Abstract(Quasi-)one-dimensional systems exhibit various fascinating properties such as Luttinger liquid behavior, Peierls transition, novel topological phases, and the accommodation of unique quasiparticles (e.g., spinon, holon, and soliton, etc.). Here we study molybdenum blue bronze A0.3MoO3 (A = K, Rb), a canonical quasi-one-dimensional charge-density-wave material, using laser-based angle-resolved photoemission spectroscopy. Our experiment suggests that the normal phase of A0.3MoO3 is a prototypical Luttinger liquid, from which the charge-density-wave emerges with decreasing temperature. Prominently, we observe strong renormalizations of band dispersions, which are recognized as the spectral function of Holstein polaron derived from band-selective electron-phonon coupling in the system. We argue that the strong electron-phonon coupling plays an important role in electronic properties and the charge-density-wave transition in blue bronzes. Our results not only reconcile the long-standing heavy debates on the electronic properties of blue bronzes but also provide a rare platform to study interesting excitations in Luttinger liquid materials.
Ultrathin films of intrinsic magnetic topological insulator
MnBi2Te4 exhibit fascinating quantum properties
such
as the quantum anomalous Hall effect and the axion insulator state.
In this work, we systematically investigate the evolution of the electronic
structure of MnBi2Te4 thin films. With increasing
film thickness, the electronic structure changes from an insulator
type with a large energy gap to one with in-gap topological surface
states, which is, however, still in drastic contrast to the bulk material.
By surface doping of alkali-metal atoms, a Rashba split band gradually
emerges and hybridizes with topological surface states, which not
only reconciles the puzzling difference between the electronic structures
of the bulk and thin-film MnBi2Te4 but also
provides an interesting platform to establish Rashba ferromagnet that
is attractive for (quantum) anomalous Hall effect. Our results provide
important insights into the understanding and engineering of the intriguing
quantum properties of MnBi2Te4 thin films.
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