behavior NUMBER C17017 AUTHOR Ji Hyun Bak, Jung Yoon Choi, Athena Akrami, Ilana Witten, Jonathan W Pillow TITLE Adaptive optimal training of animal behavior ARCHIVE FILE JOURNAL Advances in Neural Information Processing Systems 29 (NIPS 2016) ABSTRACT
- Bang, Jeongho
- Research Fellow
- Quantum Information
- Office : 7313
- Tel : 3807 | Fax :
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- Chae, Kisung
- Research Fellow
- Theoretical and Computational Materials Science
- Office : 1524
- Tel : 3897 | Fax : 3870
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- Flores-Canales, Jose
- Research Fellow
- Protein Folding
- Office : 7315
- Tel : 2643 | Fax : 3820
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- Heo, Seungryong
- Research Fellow
- Protein Structure Prediction
- Office :
- Tel : | Fax :
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- Hong, Seung Hwan
- Research Fellow
- Protein Folding
- Office : 7315
- Tel : 2642 | Fax :
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- Hyun, Jong Yoon
- Research Fellow
- Combinatorics, Algebraic and Combinatorial Coding Theory
- Office : 1327
- Tel : 3719 | Fax : 3870
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- Kang, Seoung-Hun
- Research Fellow
- Theoretical and Computational Materials Science
- Office : 1517
- Tel : 3856 | Fax :
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- Kim, Hyun-Jung
- Research Fellow
- Theoretical and Computational Materials Science
- Office : 1534
- Tel : 2534 | Fax : 3870
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Microscopic mechanism of the tunable band gap in potassium-doped few-layer black phosphorus Title : Microscopic mechanism of the tunable band gap in potassium-doped few-layer black phosphorus Author : Sun-Woo Kim, Hyun Jung, Hyun-Jung Kim, Jin-Ho Choi, Su-Huai Wei, Jun-Hyung Cho Journal : PHYSICAL REVIEW B
Microscopic mechanism of the tunable band gap in potassium-doped few-layer black phosphorus NUMBER C17015 AUTHOR Sun-Woo Kim, Hyun Jung, Hyun-Jung Kim, Jin-Ho Choi, Su-Huai Wei, Jun-Hyung Cho TITLE Microscopic mechanism of the tunable band gap in potassium-doped few-layer black phosphorus ARCHIVE FILE JOURNAL PHYSICAL REVIEW B ABSTRACT
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Comment on ¡°Quasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor Surfaces¡± Title : Comment on ¡°Quasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor Surfaces¡± Author : Sun-Woo Kim, Yoon-Gu Kang, Hyun-Jung Kim, Jun-Hyung Cho Journal : Phys. Rev. Lett. 118, 239601 (2017)
Comment on ¡°Quasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor Surfaces¡± NUMBER C17005 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¡± ARCHIVE FILE JOURNAL Phys. Rev. Lett. 118, 239601 (2017) ABSTRACT
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Origins of the structural phase transitions in MoTe2 and WTe2 Title : Origins of the structural phase transitions in MoTe2 and WTe2 Author : Hyun-Jung Kim, Seoung-Hun Kang, Ikutaro Hamada, Young-Woo Son Journal : Physical Review B 95, 180101(R) (2017)
Origins of the structural phase transitions in MoTe2 and WTe2 NUMBER C17004 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.
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Contrasting diffusion behaviors of O and F atoms on graphene and within bilayer graphene Title : Contrasting diffusion behaviors of O and F atoms on graphene and within bilayer graphene Author : Seho Yi, Jin-Ho Choi, Hyun-Jung Kim, Chul Hong Park, Jun-Hyung Cho Journal : Physical Chemistry Chemical Physics
Contrasting diffusion behaviors of O and F atoms on graphene and within bilayer graphene NUMBER C17003 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.
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Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111) Title : Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111) Author : Xiao-Yan Ren, Hyun-Jung Kim, Seho Yi, Yu Jia, Jun-Hyung Cho Journal : Physical Review B 94, 075436 (2016)
Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111) NUMBER C16001 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.
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Origin of Symmetric Dimer Images of Si (001) Observed in Low-Temperature STM Title : Origin of Symmetric Dimer Images of Si (001) Observed in Low-Temperature STM Author : Xiao-Yan Ren, Hyun-Jung Kim, Chun-Yao Niu, Yu Jia, Jun-Hyung Cho Journal : Sci.Rep. 6, 27868 (2016)
Origin of Symmetric Dimer Images of Si (001) Observed in Low-Temperature STM NUMBER C15020 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.
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Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices Title : Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices Author : Hyun-Jung Kim, Chaokai Li, Ji Feng, Jun-Hyung Cho, Zhenyu Zhang Journal : PHYSICAL REVIEW B 93, 041404(R) (2016)
Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices NUMBER C15019 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.
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Giant spin-orbit-induced spin splitting in Bi zigzag chains on GaAs(110) Title : Giant spin-orbit-induced spin splitting in Bi zigzag chains on GaAs(110) Author : Hyun-Jung Kim, Jun-Hyung Cho Journal : PHYSICAL REVIEW B 92, 085303 (2015)
Giant spin-orbit-induced spin splitting in Bi zigzag chains on GaAs(110) NUMBER C15018 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.
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Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3 Title : Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3 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)
Nature of the Insulating Ground State of the 5d Postperovskite CaIrO3 NUMBER C15017 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.
- Kim, Hyunjin
- Research Fellow
- Protein Folding
- Office : 7321
- Tel : 3878 | Fax : 3820
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- Kim, Min Hyeok
- Research Fellow
- Computational Biophysics
- Office : 7313
- Tel : 3839 | Fax : 3820
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- Kim, Mun Dae
- Project Research Fellow
- Quantum Information
- Office : 8201
- Tel : 2658 | Fax : 3820
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Macroscopic Entangled States in Superconducting Flux Qubits Title : Macroscopic Entangled States in Superconducting Flux Qubits Author : Mun Dae Kim, Sam Young Cho Journal : Journal of Physics: Conference Series
Macroscopic Entangled States in Superconducting Flux Qubits NUMBER P08044 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.
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Coherent Operation of Superconducting Flux Qubits at Optimal Point Title : Coherent Operation of Superconducting Flux Qubits at Optimal Point Author : Mun Dae Kim, Sam Young Cho Journal :
Coherent Operation of Superconducting Flux Qubits at Optimal Point NUMBER P08035 AUTHOR Mun Dae Kim, Sam Young Cho TITLE Coherent Operation of Superconducting Flux Qubits at Optimal Point ARCHIVE FILE 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.
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Superconducting-ferromagnet Junction Phase Qubit Title : Superconducting-ferromagnet Junction Phase Qubit Author : Tae-Wan Noh, Mun Dae Kim, Heung-Sun Sim Journal :
Superconducting-ferromagnet Junction Phase Qubit NUMBER P08010 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.
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Kondo physics in the algebraic spin liquid Title : Kondo physics in the algebraic spin liquid Author : Ki-Seok Kim, Mun Dae Kim Journal : J. Phys.: Condens. Matter 20 (2008) 125206
Kondo physics in the algebraic spin liquid NUMBER P07033 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.
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Spin-gapped incoherent metal with preformed pairing in the doped antiferromagnetic Mott insulator Title : Spin-gapped incoherent metal with preformed pairing in the doped antiferromagnetic Mott insulator Author : Ki-Seok Kim, Mun Dae Kim Journal : Physical Review B 77, 125103 (2008)
Spin-gapped incoherent metal with preformed pairing in the doped antiferromagnetic Mott insulator NUMBER P07032 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.
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Realizable spin models and entanglement dynamics in superconducting flux qubit systems Title : Realizable spin models and entanglement dynamics in superconducting flux qubit systems Author : Qian Qian Shi, Sam Young Cho, Bo Li, Mun Dae Kim Journal : Physical Review B 77, 104511 (2008)
Realizable spin models and entanglement dynamics in superconducting flux qubit systems NUMBER P07028 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.
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Macroscopic Greenberger-Horne-Zeilinger and W States in Flux Qubits Title : Macroscopic Greenberger-Horne-Zeilinger and W States in Flux Qubits Author : Mun Dae Kim, Sam Young Cho Journal : Physical Review B 77, 100508(R) (2008)
Macroscopic Greenberger-Horne-Zeilinger and W States in Flux Qubits NUMBER P07024 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.
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Macroscopic Many-Qubit Interactions in Superconducting Flux Qubits Title : Macroscopic Many-Qubit Interactions in Superconducting Flux Qubits Author : Sam Young Cho, Mun Dae Kim Journal : Physical Review B 77, 212506 (2008)
Macroscopic Many-Qubit Interactions in Superconducting Flux Qubits NUMBER P07023 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.
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Antiferromagnetic metal to heavy-fermion metal quantum phase transition in the Kondo lattice model: A strong-coupling approach Title : Antiferromagnetic metal to heavy-fermion metal quantum phase transition in the Kondo lattice model: A strong-coupling approach Author : Ki-Seok Kim, Mun Dae Kim Journal : Phys. Rev. B vol. 75, 035117 (2007)
Antiferromagnetic metal to heavy-fermion metal quantum phase transition in the Kondo lattice model: A strong-coupling approach NUMBER P07003 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
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Entanglement and Bell States in Superconducting Flux Qubits Title : Entanglement and Bell States in Superconducting Flux Qubits Author : Mun Dae Kim, Sam Young Cho Journal : Physical Review B 75, 134514 (2007)
Entanglement and Bell States in Superconducting Flux Qubits NUMBER P06007 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.
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Controllable Coupling in Phase-Coupled Flux Qubits Title : Controllable Coupling in Phase-Coupled Flux Qubits Author : Mun Dae Kim Journal : PHYSICAL REVIEW B 74 (18): Art. No. 184501 NOV 2006
Controllable Coupling in Phase-Coupled Flux Qubits NUMBER P06006 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.
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Current-phase relation of the SNS junction in a superconducting loop Title : Current-phase relation of the SNS junction in a superconducting loop Author : Mun Dae Kim, Jongbae Hong Journal : EUROPHYSICS LETTERS 73 (1): 90-96 JAN 2006
Current-phase relation of the SNS junction in a superconducting loop NUMBER P05073 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.
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Effect of the Andreev reflection phase shift on the currents of SNS junctions and NS loops Title : Effect of the Andreev reflection phase shift on the currents of SNS junctions and NS loops Author : Mun Dae Kim, Jongbae Hong Journal : J. Korean Phys. Soc. 46, 689 (2005)
Effect of the Andreev reflection phase shift on the currents of SNS junctions and NS loops NUMBER P04056 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.
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Diamagnetic Response of Aharonov-Bohm Rings: Impurity Backward Scatterings Title : Diamagnetic Response of Aharonov-Bohm Rings: Impurity Backward Scatterings Author : Mun Dae Kim, Chul Koo Kim, Kyun Nahm Journal : PHYSICAL REVIEW B 72 (8): Art. No. 085333 AUG 2005
Diamagnetic Response of Aharonov-Bohm Rings: Impurity Backward Scatterings NUMBER P04055 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
- Krah, Alexander
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- Lee, Chang-Woo
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- Lee, Jun-Ho
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Nature of the Insulating Ground State in 5d Postperovskite CaIrO3 Title : Nature of the Insulating Ground State in 5d Postperovskite CaIrO3 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)
Nature of the Insulating Ground State in 5d Postperovskite CaIrO3 NUMBER C15016 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 FILE 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.
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Antiferromagnetic superexchange mediated by a resonant surface state in Sn/Si(111) Title : Antiferromagnetic superexchange mediated by a resonant surface state in Sn/Si(111) Author : Jun-Ho Lee, Xiao-Yan Ren, Yu Jia, Jun-Hyung Cho Journal : Phys. Rev. B 90, 125439 (2014)
Antiferromagnetic superexchange mediated by a resonant surface state in Sn/Si(111) NUMBER C14006 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) ARCHIVE FILE 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.
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- Liu, Lei
- Research Fellow
- Computational Biophysics
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- Mohamed Lazim, Siti Raudah
- Research Fellow
- Protein Folding
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- Nam, Sun-Young
- Research Fellow
- Combinatorics, Representation theory
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- Graph polynomial
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- Park, Jimin
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- Srivastava, Amit
- Research Fellow
- Protein Folding
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