Bypassing the Structural Bottleneck in the Ultrafast Melting of Electronic Order

Abstract

Impulsive optical excitation generally results in a complex nonequilibrium electron and lattice dynamics that involves multiple processes on distinct timescales, and a common conception is that for times shorter than about 100 fs the gap in the electronic spectrum is not seriously affected by lattice vibrations. Here, however, by directly monitoring the photoinduced collapse of the spectral gap in a canonical chargedensity-wave material, the blue bronze Rb 0.3 MoO 3 , we find that ultrafast (∼60 fs) vibrational disordering due to efficient hot-electron energy dissipation quenches the gap significantly faster than the typical structural bottleneck time corresponding to one half-cycle oscillation (∼315 fs) of the coherent chargedensity-wave amplitude mode. This result not only demonstrates the importance of incoherent lattice motion in the photoinduced quenching of electronic order, but also resolves the perennial debate about the nature of the spectral gap in a coupled electron-lattice system.

Band-selective Holstein polaron in Luttinger liquid material A0.3MoO3 (A = K, Rb)

“…Data in panels b and c were collected using 7 eV laser, whereas the data in panels e and f were collected using He lamp (Supplementary Figure 7). energy of the B band near E F strongly depends on the temperature (Supplementary Note 8), further confirming the strong EPC in blue bronzes 22,34,36,37 . Likewise, the estimated coherence length of the Holstein polaron is in good comparison with the CDW period of ~9 Å, and the phonon mode involved in the Holstein polaron is intimately related to the CDW transition 33,44,45 , suggesting that the strong EPC and its bandselectivity may play an important role in the electronic properties and the LL-to-CDW transition in blue bronzes.…”

“…Interestingly, we observe strong renormalizations of the band dispersions, which are identified as the spectral function of Holstein polaron derived from band-selective EPC in the system. We conclude that the strong EPC 22,34,36,37 , in addition to the FS nesting 25,26 , has an important role in electronic properties and the LL-to-CDW transition in blue bronzes. Our results not only help understand the long-standing mysteries in blue bronzes, including the non-Fermi liquid behavior, the pseudogap above T CDW , and the mechanism of the CDW transition but also provide a rare platform to study the intriguing EPC in LL materials, which will also shed light on the understanding of rich physics in other Q1D materials.…”

“…Nevertheless, the absence of the Fermi edge in the density of states 27,28 has challenged this scenario and sparked heavy debates about non-Fermi liquid behavior [29][30][31] and (pseudo)gap above T CDW in the system 25,27,32,33 . Moreover, the underlying microscopic interaction that is crucial for the CDW transition is also under heavy debate 25,26,33,34 . These controversial results call for a comprehensive understanding of the single-particle spectral properties of the system.…”

Observation of dimension-crossover of a tunable 1D Dirac fermion in topological semimetal NbSixTe2

“…Despite these great interests, the experimental realization of a tunable 1D electronic states appears to be rare. Physical systems with 1D electron systems include the self-assembly growth of metal wires on semiconductor surface (e.g., In 41 , Ge 42,43 , Si 44 , GaN 45 wires on Si(111), Au wires on Ge(110) 46 and Ge(001) 47 ), MoO x 48,49 , Li 0.9 Mo 6 O 17 50 , Rb 0.3 MoO 3 51 , TaSe 3 52 , XTe 3 (X = Nb, V, Ti) 53 , NbSe 3 54 , etc. However, a few of them can be served as a stoichiometric compounds system for research on tunable 1D electronic states [55][56][57] .…”

Optical amplification in a CDW-phase of a quasi-two dimensional material

“…[64,65] In this context a lot of current research around the optical excitation and melting of CDW phases was done. [66][67][68][69][70][71][72] Furthermore, spin-selective excitations, [73] strain effects on CDWs [74] and also T iT e 2 /T iSe 2 Moire Bilayer [48] were investigated and T iSe 2 was suggested as a saturable absorber. [75] Also, research in initialization methods, [76,77] first attempts to describe pump/probe experiments [78] or the collective excitations of an exciton insulator in a cavity [79] was published.…”