# Atomic and molecular physics

• Article
| Open Access

### Quantum state tomography of molecules by ultrafast diffraction

Ultrafast diffraction is fundamental in capturing the structural dynamics of molecules. Here, the authors establish a variant of quantum state tomography for arbitrary degrees of freedom to characterize the molecular quantum states, which will enable the reconstruction of a quantum molecular movie from diffraction data.

• Ming Zhang
• , Shuqiao Zhang
•  & Zheng Li
• Article
| Open Access

### Observing non-ergodicity due to kinetic constraints in tilted Fermi-Hubbard chains

It was predicted that complex thermalizing behaviour can arise in many-body systems in the absence of disorder. Here, the authors observe non-ergodic dynamics in a tilted optical lattice that is distinct from previously studied regimes, and propose a microscopic mechanism that is due to emergent kinetic constrains.

• Sebastian Scherg
• , Thomas Kohlert
•  & Monika Aidelsburger
• Article
| Open Access

### Controlled multi-photon subtraction with cascaded Rydberg superatoms as single-photon absorbers

Interaction of photons with Rydberg atoms can be used to modify quantum states of light. Here the authors demonstrate a controlled nonlinear quantum behavior of multi-photon subtraction in a cascaded system based on Rydberg superatoms.

• Nina Stiesdal
• , Hannes Busche
•  & Sebastian Hofferberth
• Article
| Open Access

### Observation of laser-assisted electron scattering in superfluid helium

Laser-assisted electron scattering (LAES) is a commonly observed strong field process in gas phase systems. Here the authors use helium droplets with core atoms and molecules to observe increased electron energy due to multiple LAES events within the droplets.

• Leonhard Treiber
• , Bernhard Thaler
•  & Markus Koch
• Article
| Open Access

### Ultrafast imaging of spontaneous symmetry breaking in a photoionized molecular system

The Jahn-Teller effect is the spontaneous symmetry breaking of the molecular structure caused by the coupling of electrons and nuclei. Here the authors use ultrafast Coulomb explosion imaging to map the evolution of the fundamental symmetry lowering process in photoionized methane within around 20fs.

• Min Li
• , Ming Zhang
•  & Peixiang Lu
• Article
| Open Access

### Fast-field-cycling ultralow-field nuclear magnetic relaxation dispersion

Nuclear spin polarization and relaxation can be studied using nuclear magnetic resonance (NMR). Here the authors demonstrate a combination of fast-field cycling and optical magnetometry techniques, to realize a NMR sensor that operates in the region of very low frequency and high relaxation rate.

• Sven Bodenstedt
• , Morgan W. Mitchell
•  & Michael C. D. Tayler
• Article
| Open Access

### Enantio-sensitive unidirectional light bending

Developing new methods for structuring light’s chirality in space would be advantageous for various next-generation applications. Here, the authors report enantio-sensitive unidirectional light bending by interacting light with isotropic chiral media.

• David Ayuso
• , Andres F. Ordonez
•  & Olga Smirnova
• Article
| Open Access

### Diffusive-like redistribution in state-changing collisions between Rydberg atoms and ground state atoms

Here, the authors discuss state-changing inelastic collisions between rubidium Rydberg and ground state atoms. They employ high-resolution magneto-optical trap recoil-ion momentum spectroscopy to measure the distribution of the final states.

• Philipp Geppert
• , Max Althön
•  & Herwig Ott
• Article
| Open Access

### Correlator convolutional neural networks as an interpretable architecture for image-like quantum matter data

Physical principles underlying machine learning analysis of quantum gas microscopy data are not well understood. Here the authors develop a neural network based approach to classify image data in terms of multi-site correlation functions and reveal the role of fourth-order correlations in the Fermi-Hubbard model.

• Cole Miles
• , Annabelle Bohrdt
•  & Eun-Ah Kim
• Article
| Open Access

### Anomalous formation of trihydrogen cations from water on nanoparticles

The H3+ ion plays a key role in interstellar chemistry and can be formed from organic compounds upon interaction with charged particles or radiation. Here the authors demonstrate that H3+ can also be formed from water adsorbed on silica nanoparticles exposed to intense laser pulses, conditions that mimic the impact of charged particles on dust in astrophysical settings.

• M. Said Alghabra
• , Rami Ali
•  & Ali S. Alnaser
• Article
| Open Access

### Room-temperature single-photon source with near-millisecond built-in memory

Room-temperature single photon sources with memory capabilities are promising for quantum information processing, but are currently limited in their memory time or photon purity. Here, the authors report single photon emission with good antibunching from an atomic vapour cell source with 0.68 ms memory time.

• Karsten B. Dideriksen
• , Rebecca Schmieg
•  & Eugene S. Polzik
• Article
| Open Access

### Attosecond intra-valence band dynamics and resonant-photoemission delays in W(110)

Accessing intraband dynamics is challenging due to simultaneous requirements on energy, momentum and time resolution. Here, the authors measure intraband delays between sp- and d-band electronic states in the valence band photoemission from W(110) using intracavity generated attosecond pulse trains.

• S. Heinrich
• , T. Saule
•  & U. Kleineberg
• Article
| Open Access

### Photon bubble turbulence in cold atom gases

Photon bubble turbulence is an astrophysical phenomenon involving radiation transport. Here, the authors report analogous behavior in ultracold gas by observing signatures of photon bubble instabilities in Rb atoms trapped in a MOT.

• R. Giampaoli
• , João D. Rodrigues
•  & J. T. Mendonça
• Article
| Open Access

### Unravelling the electron injection/transport mechanism in organic light-emitting diodes

Understanding the role electron injection and transport in organic light-emitting diodes (OLED) is critical for optimizing device performance. Here, the authors elucidate the electron injection/transport mechanism in OLEDs and identify the cathode/emissive layer energy barrier as the key factor.

• Tsubasa Sasaki
• , Munehiro Hasegawa
•  & Hirohiko Fukagawa
• Article
| Open Access

### Twin-lattice atom interferometry

Atom interferometers can be useful for precision measurement of fundamental constants and sensors of different type. Here the authors demonstrate a compact twin-lattice atom interferometry exploiting Bose-Einstein condensates (BECs) of 87 Rb atoms.

• Martina Gebbe
• , Jan-Niclas Siemß
•  & Ernst M. Rasel
• Article
| Open Access

### Precisely spun super rotors

Optical pulses can be useful to create and control molecules in higher quantum states. Here the authors use optical pumping to create rotationally excited states of SiO+ molecular ion into super rotor ensemble.

• Ivan O. Antonov
• , Patrick R. Stollenwerk
•  & Brian C. Odom
• Article
| Open Access

### A quantum heat engine driven by atomic collisions

Designing reliable nanoscale quantum-heat engines achieving high efficiency, high power and high stability is of fundamental and practical interest. Here, the authors report the realization of such a quantum machine using individual neutral Cs atoms in an atomic Rb bath, in which quantized heat exchange via inelastic spin-exchange collisions is controlled at the level of single quanta.

• Quentin Bouton
• , Jens Nettersheim
•  & Artur Widera
• Article
| Open Access

### Heuristic machinery for thermodynamic studies of SU(N) fermions with neural networks

The detection of the effects of spin symmetry in momentum distribution of an SU(N)-symmetric Fermi gas has remained challenging. Here, the authors use supervised machine learning to connect the spin multiplicity to thermodynamic quantities associated with different parts of the momentum distribution.

• Entong Zhao
• , Jeongwon Lee
•  & Gyu-Boong Jo
• Article
| Open Access

### Angular dependence of the Wigner time delay upon tunnel ionization of H2

Light-matter interaction leading to photoelectron emission via the photoelectric effect illustrates the quantum nature of light. Here, the authors report the dependence of the photoelectron’s Wigner time delay on the photoelectron’s emission direction relative to the molecular axis of hydrogen in strong field tunnel-ionization.

• D. Trabert
• , S. Brennecke
•  & S. Eckart
• Article
| Open Access

### Ultrafast multi-cycle terahertz measurements of the electrical conductivity in strongly excited solids

The electrical conductivity is critical to understand warm dense matter, but the accurate measurement is extremely challenging. Here the authors use multi-cycle THz pulses to measure the conductivity of gold foils strongly heated by free-electron laser, determining the individual contributions of electron-electron and electron-ion scattering.

• Z. Chen
• , C. B. Curry
•  & S. H. Glenzer
• Article
| Open Access

### Evolution and universality of two-stage Kondo effect in single manganese phthalocyanine molecule transistors

The Kondo effect can serve as a powerful paradigm to understand strongly correlated many-body processes in physics. Here, Guo et al. utilize single molecule transistor devices as a testbed to study multi-level Kondo correlation and show electrical gate evolution and the universality of the two-stage Kondo effect.

• Xiao Guo
• , Qiuhao Zhu
•  & Wenjie Liang
• Article
| Open Access

### Molecular structure retrieval directly from laboratory-frame photoelectron spectra in laser-induced electron diffraction

Optical methods utilizing ultrashort laser pulses are commonly used to probe structure and dynamics of atoms and molecules. Here the authors report a method which uses critical points and is capable of extracting molecular structure with picometer spatial and attosecond temporal resolution.

• A. Sanchez
• , K. Amini
•  & J. Biegert
• Article
| Open Access

### Large optical nonlinearity enhancement under electronic strong coupling

Nonlinear optical response of the material plays a crucial role in light-matter interactions and is important for practical applications. Here, the authors report enhancement of optical nonlinearity of J-aggregate cyanine molecules due to strong coupling between the molecules and an optical cavity.

• Kuidong Wang
• , Marcus Seidel
•  & Thomas Ebbesen
• Article
| Open Access

### Ultracold atom interferometry in space

Conducting atom-optical experiments in space is interesting for fundamental physics and challenging due to different environment compared to ground. Here the authors report matter-wave interferometry in space using atomic BECs in a sounding rocket.

• Maike D. Lachmann
• , Holger Ahlers
•  & Ernst M. Rasel
• Article
| Open Access

### Observation of a quantum phase transition in the quantum Rabi model with a single trapped ion

Quantum phase transition occurs in many-body systems with abrupt changes in the ground state around zero temperature. Here the authors report signatures of quantum phase transition in single trapped ion that can be described using quantum Rabi model.

• M.-L. Cai
• , Z.-D. Liu
•  & L.-M. Duan
• Article
| Open Access

### Tan’s two-body contact across the superfluid transition of a planar Bose gas

Here the authors use Ramsey interferometry to study Tan’s contact in uniform two-dimensional Bose gas of 87Rb atoms across the Berezinskii–Kosterlitz–Thouless superfluid transition. They find that the two-body contact is continuous across the critical point.

• Y.-Q. Zou
• , B. Bakkali-Hassani
•  & J. Beugnon
• Article
| Open Access

### Coherent characterisation of a single molecule in a photonic black box

The authors develop a method to measure the coupling between a single photon source and any arbitrary photonic structure having constant density of electromagnetic states over the linewidth of the emitter. They demonstrate this method by an experiment on a single molecule coupled to an interrupted nanophotonic waveguide.

• Sebastien Boissier
• , Ross C. Schofield
•  & Alex S. Clark
• Article
| Open Access

### Ultrafast electron cooling in an expanding ultracold plasma

Here the authors report on the creation of ultracold plasma by photoionization of a Bose-Einstein condensate with a femtosecond laser pulse. The experimental setup grants direct access to the electron temperature and reveals ultrafast cooling of electrons in an initially strongly coupled plasma.

• Tobias Kroker
• , Mario Großmann
•  & Juliette Simonet
• Article
| Open Access

### Dynamical strengthening of covalent and non-covalent molecular interactions by nuclear quantum effects at finite temperature

The inclusion of nuclear quantum effects (NQE) in atomistic simulations of chemical systems is of key importance. Here the authors use machine learned force fields trained on coupled cluster reference data to show the dynamical strengthening of covalent and non-covalent molecular interactions induced by NQE.

• Huziel E. Sauceda
• , Valentin Vassilev-Galindo
•  & Alexandre Tkatchenko
• Article
| Open Access

### Kibble-Zurek exponent and chiral transition of the period-4 phase of Rydberg chains

Phase transition occurring in quantum material is an intriguing phenomenon. Here, the authors discuss the commensurate-incommensurate phase transition out of the period-4 phase on a chain of Rydberg atoms and emphasize the emergence of a chiral transition.

• Natalia Chepiga
•  & Frédéric Mila
• Article
| Open Access

### Excited-state vibration-polariton transitions and dynamics in nitroprusside

Here the authors report spectroscopy and dynamics of cavity coupled NO band of sodium nitroprusside using 2D infrared and transient spectroscopy employing pump-probe technique. They find signatures of third-order nonlinearity, incoherent and strong coupling effects of vibrational polaritons.

• Andrea B. Grafton
•  & Jeffrey C. Owrutsky
• Article
| Open Access

### Single ion qubit with estimated coherence time exceeding one hour

Extending qubit coherence times represent one of the key challenges for quantum technologies. Here, after properly suppressing magnetic-field fluctuations, frequency instability and leakage of the microwave reference-oscillator, the authors infer coherence times of 5500 s for an Yb ion qubit.

• Pengfei Wang
• , Chun-Yang Luan
•  & Kihwan Kim
• Article
| Open Access

### Epidemic growth and Griffiths effects on an emergent network of excited atoms

The emergent excitation dynamics of an ultracold gas of Rydberg atoms exhibits features analogous to epidemic spreading on networks. Wintermantel et al. propose a controllable experimental system for studying network dynamics at the interface of mathematical models and real-world complex systems.

• T. M. Wintermantel
• , M. Buchhold
•  & S. Whitlock
• Article
| Open Access

### Split-pulse X-ray photon correlation spectroscopy with seeded X-rays from X-ray laser to study atomic-level dynamics

Here the authors study atomic scale dynamics in water by using X-ray photon correlation spectroscopy. They use a split-and-delay optics with self-seeding of X-rays to generate pulses of enough energy and controlled time delay between two X-ray pulses.

• Yuya Shinohara
• , Taito Osaka
•  & Takeshi Egami
• Article
| Open Access

### Prospects and challenges for squeezing-enhanced optical atomic clocks

Optical atomic clocks are useful tools for frequency metrology. Here the authors explore the stability of the atomic clocks and the role of the spin squeezed states for the noise reduction in these clocks.

• Marius Schulte
• , Christian Lisdat
•  & Klemens Hammerer
• Article
| Open Access

### Non-Abelian Bloch oscillations in higher-order topological insulators

Bloch oscillations (BO) are intrinsically related to the geometry and topological properties of the underlying band structure. Here, Di Liberto et al. predict a unique topological effect manifested in the BOs of higher-order topological insulators through the interplay of non-Abelian Berry curvature and quantized Wilson loops.

• M. Di Liberto
• , N. Goldman
•  & G. Palumbo
• Article
| Open Access

### A possible route towards dissipation-protected qubits using a multidimensional dark space and its symmetries

To design and manipulate qubits, it is necessary to engineer multidimensional non-equilibrium steady states immune to decoherence in an open system. Here the authors devise a symmetry-based framework to create such non-equilibrium steady states showing characteristics of degenerate vacua of a unitary topological system.

• Raul A. Santos
• , Fernando Iemini
•  & Yuval Gefen
• Article
| Open Access

### Observation of nanoscale opto-mechanical molecular damping as the origin of spectroscopic contrast in photo induced force microscopy

Existing high-dimensional optical imaging techniques that record space and polarization cannot detect the photon’s time of arrival due to the limited speeds of electronic sensors. Here, the authors develop a single-shot ultrafast imaging modality to record light-speed high-dimensional events with picosecond resolution.

• , Syed Mohammad Ashab Uddin
•  & H. Kumar Wickramasinghe
• Article
| Open Access

### Retrodiction beyond the Heisenberg uncertainty relation

If we have access to information about a quantum system both before and after a measurement, we are not in the usual remit of the Heisenberg uncertainty principle anymore. Here, the authors demonstrate that, in such a scenario, one can retrodict position and momentum measurements without being limited by HUR.

• Han Bao
• , Shenchao Jin
•  & Yanhong Xiao
• Article
| Open Access

### Electron tunneling at the molecularly thin 2D perovskite and graphene van der Waals interface

Insulating molecular layers on the basal plane of 2D perovskite is a major bottleneck for charge injection that limiting device performance. Here, the authors show that plane-contacted graphene functions as a low barrier and gate-tunable contact to overcome this limitation.

• Kai Leng
• , Lin Wang
•  & Kian Ping Loh
• Article
| Open Access

### Large array of Schrödinger cat states facilitated by an optical waveguide

Light-atom interactions allow exotic atomic states that could enable quantum applications for communication or metrology. Here, the authors load a large 1D array of atoms in a hollow-core photonic crystal fibre, each one prepared in an entangled state of its electronic and motional states.

• Wui Seng Leong
• , Mingjie Xin
•  & Shau-Yu Lan
• Article
| Open Access

### Attosecond electron–spin dynamics in Xe 4d photoionization

Here the authors report experiment and theory study of the photoionization of xenon inner shell 4d electron using attosecond pulses. They have identified two ionization paths - one corresponding to broad giant dipole resonance with short decay time and the other involving spin-flip transitions.

• Shiyang Zhong
•  & Anne L’Huillier
• Article
| Open Access

### Identification of molecular quantum states using phase-sensitive forces

The identification of molecular quantum states becomes challenging with increasing complexity of the molecular level structure. Here, the authors non-destructively identified excited molecular states of the $${{\rm{N}}}_{2}^{+}$$ ${\mathrm{N}}_{2}^{+}$ by interfering forces applied to both the molecular ion and to a co-trapped atomic ion.

• Kaveh Najafian
• , Ziv Meir
•  & Stefan Willitsch
• Article
| Open Access

### Delocalization of exciton and electron wavefunction in non-fullerene acceptor molecules enables efficient organic solar cells

Y6, as a non-fullerene acceptor for organic solar cells, has attracted intensive attention because of the low voltage loss and high charge generation efficiency. Here, Zhang et al. find that the delocalization of exciton and electron wavefunction due to strong π-π packing of Y6 is the key for the high performance.

• Guichuan Zhang
• , Xian-Kai Chen
•  & Yong Cao
• Article
| Open Access

### Direct observation of a Feshbach resonance by coincidence detection of ions and electrons in Penning ionization collisions

Here the authors use ion-electron coincidence imaging method to explore collision dynamics. They observe Feshbach resonance in the Penning ionization collision of argon and excited helium atoms, resulting in singly charged argon ion and ground state helium.

• Baruch Margulis
• , Julia Narevicius
•  & Edvardas Narevicius
• Article
| Open Access

### Light phase detection with on-chip petahertz electronic networks

On-chip optical-field emission devices may be useful for fast electronics and signal processing. Here the authors show a compact on-chip light phase detector capable of monitoring photocurrents oscillating at optical frequencies using electrically connected arrays of plasmonic bow-tie nanoantennae.

• Yujia Yang
• , Marco Turchetti
•  & Phillip D. Keathley
• Article
| Open Access

### Quantum interference of currents in an atomtronic SQUID

Quantum interference of currents was first observed in a superconducting quantum interference device (SQUID). Here, the authors demonstrate quantum interference of currents in the atomtronic analog of a SQUID using Bose-Einstein condensates of 87Rb atoms.

• C. Ryu
• , E. C. Samson
•  & M. G. Boshier
• Article
| Open Access

### Strongly correlated Fermions strongly coupled to light

Atom-photon interaction and their coupling are important to understand correlated and quantum matter. Here the authors show strong coupling between degenerate interacting Fermi gas of 6Li atoms and photons.

• Kevin Roux
• , Hideki Konishi
•  & Jean-Philippe Brantut
• Article
| Open Access

### Heavy N+ ion transfer in doubly charged N2Ar van der Waals cluster

There are multiple ways by which energy and charge transfer occur in weakly bound systems. Here the authors reveal a heavy ion N+ transfer in a doubly charged Van der Waals cluster produced in collisions of the highly charged Ne8+ ion with N2Ar, leading to fragmentation of N+ and NAr+ via Coulomb explosion.

• XiaoLong Zhu
• , XiaoQing Hu
•  & X. Ma
• Perspective
| Open Access

### Attosecond science based on high harmonic generation from gases and solids

Different methods are demonstrated in recent years to produce attosecond pulses. Here, the authors discuss recent development and future prospects of the generation of such pulses from gases and solids and their potential applications in spectroscopy and ultrafast dynamics in atoms, molecules and other complex systems.

• Jie Li
• , Jian Lu
•  & Zenghu Chang