Chimera states are fragile under random links (Vol. 51, No. 2)

Example of a chimera state in a ring of coupled oscillators (left) destroyed by the presence of a single random link (right).

In a chimera state of large interactive systems the underlying symmetry of the dynamical system is spontaneously broken and the spatial profile splits into synchronised and desynchronised groups.

In this work the surprising fragility of chimeras in the presence of very few time-varying random links is demonstrated in wide-ranging examples. Spatial randomness restores the symmetry of the emergent spatial patterns, with chimeras giving way to uniform steady states or spatiotemporal chaos. The size of the basin of attraction of chimeras rapidly shrinks under increasing randomness, indicating its strong impact on the global stability of chimeras. These results impact the search for chimeras in real-world systems.

Sudeshna Sinha, Chimera states are fragile under random links, EPL 128, 40004 (2019)

Spinning quantum dots (Vol. 51, No. 2)

The expectation value of the electron spin for different rotation angles in four different semiconductor materials, showing a strong pattern of beats in each case.

A theoretical analysis of electron spins in slowly moving quantum dots suggests these can be controlled by electric fields.

‘Quantum dots’ are particles of semiconducting materials that are so tiny – a few nanometres in diameter – that they no longer behave quite like ordinary, macroscopic matter. Thanks to their quantum-like optical and electronic properties, they are showing promise as components of quantum computing devices, but these properties are not yet fully understood. In this work the theory behind some of these novel properties is described in detail.

Prabhakar, S. and Melnik, R. , Berry phase and spin precession without magnetic fields in semiconductor quantum dots, European Physical Journal B 92, 263 (2019)

Laser-based prototype probes cold atom dynamics (Vol. 51, No. 2)

Apparatus for cold atom inertial sensing.

A new prototype design doubles the frequencies of widely used telecommunications lasers to study the dynamics of cold atoms while in space.

By tracking the motions of cold atom clouds, astronomers can learn much about the physical processes which play out in the depths of space. In this work, an innovative prototype for a new industrial laser system is presented that paves the way for development of cold atom inertial sensors in space.

R. Caldani, S. Merlet, F.P. Dos Santos, G. Stern, A. Martin, B. Desruelle, V. Ménoret, A prototype industrial laser system for cold atom inertial sensing in space, European Physical Journal D 73, 248 (2019)

Nano amorphous Interfaces in phase-change memory materials (Vol. 51, No. 2)

Model of nano interface between amorphous and crystalline phases in a PCM material.

Phase-change memory (PCM) is an emerging non-volatile memory technology. It encodes data through the rapid and reversible transition between amorphous and crystalline states of PCM materials.

In this work the effects of three kinds of nano amorphous interfaces in PCM materials are summarised, i.e. interfaces could either enhance phase stability (the amorphous Si/amorphous Sb2Te3 interface and the amorphous GeTe/cubic Sb2Te3 interface) or promote crystallization (the amorphous/crystalline GeSbTe interface). Therefore, these nano interfaces can be used to enhance data-retention ability or accelerate data-encoding speed.

X.-P. Wang, Y.-T. Liu, Y.-J. Chen, N.-K. Chen and X.-B. Li, Nanoscale amorphous interfaces in phase-change memory materials: structure, properties and design, J. Phys. D: Appl. Phys. 53, 114002 (2020)

mm Universe @ NIKA2 (Vol. 51, No. 2)

The NIKA2 camera opens a new area for millimeter observations of the Universe.

Conference Proceedings

NIKA2 is a millimetre camera recently installed at the 30-m telescope of IRAM. It can survey large areas of the sky at a high-angular resolution, with a high sensitivity and a large field of view. It allows observers to address questions, such as the environment impact on dust properties, the star formation processes at low and high redshifts, the evolution of the large-scale structures and the use of galaxy clusters for precision cosmology. In June 2019, the mm Universe conference in Grenoble brought together the scientific community working with the NIKA2 camera. It was the first edition in a series of conferences that will accompany the scientific exploitation of NIKA2.

F. Mayet, A. Catalano, J.F. Macías-Pérez and L. Perotto (Eds.), mm Universe @ NIKA2 - Observing the mm Universe with the NIKA2 Camera, Grenoble, France, June 3-7, 2019, EPJ Web of Conferences 228 (2020), ISBN: 978-2-7598-9097-2

Can we study the many-body localisation transition? (Vol. 51, No. 2)

Can we study the many-body localisation transition?
The timescale for delocalisation grows quickly with disorder strength.

An interacting quantum system experiencing strong disorder can undergo a transition into a non-thermalising phase: an effect known as many-body localisation (MBL).

Delocalisation transition is understood to be driven by the hybridisation of resonant many-body configurations which can only form above a certain length scale. Experimental efforts are hindered by the finite lifetimes of the system, so one cannot truly distinguish localisation from very slow dynamics. In this letter the length- and timescales required to observe thermalisation, and how they grow when approaching the MBL transition from the delocalised side are studied. The results suggest that reliably characterising the transition’s critical properties is beyond the reach of current experimental and numerical techniques.

R. K. Panda et al, Can we study the many-body localisation transition?, EPL 128 67003 (2019)