A5042199927- Physics of Superconductivity and Magnetism
- Multiferroics and related materials
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Magnetic properties of thin films
- Ferroelectric and Piezoelectric Materials
- Electronic and Structural Properties of Oxides
- Quantum and electron transport phenomena
- High-pressure geophysics and materials
- Topological Materials and Phenomena
- Mechanical and Optical Resonators
- Quantum, superfluid, helium dynamics
- Acoustic Wave Resonator Technologies
- Advanced Fiber Laser Technologies
- Spectroscopy and Quantum Chemical Studies
- Advanced Thermoelectric Materials and Devices
- Organic and Molecular Conductors Research
- Iron-based superconductors research
- Advanced Chemical Physics Studies
- Cold Atom Physics and Bose-Einstein Condensates
- Inorganic Fluorides and Related Compounds
- Photonic and Optical Devices
- Geophysics and Sensor Technology
- Diamond and Carbon-based Materials Research
- Photorefractive and Nonlinear Optics
Max Planck Institute for the Structure and Dynamics of Matter
2017-2025
Universität Hamburg
2018-2025
Center for Free-Electron Laser Science
2025
ETH Zurich
2012-2024
Max Planck Society
1993-2021
Diamond Light Source
2017
Max Planck Institute for Solid State Research
2017
University of Oxford
2017
SLAC National Accelerator Laboratory
2017
Linac Coherent Light Source
2017
Driving strontium titanate ferroelectric Hidden phases are metastable collective states of matter that typically not accessible on equilibrium phase diagrams. Nova et al. used infrared pulses to excite higher-frequency lattice modes drive the crystal into a phase, can persist for many hours. X. Li terahertz fields soft mode moves ions in positions they occupy new phase. The this case was transient, lasting order 10 picoseconds. Because these hidden host exotic properties otherwise...
In many multiferroic materials, the ferroelectric polarization is induced by a spatially varying magnetization such as spin spiral. Here authors introduce reciprocal effect, in which time-dependent electric induces even previously nonmagnetic materials. The illustrate this dynamical effect with four examples---the phonon Zeeman optical excitation of magnons and electromagnons, inverse Faraday effect---which they investigate using combination density functional theory, microscopic...
Abstract In quantum materials, degeneracies and frustrated interactions can have a profound impact on the emergence of long-range order, often driving strong fluctuations that suppress functionally relevant electronic or magnetic phases 1–7 . Engineering atomic structure in bulk at heterointerfaces has been an important research strategy to lift these degeneracies, but equilibrium methods are limited by thermodynamic, elastic chemical constraints 8 Here we show all-optical, mode-selective...
Abstract Crystal lattice fluctuations, which are known to influence phase transitions of quantum materials in equilibrium, also expected determine the dynamics light-induced changes. However, they have only rarely been explored these dynamical settings. Here we study time evolution fluctuations paraelectric SrTiO 3 , mid-infrared drives shown induce a metastable ferroelectric state. Crucial physics is competition between polar instabilities and antiferrodistortive rotations, equilibrium...
Chirality, a pervasive form of symmetry, is intimately connected to the physical properties solids, as well chemical and biological activity molecular systems. However, inducing chirality in nonchiral material challenging because this requires that all mirrors roto-inversions be simultaneously broken. Here, we show either handedness can induced piezoelectric boron phosphate (BPO 4 ) by irradiation with terahertz pulses. Resonant excitation one two orthogonal, degenerate vibrational modes...
We develop the formalism of macroscopic monopolization -- that is monopole moment per unit volume in periodic solids, and discuss its relationship to diagonal magnetoelectric effect. For series lithium transition metal phosphate compounds we use first-principles density functional theory calculate contributions from global distribution magnetic moments within cell, as well magnetization around atomic sites. find one example (LiMnPO$_4$) shows a corresponding ferromonopolar ordering...
Superconductivity in organic conductors is often tuned by the application of chemical or external pressure. With this type tuning, orbital overlaps and electronic bandwidths are manipulated, whilst properties molecular building blocks remain virtually unperturbed.Here, we show that excitation local vibrations charge-transfer salt $\kappa-(BEDT-TTF)_2Cu[N(CN)_2]Br$ induces a colossal increase carrier mobility opening superconducting-like optical gap. Both features track density...
We describe a mechanism by which nonlinear phononics allows ultrafast coherent and directional control of transient structural distortions. With ${\text{ErFeO}}_{3}$ as model system, we use density functional theory to calculate the properties input into an anharmonic phonon that describes response system pulsed optical excitation. find trilinear coupling two orthogonal infrared-active phonons Raman-active causes distortion lattice. In contrast quadratic-linear has been previously explored,...
Abstract Nonlinear phononics relies on the resonant optical excitation of infrared-active lattice vibrations to induce targeted structural deformations in solids. This form dynamical crystal structure design has been applied control functional properties many complex solids, including magnetic materials, superconductors and ferroelectrics. However, so far restricted protocols which occur within optically excited volume, sometimes resulting unwanted heating. Here, we extend nonlinear...
Abstract Photo-excitation at terahertz and mid-infrared frequencies has emerged as an effective way to manipulate functionalities in quantum materials, some cases creating non-equilibrium phases that have no equilibrium analogue. In K 3 C 60 , a metastable zero-resistance phase was observed optical properties, nonlinear electrical transport pressure dependencies compatible with high-temperature superconductivity. Here we demonstrate two-orders-of-magnitude increase photo-susceptibility near...
On the basis of first-principles electronic-structure calculations we predict that epitaxial multiferroic films---fabricated as ultrathin Fe films deposited on ${\text{TiO}}_{2}$-terminated (001) surfaces $A{\text{TiO}}_{3}$ perovskites $(A=\text{Pb},\text{Ba})$---exhibit an unexpected change in their magnetic structure with increasing Fe-film thickness. The order changes from ferromagnetic, a magnetization about $3{\ensuremath{\mu}}_{B}/\text{atom}$ for 1 ML system, to ferrimagnetic almost...
We present an experimental and theoretical study of the geometric structure ultrathin BaTiO(3) films grown on Fe(001). Surface x-ray diffraction reveals that are terminated by a BaO layer, while TiO(2) layer is next to top Fe layer. Cations in termination layers have incomplete oxygen shells inducing strong vertical relaxations. Onset polarization observed at minimum thickness two unit cells. Our findings supported first-principles calculations providing quantitative insight into...
Magnetoelectric coupling allows for manipulating the magnetization by an external electric field or electrical polarization magnetic field. Here, we propose a mechanism to electrically induce 180° switching combining two effects: magnetoelectric at multiferroic interface and interlayer exchange coupling. By means of first-principles methods, investigate ferroelectric layer in contact with Fe/Au/Fe trilayer. The calculations show that magnetism is strongly coupled layer. Furthermore, under...
Amplification of light through stimulated emission or nonlinear optical interactions has had a transformative impact on modern science and technology. The amplification other bosonic excitations, like phonons in solids, is likely to open up new remarkable physical phenomena. Here, we report an experimental demonstration phonon amplification. A coherent mid-infrared field used drive large amplitude oscillations the Si-C stretching mode silicon carbide. Upon excitation, second probe pulse...
The (001) surfaces of polar perovskites $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ and $\mathrm{Pb}\mathrm{Ti}{\mathrm{O}}_{3}$ have been studied from first principles at $T=0\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. For both cases polarization, the most stable TiO-terminated interfaces show intrinsic ferroelectricity. In topmost layer, where O atoms are $>0.1\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ above Ti, this leads to metallic instead insulating behavior electronic states that may...
We use symmetry analysis and first-principles calculations to show that the linear magnetoelectric effect can originate from response of orbital magnetic moments polar distortions induced by an applied electric field. Using LiFePO(4) as a model compound we spin-orbit coupling partially lifts quenching 3d orbitals causes small (μ((L)) ≈ 0.3 μ(B)) parallel spins Fe(2+) ions. An field E modifies size these inducing net magnetization in E.
Unconventional superconductivity in the cuprates emerges from, or coexists with, other types of electronic order. However, these orders are sometimes invisible because their symmetry. For example, possible existence superfluid charge stripes normal state single layer cannot be validated with infrared optics, interlayer tunneling fluctuations vanish on average. Similarly, it is not easy to establish if responsible for dynamical decoupling superconducting layers over broad ranges doping and...
We introduce a mechanism in which coupling between fluctuating spin magnetic dipole moments and polar optical phonons leads to nonzero ferroic ordering of quasistatic magnetoelectric multipoles. Using first-principles calculations within the $\mathrm{LSDA}+U$ method density functional theory, we calculate magnitude effect for prototypical cuprate superconductor ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4}$. show that our proposed is consistent, knowledge, with all experimental data onset pseudogap...
We investigate the structural modulations induced by optical excitation of a polar phonon mode in ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ using first-principles calculations based on density functional theory. focus intense-excitation regime which we expect that fourth-order phonon-phonon coupling terms dominate and model pulses such intensity. Our anharmonicities confirm cubic between modes, shown earlier work to cause quasistatic change apical O-Cu distance buckling...