Alessandra Lanzara's research while affiliated with University of California, Berkeley and other places
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Publications (335)
Screening, a ubiquitous phenomenon associated with the shielding of electric fields by surrounding charges, has been widely adopted as a means to modify a material’s properties. While most studies have relied on static changes of screening through doping or gating thus far, here we demonstrate that screening can also drive the onset of distinct qua...
Near the magic angle, strong correlations drive many intriguing phases in twisted bilayer graphene (tBG) including unconventional superconductivity and chern insulation. Whether correlations can tune symmetry breaking phases in tBG at intermediate (≳ 2°) twist angles remains an open fundamental question. Here, using ARPES, we study the effects of m...
In kagome metal CsV3Sb5, multiple intertwined orders are accompanied by both electronic and structural instabilities. These exotic orders have attracted much recent attention, but their origins remain elusive. The newly discovered CsTi3Bi5 is a Ti-based kagome metal to parallel CsV3Sb5. Here, we report angle-resolved photoemission experiments and f...
The density of states at the Fermi surface controls many material properties by influencing the low-energy interactions of conductive electrons. Typically, external tuning knobs generate only small perturbations to the density of states in crystals, since their band structure depends strongly on the lattice potential. In contrast, quantum well stat...
α-RuCl3 is considered to be the top candidate material for the experimental realization of the celebrated Kitaev model, where ground states are quantum spin liquids with interesting fractionalized excitations. It is, however, known that additional interactions beyond the Kitaev model trigger in α-RuCl3 a long-range zigzag antiferromagnetic ground s...
Molecular crystals are a flexible platform to induce novel electronic phases. Due to the weak forces between molecules, intermolecular distances can be varied over larger ranges than interatomic distances in atomic crystals. On the other hand, the hopping terms are generally small, which results in narrow bands, strong correlations, and heavy elect...
Molecular crystals are a flexible platform to induce novel electronic phases. Due to the weak forces between molecules, intermolecular distances can be varied over relatively larger ranges than interatomic distances in atomic crystals. On the other hand, the hopping terms are generally small, which results in narrow bands, strong correlations and h...
Scientific data acquisition is a problem domain that has been underserved by its computational tools despite the need to efficiently use hardware, to guarantee validity of the recorded data, and to rapidly test ideas by configuring experiments quickly and inexpensively. High-dimensional physical spectroscopies, such as angle-resolved photoemission...
In our understanding of solids, the formation of highly spatially coherent electronic states, fundamental to command the quantum behavior of materials, relies on the existence of discrete translational symmetry of the crystalline lattice. In contrast, in the absence of long-range order, as in the case of non-crystalline materials, the electronic st...
The exciton, a bound state of an electron and a hole, is a fundamental quasiparticle induced by coherent light–matter interactions in semiconductors. When the electrons and holes are in distinct spatial locations, spatially indirect excitons are formed with a much longer lifetime and a higher condensation temperature. One of the ultimate frontiers...
Long viewed as passive elements, antiferromagnetic materials have emerged as promising candidates for spintronic devices due to their insensitivity to external fields and potential for high-speed switching. Recent work exploiting spin and orbital effects has identified ways to electrically control and probe the spins in metallic antiferromagnets, e...
Crystalline symmetries have played a central role in the identification and understanding of quantum materials. Here we investigate whether an amorphous analogue of a well known three-dimensional strong topological insulator has topological properties in the solid state. We show that amorphous Bi2Se3 thin films host a number of two-dimensional surf...
Electron-hole asymmetry is a fundamental property in solids that can determine the nature of quantum phase transitions and the regime of operation for devices. The observation of electron-hole asymmetry in graphene and recently in twisted graphene and moiré heterostructures has spurred interest into whether it stems from single-particle effects or...
Long viewed as passive elements, antiferromagnetic materials have emerged as promising candidates for spintronic devices due to their insensitivity to external fields and potential for high-speed switching. Recent work exploiting spin and orbital effects has identified ways to electrically control and probe the spins in metallic antiferromagnets, e...
Van der Waals ferromagnets are thrilling materials from both a fundamental and technological point of view. VI 3 is an interesting example, with a complex magnetism that differentiates it from the first reported Cr based layered ferromagnets. Here, we show in an indirect way through angle resolved photoemission spectroscopy experiments, the importa...
![(a) Comparison of the dynamics of Se4p\documentclass[12pt]{minimal}...](publication/363798926/figure/fig4/AS:11431281085957703@1663988614141/a-Comparison-of-the-dynamics-of-Se4pdocumentclass12ptminimal-usepackageamsmath_Q320.jpg)
The formation of a charge density wave state is characterized by an order parameter. The way it is established provides unique information on both the role that correlation plays in driving the charge density wave formation and the mechanism behind its formation. Here we use time and angle resolved photoelectron spectroscopy to optically perturb th...
The formation of a charge density wave state is characterized by an order parameter. The way it is established provides unique information on both the role that correlation plays in driving the charge density wave formation and the mechanism behind its formation. Here we use time and angle resolved photoelectron spectroscopy to optically perturb th...
Charge density waves (CDW) are states of broken symmetry with a periodic modulation of charge and lattice typically leading to the opening of a gap in the band structure. In the model CDW system 1T-TiSe2 such a gap opens up between its Se4p valence and Ti3d conduction band, accompanied by a change of dispersion. These changes are crucial in underst...
Optical excitation serves as a powerful approach to control the electronic structure of layered van der Waals materials via many-body screening effects, induced by photoexcited free carriers, or via light-driven coherence, such as optical Stark and Bloch-Siegert effects. Although theoretical work has also pointed to an exotic mechanism of renormali...
The future of modern optoelectronics and spintronic devices relies on our ability to control the spin and charge degrees of freedom at ultrafast timescales. Rashba spin-split quantum well states, 2D states that develop at the surface of strong spin-orbit coupling materials, are ideal given the tunability of their energy and spin states. So far, how...
Layered ferromagnets are thrilling materials from both a fundamental and technological point of view. VI3 is an interesting example, with a complex magnetism that differentiates it from the first reported Cr based layered ferromagnets. Here, we show in an indirect way through Angle Resolved Photoemission Spectroscopy (ARPES) experiments, the import...
Optical excitation serves as a powerful approach to control the electronic structure of layered Van der Waals materials via many-body screening effects, induced by photoexcited free carriers, or via light-driven coherence, such as optical Stark and Bloch-Siegert effects. Although theoretical work has also pointed to an exotic mechanism of renormali...
Charge density waves (CDW) are states of broken symmetry with a periodic modulation of charge and lattice typically leading to the opening of a gap in the band structure. In the model CDW system 1T-TiSe$_2$ such a gap opens up between its Se$_{4p}$ valence and Ti$_{3d}$ conduction band, accompanied by a change of dispersion. These changes are cruci...
The formations of charge and lattice orders are generally coupled in charge density wave (CDW) materials and share identical order wave vectors. Although this situation is usually satisfied in a large class of two-dimensional materials, it falls short in describing the so-called CDW-like phase transition in layered tantalum ditelluride (TaTe2), acc...
A flat band structure in momentum space is considered key for the realization of novel phenomena. A topological flat band, also known as a drumhead state, is an ideal platform to drive new exotic topological quantum phases. Using angle-resolved photoemission spectroscopy experiments, we reveal the emergence of a highly localized surface state in a...
Spin-orbit coupling emerging out of a material's global inversion symmetry breaking has been long known to act as a pair breaking mechanism to the superconducting order parameter. However, when spin-orbit coupling emerges from local inversion symmetry breaking, an unexpected coexistence with superconductivity might occur. Although lattice driven lo...
We report an ultrafast increase of the quasi-particle bandgap and effective mass in photoexcited monolayer MoS 2 on HOPG, utilizing extreme-ultraviolet time- and angle-resolved photoemission spectroscopy (XUV-trARPES). Combined with theoretical models, we attribute these compelling band renormalizations to the excitonic effects from bound electron-...
By using extreme-ultraviolet time- and angle-resolved photoemission spectroscopy (XUV-trARPES), we visualized the photoemission signature and ultrafast inter-state transitions for the electron-hole plasma and exciton states in monolayer MoS 2 with full visions of energy and momentum.
A gentle reconstruction
Changes in the volume of a material’s Fermi surface are typically associated with the breaking of symmetry. Maksimovic et al . found evidence for an unusual type of this Fermi surface reconstruction, one without symmetry breaking, in the heavy fermion compound cerium cobalt indium (CeCoIn 5 ). Doping the material with tin le...
A topological flatband, also known as drumhead states, is an ideal platform to drive new exotic topological quantum phases. Using angle-resolved photoemission spectroscopy experiments, we reveal the emergence of a highly localized possible drumhead surface state in a topological semimetal BaAl4 and provide its full energy and momentum space topolog...
The search for materials with flat electronic bands continues due to their potential to drive strong correlation and symmetry breaking orders. Electronic moirés formed in van der Waals heterostructures have proved to be an ideal platform. However, there is no holistic experimental picture for how superlattices modify electronic structure. By combin...
The discovery of Weyl semimetals (WSMs) has fueled tremendous interest in condensed matter physics. The realization of WSMs requires the breaking of either inversion symmetry (IS) or time-reversal symmetry (TRS). WSMs can be categorized into type-I and type-II WSMs, which are characterized by untilted and strongly tilted Weyl cones, respectively. T...
Spin-orbit (SO) coupling combined with space inversion symmetry breaking is at the origin of the lifting of the spin degeneracy in the band structure of many materials. The momentum-dependent energy splitting and the degree of spin polarization are indicative of the strength and symmetry of the SO interaction, and enter in the figure of merit of es...
Electron-hole asymmetry is a fundamental property in solids that can determine the nature of quantum phase transitions and the regime of operation for devices. The observation of electron-hole asymmetry in graphene and recently in the phase diagram of bilayer graphene has spurred interest into whether it stems from disorder or from fundamental inte...
The BaAl4 prototype crystal structure is the most populous of all structure types, and is the building block for a diverse set of sub-structures including the famous ThCr2Si2 family that hosts high-temperature superconductivity and numerous magnetic and strongly correlated electron systems. The MA4 family of materials (M = Sr, Ba, Eu; A = Al, Ga, I...
The BaAl$_4$ prototype crystal structure is the most populous of all structure types, and is the building block for a diverse set of sub-structures including the famous ThCr$_2$Si$_2$ family that hosts high-temperature superconductivity and numerous magnetic and strongly correlated electron systems. The MA$_4$ family of materials (M=Sr, Ba, Eu; A=A...
In the past decade, the advent of time-resolved spectroscopic tools has provided a new ground to explore fundamental interactions in solids and to disentangle degrees of freedom whose coupling leads to broad structures in the frequency domain. Time- and angle-resolved photoemission spectroscopy (tr-ARPES) has been utilized to directly study the rel...
Spin orbit assisted Mott insulators such as sodium iridate (Na2IrO3) have been an important subject of study in recent years. In these materials, the interplay of electronic correlations, spin-orbit coupling, crystal field effects, and a honeycomb arrangement of ions bring exciting ground states, predicted in the frame of the Kitaev model. The insu...
Nematicity, where rotational symmetry is broken while translational symmetry is conserved, is prevalent in high-temperature superconductors. In particular, nematic quantum critical point has been universally found near the optimum doping of the superconducting dome of several iron-based superconductor families. In such a regime, evidence for strong...
The appearance of topologically protected spin-momentum locked surface states in topological insulators gives rise to robust room temperature spin currents making them ideal candidates for the realization of spintronic devices. New methods are needed to access and manipulate such currents with timescales that are compatible with modern electronics....
Spin orbit assisted Mott insulators such as sodium iridate (Na$_2$IrO$_3$) have been an important subject of study in the recent years. In these materials, the interplay of electronic correlations, spin-orbit coupling, crystal field effects and a honeycomb arrangement of ions bring exciting ground states, predicted in the frame of the Kitaev model....
The advent of higher resolution and throughput photoemission spectroscopy experiments has made angle-resolved photoemission spectroscopy (ARPES) a critical tool for the study of quantum materials. The simultaneous development of novel ARPES techniques, including nano/μ-ARPES, spin-resolved ARPES, and pump-probe ARPES mirrors the expansion in scanni...
The emergence of saddle-point Van Hove singularities (VHSs) in the density of states, accompanied by a change in Fermi surface topology, Lifshitz transition, constitutes an ideal ground for the emergence of different electronic phenomena, such as superconductivity, pseudo-gap, magnetism, and density waves. However, in most materials the Fermi level...
Crystalline symmetries have played a central role in the identification of topological materials. The use of symmetry indicators and band representations have enabled a classification scheme for crystalline topological materials, leading to large scale topological materials discovery. In this work we address whether amorphous topological materials,...
Recent direct experimental observation of multiple highly dispersive C60 valence bands has allowed for a detailed analysis of the unusual photoemission traits of these features through photon energy- and polarization-dependent measurements. Previously obscured dispersions and strong photoemission traits are now revealed by specific light polarizati...
In the past decade, the advent of time-resolved spectroscopic tools has provided a new ground to explore fundamental interactions in solids and to disentangle degrees of freedom whose coupling leads to broad structures in the frequency domain. Time- and angle-resolved photoemission spectroscopy (tr-ARPES) has been utilized to directly study the rel...
Recent direct experimental observation of multiple highly-dispersive C$_{60}$ valence bands has allowed for a detailed analysis of the unique photoemission traits of these features through photon energy- and polarization-dependent measurements. Previously obscured dispersions and strong photoemission traits are now revealed by specific light polari...
Time- and angle-resolved photoelectron spectroscopy (trARPES) is a powerful method to track the ultrafast dynamics of quasiparticles and electronic bands in energy and momentum space. We present a setup for trARPES with 22.3 eV extreme-ultraviolet (XUV) femtosecond pulses at 50-kHz repetition rate, which enables fast data acquisition and access to...
While long-theorized, the direct observation of multiple highly dispersive C60 valence bands has eluded researchers for more than two decades due to a variety of intrinsic and extrinsic factors. Here we report a realization of multiple highly dispersive (330–520 meV) valence bands in pure thin film C60 on a novel substrate—the three-dimensional top...
We study how time- and angle-resolved photoemission (tr-ARPES) reveals the dynamics of BCS-type, s-wave superconducting systems with time-varying order parameters. Approximate methods are discussed, based on previous approaches to either optical conductivity or quantum dot transport, to enable computationally efficient prediction of photoemission s...
Revealing spin-orbit coupling in a cuprate
Strong coupling between the spin and orbital degrees of freedom is crucial in generating the exotic band structure of topological insulators. The combination of spin-orbit coupling with electronic correlations could lead to exotic effects; however, these two types of interactions are rarely found to be str...
Time- and angle-resolved photoelectron spectroscopy (trARPES) is a powerful method to track the ultrafast dynamics of quasiparticles and electronic bands in energy and momentum space. We present a setup for trARPES with 22.3 eV extreme-ultraviolet (XUV) femtosecond pulses at 50-kHz repetition rate, which enables fast data acquisition and access to...
We study how time- and angle-resolved photoemission (tr-ARPES) reveals the dynamics of BCS-type, s-wave superconducting systems with time-varying order parameters. Approximate methods are discussed, based on previous approaches to either optical conductivity or quantum dot transport, in order to enable computationally efficient prediction of photoe...
Understanding the fine interplay between spin and orbital degrees of freedom in the surface states of topological insulators is the key to the development of next-generation spintronics devices. So far, the majority of studies have focused on the helical spin texture of the topologically protected surface state (TSS) and little attention has been d...
The interaction between a magnetic impurity, such as cerium (Ce) atom, and surrounding electrons has been one of the core problems in understanding many-body interaction in solid and its relation to magnetism. Kondo effect, the formation of a new resonant ground state with quenched magnetic moment, provides a general framework to describe many-body...
Because of the important role of electron-boson interactions in conventional superconductivity, it has long been asked whether any similar mechanism is at play in high-temperature cuprate superconductors. Evidence for strong electron-boson coupling is observed in cuprates with angle-resolved photoemission spectroscopy (ARPES), in the form of a disp...
We have measured the signatures of electronic energy scales and their doping evolution in the band structure of (Sr1−xLax)3Ir2O7 using angle-resolved photoemission spectroscopy. While band splittings and positions corresponding to the bilayer splitting and spin-orbit coupling undergo only small changes, the Mott gap and effective mass of both the l...
DOI:https://doi.org/10.1103/PhysRevB.96.199902
Direct experimental investigations of the low-energy electronic structure of the Na$_2$IrO$_3$ iridate insulator are sparse and draw two conflicting pictures. One relies on flat bands and a clear gap, the other involves dispersive states approaching the Fermi level, pointing to surface metallicity. Here, by a combination of angle-resolved photoemis...
Direct experimental investigations of the low-energy electronic structure of the Na2IrO3 iridate insulator are sparse and draw two conflicting pictures. One relies on flat bands and a clear gap, the other involves dispersive states approaching the Fermi level, pointing to surface metallicity. Here, by a combination of angle-resolved photoemission,...
The electron band structure of graphene on SrTiO3 substrate has been investigated as a function of temperature. The high-resolution angle-resolved photoemission study reveals that the spectral width at Fermi energy and the Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a BN substrate. Near the charge neutrality, the ene...
The interaction between graphene and substrates provides a viable route to enhance the functionality of both materials. Depending on the nature of electronic interaction at the interface, the electron band structure of graphene is strongly influenced, allowing us to make use of the intrinsic properties of graphene or to design additional functional...
We report on an orbital and temperature dependent study of the onset of coherent quasiparticles in V<sub>2</sub>O<sub>3</sub> single crystal. By using polarized infrared spectroscopy we demonstrate that the electronic coherence temperature is strongly orbital dependent, being about 400 K for e<sub>g</sub><sup>π</sup> orbitals and 500 K for the a<su...
Strong spin-orbit coupling creates exotic electronic states such as Rashba and topological surface states, which hold promise for technologies involving the manipulation of spin. Only recently has the complexity of these surface states been appreciated: they are composed of several atomic orbitals with distinct spin textures in momentum space. A co...
The perovskite iridates Sr2IrO4 and Sr3Ir2O7 represent novel systems for exploring the electronic structure that is characteristic of Mott insulators upon carrier doping. Using angle-resolved photoemission spectroscopy (ARPES), we reveal a previously unobserved suppression of spectral weight near the Fermi level in the conduction band of very light...
Charge transfer at the interface between dissimilar materials is at the heart of electronics and photovoltaics. Here we study the molecular orientation, electronic structure, and local charge transfer at the interface region of C60 deposited on graphene, with and without supporting substrates such as hexagonal boron nitride. We employ ab initio den...
One of the most puzzling features of high-temperature cuprate superconductors is the pseudogap state, which appears above the temperature at which superconductivity is destroyed. There remain fundamental questions regarding its nature and its relation to superconductivity. But to address these questions, we must first determine whether the pseudoga...
The intriguing electronic properties of two-dimensional materials motivates experiments to resolve their rapid, microscopic interactions and dynamics across momentum space. Essential insight into the electronic momentum-space dynamics can be obtained directly via time- and angle-resolved photoemission spectroscopy (trARPES). We discuss the developm...
Using angle resolved photoemission spectroscopy, we report the first band dispersions and distinct features of the bulk Fermi surface (FS) in the paramagnetic metallic phase of the prototypical metal-insulator transition material V2O3. Along the c axis we observe both an electron pocket and a triangular holelike FS topology, showing that both V 3d...
Supplementary Figures 1-6
Topological insulators host spin-polarized surface states born out of the energetic inversion of bulk bands driven by the spin-orbit interaction. Here we discover previously unidentified consequences of band-inversion on the surface electronic structure of the topological insulator Bi$_2$Se$_3$. By performing simultaneous spin, time, and angle-reso...
Techniques in time- and angle-resolved photoemission spectroscopy have facilitated a number of recent advances in the study of quantum materials. We review developments in this field related to the study of incoherent nonequilibrium electron dynamics, the analysis of interactions between electrons and collective excitations, the exploration of dres...
The concept of stimulated emission of bosons has played an important role in modern science and technology, and constitutes the working principle for lasers. In a stimulated emission process, an incoming photon enhances the probability that an excited atomic state will transition to a lower energy state and generate a second photon of the same ener...
We develop a computationally inexpensive model to examine the dynamics of boson-assisted electron relaxation in solids, studying nonequilibrium dynamics in a metal, in a nodal superconductor with a stationary density of states, and in a nodal superconductor where the gap dynamically opens. In the metallic system, the electron population resembles a...
The ability to probe symmetry breaking transitions on their natural timescales is one of the grand challenges in non-equilibirum physics. Stripe ordering represents an intriguing type of broken symmetry, where complex interactions result in atomic-scale lines of charge and spin density. While phonon anomalies and periodic distortions attest the imp...
The interaction between two different materials can present novel phenomena that are quite different from the physical properties observed when each material stands alone. Strong electronic correlations, such as magnetism and superconductivity, can be produced as the result of enhanced Coulomb interactions between electrons. Two-dimensional materia...
The condensation of an electron superfluid from a conventional metallic state
at a critical temperature $T_c$ is described well by the BCS theory. In the
underdoped copper-oxides, high-temperature superconductivity condenses instead
from a nonconventional metallic "pseudogap" phase that exhibits a variety of
non-Fermi liquid properties. Recently, i...
The 2015 User Meeting brought together 405 ALS users from around the world, many of whom shared insights and sparked discussion with presentations of their ALS research highlights. UEC Chair Chris Cappa launched the meeting with a welcome, followed by another from Berkeley Lab Director Paul Alivisatos. Speaking of the vitality and community that's...
We demonstrate a novel table-top trARPES setup that combines a bright 50-kHz source of narrowband, extreme ultraviolet (XUV) pulses at 22.3 eV with UHV photoemission instrumentation, enabling sensitive access to dynamics over a large momentum space.
Recent progress in the field of topological states of matter has largely been initiated by the discovery of bismuth and antimony chalcogenide bulk topological insulators (TIs; refs ,,,), followed by closely related ternary compounds and predictions of several weak TIs (refs ,,). However, both the conceptual richness of Z2 classification of TIs as w...
The chemical potential of a superconductor is of critical importance since,
at equilibrium, it is the energy where electrons pair and form the
superconducting condensate. However, in non-equilibrium measurements, there may
be a difference between the chemical potential of the quasiparticles and that
of the pairs. Here we report a systematic time- a...
We present in-depth measurements of the electronic band structure of the
transition-metal dichalcogenides (TMDs) MoS2 and WS2 using angle-resolved
photoemission spectroscopy, with focus on the energy splittings in their
valence bands at the K point of the Brillouin zone. Experimental results are
interpreted in terms of our parallel first-principles...
We present a systematic angle-resolved photoemission spectroscopy study of
the substitution-dependence of the electronic structure of
Rb$_{0.8}$Fe$_{2}$(Se$_{1-z}$S$_z$)$_2$ (z = 0, 0.5, 1), where
superconductivity is continuously suppressed into a metallic phase. Going from
the non-superconducting Rb$_{0.8}$Fe$_{2}$(Se$_{1-z}$S$_z$)$_2$ to
superco...
We use time- and angle-resolved photoemission to measure quasiparticle
relaxation dynamics across a laser-induced superconducting phase transition in
Bi2Sr2CaCu2O8+delta. Whereas low-fluence measurements reveal picosecond
dynamics, sharp femtosecond dynamics emerge at higher fluence. Analyses of data
as a function of energy, momentum, and doping in...
We find excitations lower in energy than known phonon modes in underdoped
La$\_{2-x}$Sr$\_x$CuO$\_{4+\delta}$ (x=0.08), with both inelastic X-Ray
scattering (IXS) and inelastic neutron scattering (INS). A non dispersive
excitation at 9 meV is identified and is also seen by INS in
(La,Nd)$\_{2-x}$Sr$\_x$CuO$\_{4+\delta}$, with 40$\%$ Nd substitution...
Angle-resolved photoemission spectroscopy (ARPES) is typically used to study
only the occupied electronic band structure of a material. Here we use
laser-based ARPES to observe a feature in bismuth-based superconductors that,
in contrast, is related to the unoccupied states. Specifically, we observe a
dispersive suppression of intensity cutting acr...
We present high-resolution angle-resolved photoemission spectroscopy study in
conjunction with first principles calculations to investigate how the
interaction of electrons with phonons in graphene is modified by the presence
of Yb. We find that the transferred charges from Yb to the graphene layer
hybridize with the graphene $\pi$ bands, leading t...
Ultrafast spectroscopy is an emerging technique with great promise in the study of quantum materials, as it makes it possible to track similarities and correlations that are not evident near equilibrium. Thus far, however, the way in which these processes modify the electron self-energy-a fundamental quantity describing many-body interactions in a...
We examine the effects of the electric fields caused by the difference in work function between a sample and its surroundings in laser-based angle-resolved photoemission spectroscopy (laser ARPES) experiments. To simulate these effects we created several sample and surrounding puck geometries using SimIon 8.0 modeling software, and found that in mo...
Citations
... The spatial charge inhomogeneity brought about by the charge-donating impurities could induce an expected standing wave patterns due to the backscattering of Dirac fermions [19,20]. For twisted bilayer graphene (TBG), away from the charge neutrality point, inhomogeneous charge distribution could enhance the particle-hole asymmetry of the Drude weight, which affects the optical conductivity and plasmonic spectra [14,21,22]. The local-field effect (LFE), arises from microscopic density fluctuations due to charge variations of the Hartree potential and contributes to the non-zero off-diagonal elements of the dynamical dielectric matrix ε G,G ′ , which is pronounced in inhomogeneous-charge-distributed systems [23]. ...
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... Therefore, the goal of engineering these lattices to align a topological FB to the Fermi level (E F ) has always been an important aspect of kagome metal research [1]. Despite numerous reports on positioning other topological features like the Van Hove singularities (VHSs) [13,14,[18][19][20][21][22][23] and Dirac points at the Fermi level [10,12,[24][25][26][27][28], stabilizing a kagome lattice to bring these FBs into close proximity to the E F continues to be challenging, especially in a system with electronic orders. ...
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... [1][2][3][4] By virtue of the unique electronic band structures, topological insulators have shown great potential in both fundamental research and applied technologies. Thus far, a wealth of inspiring physical phenomena, including quantum abnormal Hall effect, 5 anomalous Hall effect, 6 ultralow power spin-orbit torque magnetization switching, 7 spatially indirect spin-polarized excitonic states, 8 high-temperature Majorana zero modes, 9 room-temperature quantum spin Hall edge state, 10 superconductivity, 11 and giant high temperature spin Hall effect, 12 have been unveiled in topological insulators and the related heterostructures. ...
... Correspondingly, there has been a recent renaissance in the study of perovskite nickelates, their metal-to-insulator transition (MIT), 12 and accompanying antiferromagnetism. 13,14 Nonetheless, the growth and reduction of NdNiO 3 thin films are not with-out their own challenges. Non-stoichiometry [15][16][17][18] and strain [19][20][21] both substantially influence the growth and properties of the precursor phase, as well as the quality of subsequently reduced films. ...
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... The authors have shown that applying a magnetic field to amorphous Bi 2 Se 3 , a typical weak anti-localization was observed in the magnetoresistance at small magnetic fields. Additionally, ARPES supports the topological state interpretation with data showing consistency with a dispersive two-dimensional surface state that crosses the bulk gap [20]. ...
... Layered VX 3 compounds are deeply investigated motivated by the technological perspectives they promise and for the peculiar physical properties they have demonstrated to host [16,26,27]. They have been recently investigated by different experimental and theoretical approaches because of contrasting evidences on the nature of their electronic ground state [16,25,[28][29][30][31]. ...
Reference: Symmetry breaking in vanadium trihalides
... When the electronic system relaxes back, the energy landscape and the equilibrium position of the oscillation follow. The extracted relaxation time of the displaced equilibrium position on roughly 300 ± 300 fs matches the fast recovery of the valence band shift that is usually interpreted as an indicator of the CDW order in 1T-TiSe 2 [23,47]. However, such a fast relaxation is unusual for displacive excitation and may hint at a more complex excitation pathway that warrants further investigation. ...
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... Several studies have addressed the possibility of visualizing exciton features in TR-ARPES theoretically using model Hamiltonians (22)(23)(24)(25)31). Quasi-equilibrium theory has also been applied to model a mixture of free carrier and bound excitons, where the spectral function shows a satellite structure due to excitons (32)(33)(34)(35). In these quasi-equilibrium models (32)(33)(34), excitons or carriers are assumed to be in equilibrium (taking advantage of the time-scale difference between electron-electron scattering and electron scattering due to other degree of freedoms), and hence cannot address the fast electron dynamics in the femtosecond time scale. ...
... Quantum wells (QW) formed in external electric fields have diverse applications from spintronics [1] to twodimensional superconductivity [2]. QW of III-V semiconductor has a linear or triangular potential profile and is known to show interesting optical properties [3]. ...
... Various mechanisms, including Jahn-Teller effects and exciton condensation, have been proposed to explain the CDW formation, yet the exact mechanism of CDW formation is still unclear and subject of many studies [7][8][9][10][11][12][13][14]. Recent experiments on ultrafast nonthermal melting of the CDW in 1T-TiSe 2 suggest that the electronic and vibrational degrees of freedom are strongly coupled in the CDW quenching process [15][16][17][18][19][20][21][22][23][24][25][26][27], and different timescales of the loss of electronic and structural orders have been observed [28,29]. ...
