Time-periodic light field can dress the electronic states and lead to light-induced emergent properties in quantum materials. While below-gap pumping is regarded favorable for Floquet engineering, so far direct experimental evidence of momentum-resolved band renormalization still remains missing. Here, we report black phosphorus by at photon energy 160 meV, which below gap, distinction between near-resonance revealed. Our Letter demonstrates engineering upon pumping, provides insights...

Intense light-field can dress both Bloch electrons inside crystals and photo-emitted free in the vacuum, dubbed as Floquet Volkov states respectively. These quantum further interfere coherently, modulating dressed states. Here, we report experimental evidence of Floquet-Volkov interference a semiconductor - black phosphorus. A highly asymmetric modulation spectral weight is observed for states, such asymmetry be controlled by rotating pump polarization. Our work reveals between different...

Twisted bilayer graphene with a twist angle of exactly 30° (30°-TBG) is unique two-dimensional (2D) van der Waals (vdW) system because its quasicrystalline nature. Here we report, for the first time, scanning tunneling microscopy (STM) measurements 30°-TBG that was obtained in controllable way by using transfer-assisted fabrication pair sheets. The order 30°-TBG, showing 12-fold rotational symmetry, directly visualized atomic-resolved STM images. In presence high magnetic fields, observed...

MnBi8Te13 is an intrinsic ferromagnetic (FM) topological insulator with different complex surface terminations. Resolving the electronic structures of termination surfaces and manipulation state are important. Here, by using micrometer spot time- angle-resolved photoemission spectroscopy (μ-TrARPES), we resolve reveal ultrafast dynamics upon photoexcitation. Photoinduced filling hybridization gap observed for Bi2Te3 quintuple layer directly above MnBi2Te4 accompanied a nontrivial shift...

Time- and angle-resolved photoemission spectroscopy (TrARPES) is a powerful technique for capturing the ultrafast dynamics of charge carriers revealing photo-induced phase transitions in quantum materials. However, lack widely tunable probe photon energy, which critical accessing dispersions at different out-of-plane momentum kz TrARPES measurements, has hindered investigation 3D materials, such as Dirac or Weyl semimetals. Here, we report development system with highly energy from 5.3 to...

Revealing the ultrafast dynamics of three-dimensional (3D) Dirac fermions is critical for both fundamental science and device applications. So far, how cooling 3D differs from that two-dimensional (2D) whether there population inversion are questions to be answered. Here we reveal in a model semimetal Cd3As2 by time- angle-resolved photoemission spectroscopy with tunable probe photon energy. The energy- momentum-resolved relaxation rate shows linear dependence on energy, suggesting fermion...

Revealing the fine electronic structure is critical for understanding underlying physics of low-dimensional materials. Angle-resolved photoemission spectroscopy (ARPES) a powerful experimental technique mapping out structure. By reducing photon energy (e.g. to 6 eV) using laser sources, greatly improved momentum resolution can be achieved, thereby providing opportunities ``zooming in'' and even revealing previously unresolvable bands near Brillouin zone center. Here, by quasi-one-dimensional...

Topological Dirac nodal-line semimetals host topologically nontrivial electronic structure with crossings around the Fermi level, which could affect photocarrier dynamics and lead to novel relaxation mechanisms. Herein, by using time- angle-resolved photoemission spectroscopy, we reveal previously-inaccessible linear dispersions of bulk conduction bands above level in a semimetal PtSn$_4$, as well momentum temporal evolution gapless nodal lines. A surprisingly ultrafast within few hundred...

Distinguishing and controlling the extent of Mottness is important for materials where energy scales on-site Coulomb repulsion $U$ bandwidth $W$ are comparable. Here, we report ultrafast electronic dynamics $1T\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ by time- angle-resolved photoemission spectroscopy. A comparison electron intermediate phase (I-phase) as well low-temperature commensurate charge density wave (C-CDW) shows distinctive dynamics. While I-phase characterized an instantaneous...

Van der Waals superlattices are important for tailoring the electronic structures and properties of layered materials. Here we report superconducting structure a natural van superlattice (PbSe)$_{1.14}$NbSe$_2$. Anisotropic superconductivity with transition temperature $T_c$ = 5.6 $\pm$ 0.1 K, which is higher than monolayer NbSe$_2$, revealed by transport measurements on high-quality samples. Angle-resolved photoemission spectroscopy (ARPES) reveal two-dimensional charge transfer 0.43...

Symmetry breaking plays an important role in the fields of physics, ranging from particle physics to condensed matter physics. In solid-state materials, phase transitions are deeply linked underlying symmetry breakings, resulting a rich variety emergent phases. Such breakings often induced by controlling chemical composition and temperature or applying electric field, strain, etc. this work, we demonstrate ultrafast glide-mirror black phosphorus through Floquet engineering. Upon...

Strong light-matter interaction provides opportunities for tailoring the physical properties of quantum materials on ultrafast timescale by forming photon-dressed electronic states, i.e., Floquet-Bloch states. While light field can in principle imprint its symmetry onto so far, how to experimentally detect and further engineer states remains elusive. Here utilizing time- angle-resolved photoemission spectroscopy (TrARPES) with polarization-dependent study, we directly visualize parity black...

Abstract The weak van der Waals interaction between adjacent layers of quasi-two-dimensional materials provides opportunities for inserting intercalants to induce novel properties distinct from the host materials. Here we report induced superconductivity in an intercalated SnSe 2 crystal by using a new type intercalants—organic cations ionic liquids, [C MIm] + and [DEMB] . intercalation both increases interlayer spacing leads with T c 7.1 6.9 K large superconducting anisotropy....

Developing a widely tunable vacuum ultraviolet (VUV) source with sub-100 fs pulse duration is critical for ultrafast pump-probe techniques such as time- and angle-resolved photoemission spectroscopy (TrARPES). While probe photon energy of 5.3-7.0 eV has been recently implemented TrARPES by using KBe2BO3F2 (KBBF) device, the time resolution 280-320 still not ideal, which mainly limited VUV generated KBBF device. Here, designing new specially optimized applications, an optimum 55 obtained...

Abstract Manipulating the strength of interlayer coupling is an effective strategy to induce intriguing properties in layered materials. Recently, enhanced superconductivity has been reported Weyl semimetal MoTe 2 and WTe via ionic liquid (IL) cation intercalation. However, how enhancement depends on interaction still remains elusive. Here by inserting IL cations with different sizes into through this strategy, we are able tune spacing intercalated samples reveal dependence superconducting...

High-quality ultrafast light sources are critical for developing advanced time- and angle-resolved photoemission spectroscopy (TrARPES). While the application of high harmonic generation (HHG) in TrARPES has increased substantially over past decade, optimization HHG probe beam size selective control polarization, which important measurements, have been rarely explored. In this work, we report implementation high-quality source with an optimum down to 57 μm × 90 polarization control, together...

Abstract Capturing the ultrafast dynamics over a large momentum space is critical for revealing relationship between electronic and structural modulation in quantum materials. Here, by performing time- angle-resolved photoemission spectroscopy measurements at Synergetic Extreme Condition User Faclity (SECUF) equipped with extreme ultraviolet light source, we reveal of charge density wave (CDW) material 1T-TiSe 2 upon photo-excitation. The pump-induced CDW melting revealed from two aspects,...

Abstract Revealing the ultrafast carrier dynamics with spatial, energy and time resolution is critical for achieving a comprehensive understanding of electronic two-dimensional (2D) materials heterostructures. Here, by time-resolved photoemission electron microscopy (Tr-PEEM) measurements, we reveal layer-dependent monolayer (1 ML), bilayer (2 4 ML graphene as well bulk graphite. In contrast to 2 thicker graphene, photo-excited electrons in 1 relax much faster, which attributed unique...

Optical metasurfaces are one of the most studied objects in field electromagnetism. However, designing optical to meet desired transfer function is still very challenging. Genetic Algorithm (GA) an optimization algorithm that simulates process inheritance and evolution organisms their natural environment. It's able perform crossover, mutation, other operations on many these gene fragments ultimately obtain optimal genetic outcome. In this paper, structural parameters optimized by matrix...

Van der Waals superlattices are important for tailoring the electronic structures and properties of layered materials. Here we report superconducting structure a natural van superlattice (PbSe)$_{1.14}$NbSe$_2$. Anisotropic superconductivity with transition temperature $T_c$ = 5.6 $\pm$ 0.1 K, which is higher than monolayer NbSe$_2$, revealed by transport measurements on high-quality samples. Angle-resolved photoemission spectroscopy (ARPES) reveal two-dimensional charge transfer 0.43...

Distinguishing and controlling the extent of Mottness is important for materials where energy scales onsite Coulomb repulsion U bandwidth W are comparable. Here we report ultrafast electronic dynamics 1T-TaS$_2$ by time- angle-resolved photoemission spectroscopy. A comparison electron newly-discovered intermediate phase (I-phase) as well low-temperature commensurate charge density wave (C-CDW) shows distinctive dynamics. While I-phase characterized an instantaneous response nearly...