A5029309081- Topological Materials and Phenomena
- Advanced Condensed Matter Physics
- Graphene research and applications
- Physics of Superconductivity and Magnetism
- 2D Materials and Applications
- Iron-based superconductors research
- Quantum, superfluid, helium dynamics
- Transition Metal Oxide Nanomaterials
- Electronic and Structural Properties of Oxides
- Inorganic Chemistry and Materials
- Rare-earth and actinide compounds
- Quantum and electron transport phenomena
- Advanced Memory and Neural Computing
- Porphyrin and Phthalocyanine Chemistry
- Surface Chemistry and Catalysis
- Nuclear materials and radiation effects
- Heusler alloys: electronic and magnetic properties
- Quantum many-body systems
- Phase-change materials and chalcogenides
Rice University
2023-2024
University of California, Berkeley
2021
Abstract Charge density waves (CDWs) in kagome metals have been tied to many exotic phenomena. Here, using spectroscopic-imaging scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we study the charge order metal ScV 6 Sn . The similarity of electronic band structures TbV (where ordering is absent) suggests that unlikely be primarily driven by Fermi surface nesting Van Hove singularities. In contrast CDW state cousin metals, find no evidence supporting rotation...
Charge density waves (CDWs) have been tied to a number of unusual phenomena in kagome metals, including rotation symmetry breaking, time-reversal breaking and superconductivity. The majority the experiments thus far focused on CDW states AV3Sb5 FeGe, characterized by 2a0 period. Recently, bulk phase (T* ~ 92 K) with different wave length orientation has reported ScV6Sn6, as first realization state broad RM6X6 structure. Here, using combination scanning tunneling microscopy/spectroscopy...
Magnetism in two-dimensional (2D) materials has attracted considerable attention recently for both fundamental understanding of magnetism and its tunability towards device applications. The isostructural Fe3GeTe2 Fe3GaTe2 are two members the Fe-based van der Waals (vdW) ferromagnet family, but exhibit very different Curie temperatures (TC) 210 360 K, respectively. Here, by using angle-resolved photoemission spectroscopy density functional theory, we systematically compare electronic...
Abstract Non-volatile phase-change memory devices utilize local heating to toggle between crystalline and amorphous states with distinct electrical properties. Expanding on this kind of switching two topologically phases requires controlled non-volatile symmetries. Here, we report the observation reversible stable closely related crystal structures, remarkably electronic in near-room-temperature van der Waals ferromagnet Fe 5− δ GeTe 2 . We show that is enabled by ordering disordering site...
Abstract Kramers nodal lines (KNLs) have recently been proposed theoretically as a special type of Weyl line degeneracy connecting time-reversal invariant momenta. KNLs are robust to spin orbit coupling and inherent all non-centrosymmetric achiral crystal structures, leading unusual spin, magneto-electric, optical properties. However, their existence in real quantum materials has not experimentally established. Here we gather the experimental evidence pointing at presence SmAlSi, metal that...
Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing the momentum-resolved single-particle spectral function of materials. Historically, in situ magnetic fields have been carefully avoided as they are detrimental to control photoelectron trajectory during detection process. However, field an important experimental knob both and tuning symmetry-breaking phases electronic topology quantum In this paper, we introduce easily implementable method realizing tunable at...
The two-dimensional material ${\mathrm{Cr}}_{2}{\mathrm{Ge}}_{2}{\mathrm{Te}}_{6}$ is a member of the class insulating van der Waals (vdW) magnets. Here, using high resolution angle-resolved photoemission spectroscopy in detailed temperature dependence study, we identify clear response electronic structure to dimensional crossover form two distinct scales marking onsets modifications structure. Specifically, observe Te $p$-orbital-dominated bands undergo changes at Curie transition ${T}_{C}$...
The incorporation of nonhexagonal rings into graphene nanoribbons (GNRs) is an effective strategy for engineering localized electronic states, bandgaps, and magnetic properties. Here, we demonstrate the successful synthesis having four-membered ring (cyclobutadienoid) linkages by using on-surface approach involving direct contact transfer coronene-type precursors followed thermally assisted [2 + 2] cycloaddition. resulting coronene-cyclobutadienoid feature a narrow 600-meV bandgap novel...
In the iron-based superconductors, unconventional superconductivity emerges in proximity to intertwined electronic orders consisting of an nematic order and a spin density wave (SDW). Recently, ${\mathrm{BaNi}}_{2}{\mathrm{As}}_{2}$, like its well-known analog ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$, has been discovered host symmetry-breaking structural transition but coupled unidirectional charge (CDW) instead SDW, providing novel platform study orders. Here, through systematic...
In the quest for novel quantum states driven by topology and correlation, kagome lattice materials have garnered significant interest due to their distinctive electronic band structures, featuring flat bands (FBs) arising from destructive interference of wave function. The tuning FBs chemical potential would lead possibility liberating instabilities that emergent orders. Despite extensive studies, direct evidence tuned participation in orders been lacking bulk materials. Here using a...
Magnetism in two-dimensional (2D) materials has attracted considerable attention recently for both fundamental understanding of magnetism and their tunability towards device applications. The isostructural Fe$_3$GeTe$_2$ Fe$_3$GaTe$_2$ are two members the Fe-based van der Waals (vdW) ferromagnet family, but exhibit very different Curie temperatures (T$_C$) 210 K 360 K, respectively. Here, by using angle-resolved photoemission spectroscopy density functional theory, we systematically compare...
Emergent phases often appear when the electronic kinetic energy is comparable to Coulomb interactions. One approach seek material systems as hosts of such emergent realize localization wavefunctions due geometric frustration inherent in crystal structure, resulting flat bands. Recently, efforts have found a wide range exotic two-dimensional kagome lattice, including magnetic order, time-reversal symmetry breaking charge nematicity, and superconductivity. However, interlayer coupling layers...
The ability to reversibly toggle between two distinct states in a non-volatile method is important for information storage applications. Such devices have been realized phase-change materials, which utilizes local heating methods crystalline and an amorphous state with electrical properties. To expand such kind of switching topologically phases requires symmetries. Here we report the observation reversible stable closely-related crystal structures remarkably electronic near room temperature...
Magnetic kagome materials provide a fascinating playground for exploring the interplay of magnetism, correlation and topology. Many magnetic systems have been reported including binary FemXn (X = Sn, Ge; m:n 3:1, 3:2, 1:1) family rare earth RMn6Sn6 (R earth) family, where their flat bands are calculated to be near Fermi level in paramagnetic phase. While partially filling band is predicted give rise Stoner-type ferromagnetism, experimental visualization splitting across ordering temperature...
Topological insulators are materials that have an insulating bulk interior while maintaining gapless boundary states against back scattering. Bi
Magnetic kagome materials provide a fascinating playground for exploring the interplay of magnetism, correlation and topology. Many magnetic systems have been reported including binary FemXn (X=Sn, Ge; m:n = 3:1, 3:2, 1:1) family rare earth RMn6Sn6 (R earth) family, where their flat bands are calculated to be near Fermi level in paramagnetic phase. While partially filling band is predicted give rise Stoner-type ferromagnetism, experimental visualization splitting across ordering temperature...
Topological insulators are materials with an insulating bulk interior while maintaining gapless boundary states against back scattering. Bi$_2$Se$_3$ is a prototypical topological insulator Dirac-cone surface state around $\Gamma$. Here, we present controlled methodology to gradually remove Se atoms from the Se-Bi-Se-Bi-Se quintuple layers, eventually forming bilayer-Bi on top of bulk. Our method allows us track and confirm its robustness throughout modification. Importantly, report...
Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for probing the momentum-resolved single-particle spectral function of materials. Historically, $\textit{in situ}$ magnetic fields have been carefully avoided as they are detrimental to control photoelectron trajectory during detection process. However, field an important experimental knob both and tuning symmetry-breaking phases electronic topology in quantum In this paper, we introduce easily implementable method...
The two-dimensional (2D) material Cr$_2$Ge$_2$Te$_6$ is a member of the class insulating van der Waals magnets. Here, using high resolution angle-resolved photoemission spectroscopy in detailed temperature dependence study, we identify clear response electronic structure to dimensional crossover form two distinct scales marking onsets modifications structure. Specifically, observe Te $p$-orbital-dominated bands undergo changes at Curie transition T$_C$ while Cr $d$-orbital-dominated begin...