View from the arXiv: Jan 3-7 2022

Welcome to the first post of a new series, titled ‘View from the arXiv’, where each week I’ll put together a short list of new preprints which have appeared on arxiv.org during the week which I’ve found interesting. I’ll focus on the categories ‘Disordered Systems and Neural Networks’, ‘Quantum Gases’ and ‘Strongly Correlated Electrons’, and in particular the first two as these are the main areas of the arXiv which I follow. This is an entirely subjective list of things which appeal to me, and of course there are far too many interesting papers to be able cover all of them so I just choose one or two from each day to highlight here. As these are all preprints which have not yet been peer-reviewed, remember to take any claims and conclusions with a grain of salt and be sure to cast a critical eye over the work if you’re interested in more details. (And let’s face it, this caveat should be applied to any published work too…!)

Jan 3rd

Inhomogeneous disordering at a photo-induced CDW transition, by Antonio Picano, Francesco Grandi, and Martin Eckstein: In this work, the authors use a non-equilibrium generalization of statistical dynamical mean-field theory to study the relatively new phenomenon of ‘ultrafast imhomogeneous disordering’, where strong local fluctuations lead to the situation where the mean value of a given order parameter is no longer representative of the microscopic state of the system.

Jan 4th

MBL and topological order in disordered interacting Ising-Majorana chains, by Nicolas Laflorencie, Gabriel Lemarié, and Nicolas Macé: Many-body localization (MBL) is a topic that has been extensively studied over the last decade, but a lot of open questions and surprises still remain. This remarkable work uses exact numerical simulations to study the localization properties of Majorana modes in Ising-Majorana spin chains, providing evidence for two different MBL regimes, corresponding to an MBL paramagnet and an MBL spin glass respectively, separated by a broad ergodic region which intervenes between the two localized phases.

Matrix Product States with Backflow correlations, by Guglielmo Lami, Giuseppe Carleo, and Mario Collura: The language of Matrix Product States (MPS) has become one of the central pillars of modern numerical methods for the study of many-body quantum systems, and this work represents an interesting evolution of the idea, incorporating the so-called ‘backflow correlations’ to improve the descriptive power of MPS methods, allowing them to encode much more highly entangled states than earlier methods, opening up some intriguing possibilities for the study of challenging many-body systems in both one and two dimensions.

Jan 5th

Observation of unconventional many-body scarring in a quantum simulator, by Guo-Xian Su, Hui Sun, Ana Hudomal, Jean-Yves Desaules, Zhao-Yu Zhou, Bing Yang, Jad C. Halimeh, Zhen-Sheng Yuan, Zlatko Papić, and Jian-Wei Pan: Many-body scars are a fascinating example of a way in which many-body quantum systems can escape thermalisation, and this work represents an interesting step forward in the experimental ability to investigate quantum scars, here by using a Bose-Hubbard quantum simulator to realise the so-called PXP model commonly studied in the context of quantum scars. The authors also provide evidence that many-body scars can be seen in a much broader range of initial states than previously realised, by making use of detuning and periodic drive, paving the way for further exploration of this exotic phenomena in a range of experimental and theoretical environments.

Escaping many-body localization in an exact eigenstate, by N. S. Srivatsa, Michael Iversen, and Anne E. B. Nielsen: While quantum scars are special states which remain localized despite the bulk of the states exhibiting thermalisation, this work considers the opposite effect, namely a situation where the majority of quantum states are many-body localized but certain special states manage to escape localization, leading to a very unusual situation governed by some intriguing physics.

Jan 6th

Low energy excitations of mean-field glasses, by Silvio Franz, Flavio Nicoletti, and Federico Ricci-Tersenghi: One question that interests me a lot at the moment is the connection between many-body localization (a property of highly excited states) and glassy physics (a property of low energy states), and in particular the question of how excitations from glassy ground states behave. By studying the p-spin model (something I’ve worked on myself in the past), the authors of this work provide a glimpse into the behaviour of the low-energy excitations from glassy ground states, an important step shedding light on the intriguing question of how the excitations of quantum spin glasses could connect to MBL.

Jan 7th

Cluster Mean Field plus Density Matrix Renormalization theory for the Bose Hubbard Model, by Pallavi P. Gaude, and Ananya Das, Ramesh V. Pai: The Bose-Hubbard model is a rich theoretical model which describes interacting bosons on a lattice, but can be computationally difficult to solve due to bosons not obeying a Pauli exclusion principle and therefore having a much larger number of possible states than analagous fermionic models, which presents a challenge for numerically exact methods as the memory requirements for simulations increases sharply with system size. This intriguing work is an attempt to combine the flexibility and simplicity of cluster mean-field methods with the numerical power of density matrix renormalization group, which could have some interesting uses for exotic models which are beyond the reach of exact tensor network techniques.