Exposing a Hidden State Shining intense laser light on material can temporarily alter its properties. The effect usually subsides after few picoseconds, unless the system is trapped in metastable state, which case transient period may last as long microseconds. Stojchevska et al. (p. 177 ) observed that, following exposure to 35-femtosecond pulse, layered dichalcogenide 1T -TaS 2 entered stable “hidden” state not present equilibrium phase diagram and stayed there indefinitely. switch hidden...

Abstract The functionality of computer memory elements is currently based on multi-stability, driven either by locally manipulating the density electrons in transistors or switching magnetic ferroelectric order. Another possibility between metallic and insulating phases motion ions, but their speed limited slow nucleation inhomogeneous percolative growth. Here we demonstrate fast resistance a charge wave system caused pulsed current injection. As pulse travels through material, it converts...

We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors. show that primary process is electron-phonon interaction and extract a measure its strength, second moment Eliashberg function λ[ω2] = 800 ± 200 meV2 La(1.85)Sr(0.15)CuO4 400 100 YBa(2)Cu(3)O(6.5). These values suggest possible fundamental role in superconducting pairing mechanism.

Revealing the relaxation mechanisms of hidden states in transition metal dichalcogenides leads to control metastability.

We use ultrashort intense laser pulses to study superconducting state vaporization dynamics in La2-xSrxCuO4 (x=0.1 and 0.15) on the femtosecond time scale. find that energy density required vaporize is 2.0+/-0.8 2.6+/-1.0 K/Cu for x=0.1 0.15, respectively. This significantly greater than condensation density, indicating quasiparticles share a large amount of with boson glue bath this Considering detail both spin lattice relaxation pathways which take place relevant scale approximately...

The 2D semiconductor MoS 2 in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show strong photovoltaic effect work active material high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy sub‐ps ms time scales used study photoexcitation dynamics . results suggest that...

The coupling of phonons with collective modes and single-particle gap excitations associated one- (1d) two-directional (2d) electronically driven charge-density wave (CDW) ordering in metallic $R{\mathrm{Te}}_{3}$ is investigated as a function rare-earth ion chemical pressure ($R=\mathrm{Tb},\mathrm{Dy},\mathrm{Ho}$) using femtosecond pump-probe spectroscopy. From the $T$ dependence CDW ${\ensuremath{\Delta}}_{\mathrm{CDW}}$ amplitude mode, we find that while transition to 1d-CDW ordered...

We use femtosecond spectroscopy to investigate the quasiparticle relaxation and low-energy electronic structure in a nearly optimally doped pnictide superconductor with T{c}=49.5 K. Multiple processes are evident, distinct superconducting state recombination dynamics exhibiting T-dependent gap, clear "pseudogaplike" feature an onset above 180 K indicating existence of temperature-independent gap magnitude Delta{PG}=61+/-9 meV T{c}. Both pseudogap components show saturation as function...

The processes leading to nonthermal condensate vaporization and charge-density wave (CDW) melting with femtosecond laser pulses is systematically investigated in different materials. We find that relatively slow (tau_v ~ 1 ps) inefficient superconductors, exhibiting a strong systematic dependence of the energy Uv on Tc. In contrast, CDW order proceeds rapidly (tau_m = 50 200 fs) more efficiently. A quantitative model describing observed behavior superconductors proposed based phonon-mediated...

Metastable self-organized electronic states in quantum materials are of fundamental importance, displaying emergent dynamical properties that may be used new generations sensors and memory devices. Such typically formed through phase transitions under non-equilibrium conditions the final state is reached processes span a large range timescales. Conventionally, diagrams thought as static, without temporal evolution. However, many functional arise result complex changes material occurring on...

We investigate the quasiparticle (QP) relaxation and low-energy electronic structure in undoped SmFeAsO near-optimally doped ${\text{SmFeAsO}}_{0.8}{\text{F}}_{0.2}$ single crystals--exhibiting spin-density wave (SDW) ordering superconductivity, respectively--using pump-probe femtosecond spectroscopy. In crystals a process is observed, showing remarkable critical slowing down of QP dynamics at SDW transition temperature ${T}_{\text{SDW}}\ensuremath{\simeq}125\text{ }\text{K}$....

We investigate the quasiparticle relaxation and low-energy electronic structure in undoped SrFe_2As_2 exhibiting spin-density wave (SDW) ordering using optical pump-probe femtosecond spectroscopy. A remarkable critical slowing down of dynamics at SDW transition temperature T_SDW = 200K is observed. From dependence transient reflectivity amplitude we determine SDW-state charge gap magnitude, 2Delta_SDW/k_BT_SDW=7.2+-1. The second moment Eliashberg function, lambda<(hbar...

We systematically investigate the photoexcited (PE) quasiparticle (QP) relaxation and low-energy electronic structure in electron doped Ba(Fe${}_{1\ensuremath{-}x}$Co${}_{x}$)${}_{2}$As${}_{2}$ single crystals as a function of Co doping, $0\ensuremath{\le}x\ensuremath{\le}0.11$. The evolution photoinduced reflectivity transients with $x$ proceeds no abrupt changes. In orthorhombic spin-density-wave (SDW) state, bottleneck associated partial charge-gap opening is detected, similar to previous...

The dynamics of excitations with different symmetry is investigated in the superconducting (SC) and normal state high-temperature superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi2212) using optical pump-probe (Pp) experiments light polarizations at doping levels. observation distinct selection rules for SC excitations, present A$_{{\rm 1g}}$ B$_{{\rm symmetries, PG 2g}}$ by probe absence any dependence on pump beam polarization leads to unequivocal conclusion existence a...

We study the incoherent recombination of topological defects created during a rapid quench charge-density-wave system through electronic ordering transition. Using specially devised three-pulse femtosecond optical spectroscopy technique we follow evolution order parameter over wide range time scales. By careful consideration thermal processes can clearly identify intrinsic defect annihilation on scale $\ensuremath{\sim}30\text{ }\text{ }\mathrm{ps}$ and find possible signature extrinsic...

The properties of a system charged particles on 2D lattice, subject to an anisotropic Jahn-Teller-type interaction and 3D Coulomb repulsion, are investigated. In the mean-field approximation without interaction, displays phase transition first order. When long-range is included, Monte Carlo simulations show that very diverse mesoscopic textures, ranging from spatially disordered pairs ordered arrays stripes, or clusters, depending only ratio two interactions (and particle density)....

We investigate the relaxation dynamics of photoexcited quasiparticles (QPs) in underdoped Bi${}_{2}$Sr${}_{2}$CaCu${}_{2}$O${}_{8+\ensuremath{\delta}}$ (${T}_{\mathrm{c}}=78$ K). By changing excitation energy and polarization probe beam, two different types dynamics, associated with superconducting (SC) pseudogap (PG) QPs, are quantitatively analyzed independently. From temperature dependencies, we obtained SC gap, ${\ensuremath{\Delta}}_{\text{SC}}(0)=24$ meV, using BCS-type...

The transition to a hidden metastable state in 1T-TaS2 is investigated real time using coherent time-resolved femtosecond spectroscopy. Relying on spectral differences between phonon modes the equilibrium states and state, temperature-tuning lifetime, we perform stroboscopic measurements of electronic response switching oscillation frequency through transition. Very fast collective mode observed (400 fs), comparable timescale (300 fs). A slower, 4.7 ps process attributed lattice relaxation....

Controllable switching to and from metastable states of matter using electromagnetic fields could potentially revolutionize electronic logic memory devices. Here, we investigate the effect two-dimensional strain on between a photoinduced "hidden" state stable charge-ordered in ultrathin 1T-TaS2 crystal films different substrates, photoexcited by 35 fs laser pulses. The differential contraction sample substrate shows very large negative coefficient hidden transition, implying that stability...

A 'pseudogap' was introduced by Mott to describe a state of matter that has minimum in the density states at Fermi level, deep enough for become localized. It can arise either from Coulomb repulsion between electrons, and/or incipient charge or spin order. Here we employ ultrafast spectroscopy study dynamical properties normal pseudogap transition prototype high-temperature superconductor Bi2Sr2CaCu2O8+δ. We perform systematic temperature and doping dependence photodestruction recovery...

In classical superconductors an energy gap and phase coherence appear simultaneously with pairing at the transition to superconducting state. high-temperature superconductors, possibility that are distinct independent processes has led intense experimental search of their separate manifestations, but so far without success. Using femtosecond spectroscopy methods we now show it is possible clearly fluctuation dynamics amplitude from relaxation above critical temperature. Empirically...

Comparison of photoinduced local modes (PILM's) insulating ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.3}$ and ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Gd}}_{\mathit{x}}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8}$ with Raman spectra their metallic counterparts suggests that carrier injection anomalously increases the frequencies phonons involving z-axis apex-oxygen motion in both dilute (insulator) concentrated (metallic)...

Analysis of the $a\ensuremath{-}b$ plane optical conductivity ${\ensuremath{\sigma}}_{\mathrm{ab}}$ for both twinned and untwinned ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ as a function temperature doping shows that below well-defined ${T}^{*},$ dip in spectrum systematically appears separating infrared charge excitation into two components with distinct energy scales. The change from monotonic behavior is found to be concurrent onset phonon...