{"title":"High-Order Van Hove Singularities and Their Connection to Flat Bands","authors":"Laura Classen, Joseph J. Betouras","doi":"10.1146/annurev-conmatphys-042924-015000","DOIUrl":"https://doi.org/10.1146/annurev-conmatphys-042924-015000","url":null,"abstract":"The flattening of single-particle band structures plays an important role in the quest for novel quantum states of matter owing to the crucial role of interactions. Recent advances in theory and experiment made it possible to construct and tune systems with nearly flat bands, ranging from graphene multilayers and moiré materials to kagome metals and ruthenates. Although theoretical models predict exactly flat bands under certain ideal conditions, evidence was provided that these systems host high-order Van Hove points, i.e., points of high local band flatness and power-law divergence in energy of the density of states. In this review, we examine recent developments in engineering and realizing such weakly dispersive bands. We focus on high-order Van Hove singularities and explore their connection to exactly flat bands. We provide classification schemes and discuss interaction effects. We also review experimental evidence for high-order Van Hove singularities and point out future research directions.","PeriodicalId":7925,"journal":{"name":"Annual Review of Condensed Matter Physics","volume":"21 1","pages":""},"PeriodicalIF":22.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142643013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Charles S. Wright, Kunaal Joshi, Rudro R. Biswas, Srividya Iyer-Biswas
{"title":"Emergent Simplicities in the Living Histories of Individual Cells","authors":"Charles S. Wright, Kunaal Joshi, Rudro R. Biswas, Srividya Iyer-Biswas","doi":"10.1146/annurev-conmatphys-032822-035238","DOIUrl":"https://doi.org/10.1146/annurev-conmatphys-032822-035238","url":null,"abstract":"Organisms maintain the status quo, holding key physiological variables constant to within an acceptable tolerance, and yet adapt with precision and plasticity to dynamic changes in externalities. What organizational principles ensure such exquisite yet robust control of systems-level “state variables” in complex systems with an extraordinary number of moving parts and fluctuating variables? Here, we focus on these issues in the specific context of intra- and intergenerational life histories of individual bacterial cells, whose biographies are precisely charted via high-precision dynamic experiments using the SChemostat technology. We highlight intra- and intergenerational scaling laws and other “emergent simplicities” revealed by these high-precision data. In turn, these facilitate a principled route to dimensional reduction of the problem and serve as essential building blocks for phenomenological and mechanistic theory. Parameter-free data-theory matches for multiple organisms validate theory frameworks and explicate the systems physics of stochastic homeostasis and adaptation.","PeriodicalId":7925,"journal":{"name":"Annual Review of Condensed Matter Physics","volume":"31 1","pages":""},"PeriodicalIF":22.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142643074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}