The Editors of Physical Review Materials are pleased to present the Collection on Defect Phases in Materials, highlighting cutting-edge developments in characterizing, engineering, and optimizing defect phases for next-generation functional and structural materials. The Collection is being guest-edited by Irene Beyerlein of University of California, Santa Barbara (USA), Su-Huai Wei of Eastern Institute of Technology (China), and Sandra Korte-Kerzel of RWTH Aachen University (Germany). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

Editors of Physical Review Materials are pleased to present the Collection on Altermagnetic and Related Materials, highlighting cutting-edge advances in theoretical and experimental identification of novel altermagnetic materials, their properties, and their potential applications. The Collection is being guest-edited by Kirill Belashchenko of the University of Nebraska-Lincoln (USA), Cheng Song of Tsinghua University (China), and Peter Wadley of The University of Nottingham (UK). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on Advances in Computational Methods for Materials Research, highlighting cutting-edge developments in modeling, prediction, and interpretation of materials behavior. The Collection is being guest-edited by Axel Gross of Ulm University (Germany), Seán Kavanagh of the University of Cambridge (UK), and Shiyou Chen of Fudan University (China). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on Quantum Phenomena in Kagome Materials, highlighting cutting-edge advances in theory, synthesis, properties and applications of kagome materials. The Collection is being guest-edited by Mingda Li (MIT), Xiangang Wan (Nanjing University) and Linda Ye (Caltech). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on Functional Materials Through Electrochemical Ion Insertion, highlighting cutting-edge advances in the theory, synthesis, and structural and physical characterization of dynamic property modulation (e.g. optical, electrical, mechanical, chemical) using electrochemical ion insertion into solid state hosts. The Collection is being guest-edited by Veronica Augustyn and Nina Balke of North Carolina State University (USA). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on Machine Learning for Materials Discovery and Understanding, highlighting cutting-edge advances in machine learning method development and applications for materials discovery and fundamental understanding of the structure-property-function relationship. The Collection is being guest-edited by Deyu Lu of Brookhaven National Laboratory (USA) and Jinlan Wang of Southeast University (China). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on New Insights into Functional Materials through Advanced Electron Microscopy, highlighting cutting-edge microscopy techniques and the extraordinary advances in materials science and engineering that they enable. The Collection is being guest-edited by Joanne Etheridge from Monash University (Australia) and Yimei Zhu from Brookhaven National Laboratory (USA). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on Magnetic Phenomena at Oxide Interfaces, highlighting cutting-edge advances in oxide interface magnetism and its applications. The Collection is being guest-edited by Lucas Caretta from Brown University (USA) and Jacobo Santamaria from Universidad Complutense de Madrid (Spain). Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers. The Physical Review Materials editorial team managed the peer review and made all editorial decisions.

The Editors of Physical Review Materials are pleased to present the Collection on Self-Assembly of Complex Phases in Block Copolymer Materials, highlighting one of the most exciting fields in polymer science. Block copolymers offer an excellent model system for comprehending symmetry breaking in soft matter, as well as a unique platform for designing nanostructured materials. This Collection is being guest-edited by Kevin Dorfman from the University of Minnesota and Chris Bates from the University of California - Santa Barbara.

Physical Review Applied and Physical Review Materials are pleased to present the Collection on Two-dimensional Materials and Devices, highlighting one of the most interesting fields in Applied Physics and Materials Research. Papers belonging to this collection will be published throughout 2020. The invited articles, and an editorial by the Guest Editor, David Tománek, are linked below.