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Oey, Yuzki M.

Publications and source records attributed to Oey, Yuzki M..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Incommensurate charge-stripe correlations in the kagome superconductor CsV 3 Sb 5–x Sn x

The class of AV 3 Sb 5 (A=K, Rb, Cs) kagome metals hosts unconventional charge density wave states seemingly intertwined with their low temperature superconducting phases. The nature of the coupling between these two states and the potential presence of nearby, competing charge instabilities however remain open questions. This phenomenology is strikingly highlighted by the formation of two ‘domes’ in the superconducting transition temperature upon hole-doping CsV 3 Sb 5 . Here we track the evolution of charge correlations upon the suppression of long-range charge density wave order in the first dome and into the second of the hole-doped kagome superconductor CsV 3 Sb 5–x Sn x . Initially, hole-doping drives interlayer charge correlations to become short-ranged with their periodicity diminished along the interlayer direction. Beyond the peak of the first superconducting dome, the parent charge density wave state vanishes and incommensurate, quasi-1D charge correlations are stabilized in its place. These competing, unidirectional charge correlations demonstrate an inherent electronic rotational symmetry breaking in CsV 3 Sb 5 , and reveal a complex landscape of charge correlations within its electronic phase diagram. Our data suggest an inherent 2k ƒ charge instability and competing charge orders in the AV 3 Sb 5 class of kagome superconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Charge order landscape and competition with superconductivity in kagome metals

In the kagome metals AV 3 Sb 5 (A = K, Rb, Cs), three-dimensional charge order is the primary instability that sets the stage for other collective orders to emerge, including unidirectional stripe order, orbital flux order, electronic nematicity and superconductivity. In this report we use high-resolution angle-resolved photoemission spectroscopy to determine the microscopic structure of three-dimensional charge order in AV 3 Sb 5 and its interplay with superconductivity. Our approach is based on identifying an unusual splitting of kagome bands induced by three-dimensional charge order, which provides a sensitive way to refine the spatial charge patterns in neighbouring kagome planes. Here we found a marked dependence of the three-dimensional charge order structure on composition and doping. The observed difference between CsV 3 Sb 5 and the other compounds potentially underpins the double-dome superconductivity in CsV 3 (Sb,Sn) 5 and the suppression of T c in KV 3 Sb 5 and RbV 3 Sb 5 . Our results provide fresh insights into the rich phase diagram of AV 3 Sb 5 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Tuning charge density wave order and superconductivity in the kagome metals KV 3 Sb 5 – x Sn x and RbV 3 Sb 5 – x Sn x

The family of AV 3 Sb 5 (A = K, Rb, Cs) kagome metals exhibits charge density wave (CDW) order, proposed to be chiral, followed by a lower temperature superconducting state. Recent studies have proposed the importance of band structure saddle points proximal to the Fermi energy in governing these two transitions. Here we show the effects of hole doping achieved via chemical substitution of Sn for Sb on the CDW and superconducting states in both KV 3 Sb 5 and RbV 3 Sb 5 and generate a phase diagram. Furthermore, hole doping lifts the Γ pocket and van Hove singularities toward E F causing the superconducting T C in both systems to increase to about 4.5 K, while rapidly suppressing the CDW state.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Fermi level tuning and double-dome superconductivity in the kagome metal CsV 3 Sb 5 – x Sn x

The recently reported AV 3 Sb 5 (A = K , Rb, Cs) family of kagome metals are candidates for unconventional superconductivity and chiral charge density wave (CDW) order; both potentially arise from nested saddle points in their band structures close to the Fermi energy. Here, we use chemical substitution to introduce holes into CsV 3 Sb 5 and unveil an unconventional coupling of the CDW and superconducting states. Specifically, we generate a phase diagram for CsV 3 Sb 5 – x Sn x that illustrates the impact of hole doping the system and lifting the nearest van Hove singularity toward and above E F . Superconductivity exhibits a nonmonotonic evolution with the introduction of holes, resulting in two “domes” peaked at 3.6 and 4.1 K and the rapid suppression of three-dimensional CDW order. Further, the evolution of CDW and superconducting order is compared with the evolution of the electronic band structure of CsV 3 Sb 5 – x Sn x , where the complete suppression of superconductivity seemingly coincides with an electronlike band comprised of Sb p z orbitals pushed above E F .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Structural changes upon magnetic ordering in magnetocaloric AlFe 2 B 2

With a Curie temperature just above room temperature, AlFe 2 B 2 is a useful magnetocaloric material composed of earth-abundant elements. Here, we employ temperature-dependent high-resolution synchrotron X-ray diffraction to establish with high certainty that the paramagnetic to ferromagnetic transition in AlFe 2 B 2 is of second order, showing no discontinuity in lattice parameters or cell volume. Nevertheless, the lattice parameters undergo anisotropic changes across the transition with distinct differences in the thermal expansion coefficients. While the $a$ and $b$ lattice parameters show a positive thermal expansion, $c$ shows a negative thermal expansion. We link these changes to the respective interatomic distances to determine the contribution of magnetism to the anisotropic structural evolution. The work underpins the possible role of magnetostructural coupling in driving the magnetocaloric effect in AlFe 2 B 2 .

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗