SOOHYEON SHIN - Academia.edu (original) (raw)
Papers by SOOHYEON SHIN
Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendou... more Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendous attention due to their unique properties and intricate interplay with exotic correlated phenomena, topological and symmetry-breaking states. However, the origin of the CDW order remains a topic of debate. The discovery of ScV6Sn6, a vanadium-based bilayer kagome metal exhibiting an in-plane √3 x√3 R30° CDW order with time-reversal symmetry breaking, provides a novel platform to explore the underlying mechanism behind the unconventional CDW. Here, we combine high-resolution angle-resolved photoemission spectroscopy, Raman scattering measurements and density functional theory to investigate the electronic structures and phonon modes of ScV6Sn6 and their evolution with temperature. We identify topologically nontrivial Dirac surface states and multiple van Hove singularities (VHSs) in the vicinity of the Fermi level, with one VHS near the ꝁ point exhibiting nesting wave vectors in proximit...
The origin of unconventional superconductivity and its relationship to a T=0 K continuous quantum... more The origin of unconventional superconductivity and its relationship to a T=0 K continuous quantum phase transition (a quantum critical point, QCP), which is hidden inside the dome of a superconducting state, have long been an outstanding puzzle in correlated superconductors. The observation and tuning of the hidden QCP, which is critical in resolving the mystery, however, has been rarely reported due to lack of ideal systems. The helical antiferromagnet CrAs provides an example in which a dome of superconductivity appears at a pressure where its magnetic transition goes to zero temperature. Here we report the tuning of a projected critical point in CrAs via Al chemical doping (Al-CrAs) and separation of the magnetic critical point from the pressure-induced superconducting phase. When CrAs is doped with Al, its AFM ordering temperature TN increases from 260 K to 270 K. With applied pressure, TN decreases and extrapolates to zero Kelvin near 4.5 kbar, which is shifted from 8 kbar for ...
Bulletin of the American Physical Society, 2019
Pressure-induced superconductivity in the helical magnet CrAs occurs in close proximity to a T = ... more Pressure-induced superconductivity in the helical magnet CrAs occurs in close proximity to a T = 0 K antiferromagnetic (AFM) transition, indicating a possible interplay between the two broken symmetries. When CrAs is doped with Al (Al-CrAs), its AFM ordering temperature TN increases from 260 K to 270 K. With applied pressure, TN decreases and extrapolates to zero Kelvin near 4.5 kbar, which is shifted from the projected critical pressure of 9 kbar of undoped CrAs. Evidence for an AFM quantum-critical point (QCP) near 4.5 kbar in Al-CrAs includes a funnel of anomalously enhanced electron scattering emerging at low temperatures from the critical pressure and a non-Fermi liquid resistivity. Pressure-induced superconductivity, in contrast, is almost independent of Al doping and forms a dome with essentially the identical maximum Tc and same optimal pressure of 9 kbar as in pure CrAs. The clear separation between the AFM QCP and Tc maximum in Al-CrAs suggests that the attractive Cooper-p...
Journal of Applied Physics, 2017
We report the upper critical field (Hc2) and its anisotropy in the pressure-induced superconducto... more We report the upper critical field (Hc2) and its anisotropy in the pressure-induced superconductor CrAs. At ambient pressure, CrAs shows an antiferromagnetic phase transition at TN ∼ 264 K, where magnetostriction occurs simultaneously. TN is rapidly suppressed with increasing pressure and bulk superconductivity is induced near 7 kbar, above which the signature associated with TN is not visible in electrical resistivity measurements. With further increasing pressure, the superconducting phase shows a broad dome shape centered at the optimal pressure of 12.2 kbar. The Hc2 anisotropy of CrAs at 12.2 kbar, γHc2 = H//a/H⊥a, increases with decreasing temperature and becomes saturated at lower temperatures. Taken together with the positive curvature in Hc2 near Tc, these results suggest that the pressure-induced superconductor CrAs possesses multiple superconducting gaps.
We report the synthesis of Ni-doped BaFe2Se3 single crystals by using a flux method. X-ray diffra... more We report the synthesis of Ni-doped BaFe2Se3 single crystals by using a flux method. X-ray diffraction (XRD) of Ba(Fe1xNix)2Se3 shows a gradual peak shift with an increase in the nominal Ni-doping rate, x = 0, 0.05, and 0.10, due to a decrease in unit-cell volume. All samples show a spin glass transition, and temperature dependence of magnetic susceptibility shows a negligible change in the spin-glass transition temperature (Tg) with Ni concentration x. The temperature dependence of electrical resistivity for BaFe2Se3 shows an insulating behavior, and the resistivity value at 295 K and the activation energy (Ea) obtained from the Arrhenius plot decrease with increasing x. These results suggest that the Ni doping can be effectively worked as a dopant for electron charge carriers, but is less efficient in controlling the magnetic property, such as spin glass transition, in the
Physical Review B
Kondo metal CePtAl 4 Ge 2 exhibits long-range antiferromagnetic order below 2.3 K. Neutron powder... more Kondo metal CePtAl 4 Ge 2 exhibits long-range antiferromagnetic order below 2.3 K. Neutron powderdiffraction experiments reveal that Ce moments order antiferromagnetically with an incommensurate ordering wave vector k = (1.39, 0, 0.09). Inelastic neutron powder scattering experiments show a magnetic excitation at 14.5 meV, which corresponds to the first excited state due to the crystalline electric field splitting of the ground-state multiplet of Ce 3+. The temperature and field dependence of the magnetization of CePtAl 4 Ge 2 is consistent with a doublet ground state with a dominant | j z = 1/2 character and a first excited doublet | j z = 3/2 at 14.5 meV.
Physical Review B
Because the iron-ladder compounds BaFe 2 X 3 (X = S or Se) possess highly anisotropic crystal, el... more Because the iron-ladder compounds BaFe 2 X 3 (X = S or Se) possess highly anisotropic crystal, electronic, and magnetic structures, the order in certain degrees of freedom leads to interesting interplays among them. Here we present a systematic study of the dielectric behavior of BaFe 2 S 3 and BaFe 2 Se 3 along all crystallographic directions revealing the conduction mechanism and its relation to the underlying magnetic ordering. The temperature dependence of the DC conductivity indicates that the antiferromagnetic order is accompanied by a transition in the conduction mechanism from a simple activated behavior above T N to three-dimensional variable range hopping below T N. Although the magnetic structures that develop on BaFe 2 S 3 and BaFe 2 Se 3 are rather different-despite nearly identical crystal structures-we do not find significant difference in the conduction mechanism.
Physical Review Materials
We report the dependence of antiferromagnetism on Zn-doping concentration in the newly synthesize... more We report the dependence of antiferromagnetism on Zn-doping concentration in the newly synthesized CeRh(In 1-x Zn x) 5 single crystal with x 0.023. X-ray-diffraction measurements showed a smooth decrease of lattice parameters with an increasing Zn concentration, indicating a positive chemical pressure effect. The electrical resistivity, specific heat, and magnetic susceptibility measurements revealed that the antiferromagnetic transition temperature T N initially decreases from 3.8 K for pure CeRhIn 5 to 3.1 K at x = 0.012; then, it becomes flat, remaining at approximately 3.1 K between Zn concentrations of 0.012 and 0.017, and finally, it increases to 3.3 K at 0.023 Zn concentration. These results suggest that the change in the electronic structure induced by Zn doping is more important than the chemical pressure effects with regard to tuning the magnetic order. A study on the electronic structure and pressure tuning of the newly synthesized heavy-fermion compound CeRh(In 1-x Zn x) 5 , which does not include a toxic element, is expected to further enhance our understanding of the competing ground states emerging in heavy-fermion systems.
![Research paper thumbnail of Corrigendum to “Synthesis and characterization of the heavy-fermion compound CePtAl4Ge2” [J. Alloys Compd. 738 (2018) 550–555]](https://attachments.academia-assets.com/71519603/thumbnails/1.jpg)
](Journal of Alloys and Compounds
npj Quantum Materials
The origin of unconventional superconductivity and its relationship to a T = 0 K quantum critical... more The origin of unconventional superconductivity and its relationship to a T = 0 K quantum critical point (QCP), which is hidden inside the dome of a superconducting state, have long been an outstanding puzzle in strongly correlated superconductors. The observation and tuning of the hidden QCP, which is key to resolving the mystery, however, has been rarely reported. Here we report the controlling of a hidden QCP in the helical antiferromagnet CrAs and separation of the tuned QCP from the pressureinduced superconducting phase. The Al doping in CrAs increases the antiferromagnetic ordering temperature T N from 265 to 275 K, while it suppresses the QCP from 8 to 4.5 kbar. Pressure-induced superconductivity in the high-pressure regime is almost independent of Al doping, but superconductivity below 6 kbar is suppressed, revealing the clear separation between the tuned antiferromagnetic QCP and T c maximum. These discoveries illustrate subtleties in the interplay between superconductivity and quantum criticality and warrant a deeper insight in understanding of unconventional superconductivity.
NPG Asia Materials
Inhomogeneous superconductivity in rare-earth (RE)-doped CaFe 2 As 2 (Ca122) compounds leads to a... more Inhomogeneous superconductivity in rare-earth (RE)-doped CaFe 2 As 2 (Ca122) compounds leads to a novel state of matter in which the superconducting and magnetic states can be simultaneously controlled by using an electric current (I). Both La-and Ce-doped Ca122 single crystals show a very broad superconducting transition width (ΔT c) due to their non-bulk nature. Surprisingly, ΔT c becomes sharper or broader after an electric current larger than a threshold value (I t) is applied, with a concomitant change in the normal-state magnetism. The sharpened (broadened) ΔT c is accompanied by a decrease (an increase) in the amplitude of the ferromagnetic signals. The sensitive changes in the superconductivity and magnetism that occur when an external current is applied are related to the inhomogeneous electronic states that originate from the Fe magnetic state and/or self-organized superconducting/magnetic composites in Ca122 compounds. These discoveries shed new light on the role of Fe in Fe-based superconductors and will provide new ideas for the design of novel superconducting devices.
Journal of the Korean Physical Society
Journal of Alloys and Compounds
Nanoscale, Jan 16, 2018
Transition metal oxide thin films show versatile electric, magnetic, and thermal properties which... more Transition metal oxide thin films show versatile electric, magnetic, and thermal properties which can be tailored by deliberately introducing macroscopic grain boundaries via polycrystalline solids. In this study, we focus on the modification of magnetic and thermal transport properties by fabricating single- and polycrystalline epitaxial SrRuOthin films using pulsed laser epitaxy. Using the epitaxial stabilization technique with an atomically flat polycrystalline SrTiOsubstrate, an epitaxial polycrystalline SrRuOthin film with the crystalline quality of each grain comparable to that of its single-crystalline counterpart is realized. In particular, alleviated compressive strain near the grain boundaries due to coalescence is evidenced structurally, which induced the enhancement of ferromagnetic ordering of the polycrystalline epitaxial thin film. The structural variations associated with the grain boundaries further reduce the thermal conductivity without deteriorating the electroni...
Superconductor Science and Technology
We investigate the effects of magnetic impurities on the upper critical field (μ0Hc2) in La-doped... more We investigate the effects of magnetic impurities on the upper critical field (μ0Hc2) in La-doped CaFe2As2 (LaCa122) single crystals. The magnetic field dependency of the superconducting transition temperature (Tc) for LaCa122 is rapidly suppressed at low fields up to ~1 kOe despite its large μ0Hc2(0) value on the order of tens of Tesla, resulting in a large positive curvature of μ0Hc2(T) near Tc. The magnetization hysteresis (M − H) loop at temperatures above Tc shows a ferromagnetic signal and the M(H) value rapidly increases with increasing magnetic field up to ~1 kOe. Taken together with the linear suppression of Tc with the magnetization in the normal state, these results suggest that the large upward curvature of μ0Hc2(T) near Tc in La-doped CaFe2As2 mainly originates from the suppression of superconductivity due to the presence of magnetic impurities.
Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendou... more Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendous attention due to their unique properties and intricate interplay with exotic correlated phenomena, topological and symmetry-breaking states. However, the origin of the CDW order remains a topic of debate. The discovery of ScV6Sn6, a vanadium-based bilayer kagome metal exhibiting an in-plane √3 x√3 R30° CDW order with time-reversal symmetry breaking, provides a novel platform to explore the underlying mechanism behind the unconventional CDW. Here, we combine high-resolution angle-resolved photoemission spectroscopy, Raman scattering measurements and density functional theory to investigate the electronic structures and phonon modes of ScV6Sn6 and their evolution with temperature. We identify topologically nontrivial Dirac surface states and multiple van Hove singularities (VHSs) in the vicinity of the Fermi level, with one VHS near the ꝁ point exhibiting nesting wave vectors in proximit...
The origin of unconventional superconductivity and its relationship to a T=0 K continuous quantum... more The origin of unconventional superconductivity and its relationship to a T=0 K continuous quantum phase transition (a quantum critical point, QCP), which is hidden inside the dome of a superconducting state, have long been an outstanding puzzle in correlated superconductors. The observation and tuning of the hidden QCP, which is critical in resolving the mystery, however, has been rarely reported due to lack of ideal systems. The helical antiferromagnet CrAs provides an example in which a dome of superconductivity appears at a pressure where its magnetic transition goes to zero temperature. Here we report the tuning of a projected critical point in CrAs via Al chemical doping (Al-CrAs) and separation of the magnetic critical point from the pressure-induced superconducting phase. When CrAs is doped with Al, its AFM ordering temperature TN increases from 260 K to 270 K. With applied pressure, TN decreases and extrapolates to zero Kelvin near 4.5 kbar, which is shifted from 8 kbar for ...
Bulletin of the American Physical Society, 2019
Pressure-induced superconductivity in the helical magnet CrAs occurs in close proximity to a T = ... more Pressure-induced superconductivity in the helical magnet CrAs occurs in close proximity to a T = 0 K antiferromagnetic (AFM) transition, indicating a possible interplay between the two broken symmetries. When CrAs is doped with Al (Al-CrAs), its AFM ordering temperature TN increases from 260 K to 270 K. With applied pressure, TN decreases and extrapolates to zero Kelvin near 4.5 kbar, which is shifted from the projected critical pressure of 9 kbar of undoped CrAs. Evidence for an AFM quantum-critical point (QCP) near 4.5 kbar in Al-CrAs includes a funnel of anomalously enhanced electron scattering emerging at low temperatures from the critical pressure and a non-Fermi liquid resistivity. Pressure-induced superconductivity, in contrast, is almost independent of Al doping and forms a dome with essentially the identical maximum Tc and same optimal pressure of 9 kbar as in pure CrAs. The clear separation between the AFM QCP and Tc maximum in Al-CrAs suggests that the attractive Cooper-p...
Journal of Applied Physics, 2017
We report the upper critical field (Hc2) and its anisotropy in the pressure-induced superconducto... more We report the upper critical field (Hc2) and its anisotropy in the pressure-induced superconductor CrAs. At ambient pressure, CrAs shows an antiferromagnetic phase transition at TN ∼ 264 K, where magnetostriction occurs simultaneously. TN is rapidly suppressed with increasing pressure and bulk superconductivity is induced near 7 kbar, above which the signature associated with TN is not visible in electrical resistivity measurements. With further increasing pressure, the superconducting phase shows a broad dome shape centered at the optimal pressure of 12.2 kbar. The Hc2 anisotropy of CrAs at 12.2 kbar, γHc2 = H//a/H⊥a, increases with decreasing temperature and becomes saturated at lower temperatures. Taken together with the positive curvature in Hc2 near Tc, these results suggest that the pressure-induced superconductor CrAs possesses multiple superconducting gaps.
We report the synthesis of Ni-doped BaFe2Se3 single crystals by using a flux method. X-ray diffra... more We report the synthesis of Ni-doped BaFe2Se3 single crystals by using a flux method. X-ray diffraction (XRD) of Ba(Fe1xNix)2Se3 shows a gradual peak shift with an increase in the nominal Ni-doping rate, x = 0, 0.05, and 0.10, due to a decrease in unit-cell volume. All samples show a spin glass transition, and temperature dependence of magnetic susceptibility shows a negligible change in the spin-glass transition temperature (Tg) with Ni concentration x. The temperature dependence of electrical resistivity for BaFe2Se3 shows an insulating behavior, and the resistivity value at 295 K and the activation energy (Ea) obtained from the Arrhenius plot decrease with increasing x. These results suggest that the Ni doping can be effectively worked as a dopant for electron charge carriers, but is less efficient in controlling the magnetic property, such as spin glass transition, in the
Physical Review B
Kondo metal CePtAl 4 Ge 2 exhibits long-range antiferromagnetic order below 2.3 K. Neutron powder... more Kondo metal CePtAl 4 Ge 2 exhibits long-range antiferromagnetic order below 2.3 K. Neutron powderdiffraction experiments reveal that Ce moments order antiferromagnetically with an incommensurate ordering wave vector k = (1.39, 0, 0.09). Inelastic neutron powder scattering experiments show a magnetic excitation at 14.5 meV, which corresponds to the first excited state due to the crystalline electric field splitting of the ground-state multiplet of Ce 3+. The temperature and field dependence of the magnetization of CePtAl 4 Ge 2 is consistent with a doublet ground state with a dominant | j z = 1/2 character and a first excited doublet | j z = 3/2 at 14.5 meV.
Physical Review B
Because the iron-ladder compounds BaFe 2 X 3 (X = S or Se) possess highly anisotropic crystal, el... more Because the iron-ladder compounds BaFe 2 X 3 (X = S or Se) possess highly anisotropic crystal, electronic, and magnetic structures, the order in certain degrees of freedom leads to interesting interplays among them. Here we present a systematic study of the dielectric behavior of BaFe 2 S 3 and BaFe 2 Se 3 along all crystallographic directions revealing the conduction mechanism and its relation to the underlying magnetic ordering. The temperature dependence of the DC conductivity indicates that the antiferromagnetic order is accompanied by a transition in the conduction mechanism from a simple activated behavior above T N to three-dimensional variable range hopping below T N. Although the magnetic structures that develop on BaFe 2 S 3 and BaFe 2 Se 3 are rather different-despite nearly identical crystal structures-we do not find significant difference in the conduction mechanism.
Physical Review Materials
We report the dependence of antiferromagnetism on Zn-doping concentration in the newly synthesize... more We report the dependence of antiferromagnetism on Zn-doping concentration in the newly synthesized CeRh(In 1-x Zn x) 5 single crystal with x 0.023. X-ray-diffraction measurements showed a smooth decrease of lattice parameters with an increasing Zn concentration, indicating a positive chemical pressure effect. The electrical resistivity, specific heat, and magnetic susceptibility measurements revealed that the antiferromagnetic transition temperature T N initially decreases from 3.8 K for pure CeRhIn 5 to 3.1 K at x = 0.012; then, it becomes flat, remaining at approximately 3.1 K between Zn concentrations of 0.012 and 0.017, and finally, it increases to 3.3 K at 0.023 Zn concentration. These results suggest that the change in the electronic structure induced by Zn doping is more important than the chemical pressure effects with regard to tuning the magnetic order. A study on the electronic structure and pressure tuning of the newly synthesized heavy-fermion compound CeRh(In 1-x Zn x) 5 , which does not include a toxic element, is expected to further enhance our understanding of the competing ground states emerging in heavy-fermion systems.
Journal of Alloys and Compounds
npj Quantum Materials
The origin of unconventional superconductivity and its relationship to a T = 0 K quantum critical... more The origin of unconventional superconductivity and its relationship to a T = 0 K quantum critical point (QCP), which is hidden inside the dome of a superconducting state, have long been an outstanding puzzle in strongly correlated superconductors. The observation and tuning of the hidden QCP, which is key to resolving the mystery, however, has been rarely reported. Here we report the controlling of a hidden QCP in the helical antiferromagnet CrAs and separation of the tuned QCP from the pressureinduced superconducting phase. The Al doping in CrAs increases the antiferromagnetic ordering temperature T N from 265 to 275 K, while it suppresses the QCP from 8 to 4.5 kbar. Pressure-induced superconductivity in the high-pressure regime is almost independent of Al doping, but superconductivity below 6 kbar is suppressed, revealing the clear separation between the tuned antiferromagnetic QCP and T c maximum. These discoveries illustrate subtleties in the interplay between superconductivity and quantum criticality and warrant a deeper insight in understanding of unconventional superconductivity.
NPG Asia Materials
Inhomogeneous superconductivity in rare-earth (RE)-doped CaFe 2 As 2 (Ca122) compounds leads to a... more Inhomogeneous superconductivity in rare-earth (RE)-doped CaFe 2 As 2 (Ca122) compounds leads to a novel state of matter in which the superconducting and magnetic states can be simultaneously controlled by using an electric current (I). Both La-and Ce-doped Ca122 single crystals show a very broad superconducting transition width (ΔT c) due to their non-bulk nature. Surprisingly, ΔT c becomes sharper or broader after an electric current larger than a threshold value (I t) is applied, with a concomitant change in the normal-state magnetism. The sharpened (broadened) ΔT c is accompanied by a decrease (an increase) in the amplitude of the ferromagnetic signals. The sensitive changes in the superconductivity and magnetism that occur when an external current is applied are related to the inhomogeneous electronic states that originate from the Fe magnetic state and/or self-organized superconducting/magnetic composites in Ca122 compounds. These discoveries shed new light on the role of Fe in Fe-based superconductors and will provide new ideas for the design of novel superconducting devices.
Journal of the Korean Physical Society
Journal of Alloys and Compounds
Nanoscale, Jan 16, 2018
Transition metal oxide thin films show versatile electric, magnetic, and thermal properties which... more Transition metal oxide thin films show versatile electric, magnetic, and thermal properties which can be tailored by deliberately introducing macroscopic grain boundaries via polycrystalline solids. In this study, we focus on the modification of magnetic and thermal transport properties by fabricating single- and polycrystalline epitaxial SrRuOthin films using pulsed laser epitaxy. Using the epitaxial stabilization technique with an atomically flat polycrystalline SrTiOsubstrate, an epitaxial polycrystalline SrRuOthin film with the crystalline quality of each grain comparable to that of its single-crystalline counterpart is realized. In particular, alleviated compressive strain near the grain boundaries due to coalescence is evidenced structurally, which induced the enhancement of ferromagnetic ordering of the polycrystalline epitaxial thin film. The structural variations associated with the grain boundaries further reduce the thermal conductivity without deteriorating the electroni...
Superconductor Science and Technology
We investigate the effects of magnetic impurities on the upper critical field (μ0Hc2) in La-doped... more We investigate the effects of magnetic impurities on the upper critical field (μ0Hc2) in La-doped CaFe2As2 (LaCa122) single crystals. The magnetic field dependency of the superconducting transition temperature (Tc) for LaCa122 is rapidly suppressed at low fields up to ~1 kOe despite its large μ0Hc2(0) value on the order of tens of Tesla, resulting in a large positive curvature of μ0Hc2(T) near Tc. The magnetization hysteresis (M − H) loop at temperatures above Tc shows a ferromagnetic signal and the M(H) value rapidly increases with increasing magnetic field up to ~1 kOe. Taken together with the linear suppression of Tc with the magnetization in the normal state, these results suggest that the large upward curvature of μ0Hc2(T) near Tc in La-doped CaFe2As2 mainly originates from the suppression of superconductivity due to the presence of magnetic impurities.