Explanipedia

Defect Bootstrap: Tight Ground State Bounds in Spontaneous Symmetry Breaking Phases Open

Michael G. Scheer, Nisarg Chadha, Da-Chuan Lu, Eslam Khalaf · 2025

The recent development of bootstrap methods based on semidefinite relaxations of positivity constraints has enabled rigorous two-sided bounds on local observables directly in the thermodynamic limit. However, these bounds inevitably become…

Exact models of chiral flat-band superconductors Open

Zhaoyu Han, Jonah Herzog-Arbeitman, Qiang Gao, Eslam Khalaf · 2025

Recent experiments have reported the surprising observation of superconductivity in flavor polarized, nearly flat bands (FBs) of rhombohedral graphene. Motivated by these findings, we introduce a class of models for single-flavor FBs with …

Anyon dispersion from non-uniform magnetic field on the sphere Open

Mina-Lou Schleith, Tomohiro Soejima, Eslam Khalaf · 2025

The discovery of fractional quantum anomalous Hall states in moiré systems has raised the interesting possibility of realizing phases of itenerant anyons. Anyon dispersion is only possible in the absence of continuous magnetic translation …

Nonlocal Moments and Mott Semimetal in the Chern Bands of Twisted Bilayer Graphene Open

Patrick J. Ledwith, Junkai Dong, Ashvin Vishwanath, Eslam Khalaf · 2025

Twisted bilayer graphene (TBG) has elements in common with two paradigmatic examples of strongly correlated physics: quantum Hall physics and Hubbard physics. On one hand, TBG hosts flat topological Landau-level-like bands which exhibit th…

Anyon superconductivity and plateau transitions in doped fractional quantum anomalous Hall insulators Open

P. A. Nosov, Zhaoyu Han, Eslam Khalaf · 2025

Recent experiments reported evidence of superconductivity and re-entrant integer quantum anomalous Hall (RIQAH) insulator upon doping the $ν_e = 2/3$ fractional quantum anomalous Hall states (FQAH) in twisted MoTe${}_2$, separated by narro…

Angular Interplay of Nematicity, Superconductivity, and Strange Metallicity in a Moiré Flat Band Open

Naiyuan James Zhang, P. A. Nosov, Ophelia Evelyn Sommer, Yibang Wang, Kenji Watanabe , et al. · 2025

Superconductivity in strongly correlated electron systems frequently exhibits broken rotational symmetry, raising fundamental questions about the underlying order parameter symmetry. In this work, we demonstrate that electronic nematicity-…

Higher Vortexability: Zero-Field Realization of Higher Landau Levels Open

Manato Fujimoto, Daniel E. Parker, Junkai Dong, Eslam Khalaf, Ashvin Vishwanath , et al. · 2025

The rise of moiré materials has led to experimental realizations of integer and fractional Chern insulators in small or vanishing magnetic fields. At the same time, a set of minimal conditions sufficient to guarantee an Abelian fractional …

Theory of magnetoroton bands in moiré materials Open

Bishoy M. Kousa, Nicolás Morales-Durán, Tobias Wolf, Eslam Khalaf, A. H. MacDonald · 2025

The recent realizations of the Hofstadter butterfly and fractional Chern insulators in moiré materials have introduced a new ingredient, a periodic lattice potential, to the study of quantum Hall phases. While the fractionalized states in …

Robust Super-Moiré in Large Angle Single-Twist Bilayers Open

Yanxing Li, Chuqiao Shi, Fan Zhang, Xiaohui Liu, Xue Yuan , et al. · 2025

Forming long wavelength moiré superlattices (MSL) at small-angle twist van der Waals (vdW) bilayers has been a key approach to creating moiré flat bands. The small-angle twist, however, leads to strong lattice reconstruction, causing domai…

Bootstrapping the Quantum Hall problem Open

Qiang Gao, Ryan A. Lanzetta, Patrick J. Ledwith, Jie Wang, Eslam Khalaf · 2024

The bootstrap method aims to solve problems by imposing constraints on the space of physical observables, which often follow from physical assumptions such as positivity and symmetry. Here, we employ a bootstrap approach to study interacti…

National study comparing psychiatric presentations among migrants and citizens in Qatar Open

Javed Latoo, Ovais Wadoo, Yousaf Iqbal, Faisal Khan, Khizara Amin , et al. · 2024

Arab countries host 10 % of the global migrant population, yet research on the mental health of migrant workers within this region is notably lacking. Addressing this gap, our study marks the inaugural nationwide investigation into psychia…

Nonlocal Moments in the Chern Bands of Twisted Bilayer Graphene Open

Patrick J. Ledwith, Junkai Dong, Ashvin Vishwanath, Eslam Khalaf · 2024

Twisted bilayer graphene (TBG) has elements in common with two paradigmatic examples of strongly correlated physics: quantum Hall physics and Hubbard physics. On one hand, TBG hosts flat topological Landau-level-like bands which exhibits q…

Field-Tunable Valley Coupling and Localization in a Dodecagonal Semiconductor Quasicrystal Open

Zhida Liu, Qiang Gao, Yanxing Li, Xiaohui Liu, Fan Zhang , et al. · 2024

Quasicrystals are characterized by atomic arrangements possessing long-range order without periodicity. Van der Waals (vdW) bilayers provide a unique opportunity to controllably vary atomic alignment between two layers from a periodic moir…

Adiabatic approximation and Aharonov-Casher bands in twisted homobilayer transition metal dichalcogenides Open

Jingtian Shi, Nicolás Morales-Durán, Eslam Khalaf, A. H. MacDonald · 2024

Topological flat moir\\'e bands with nearly ideal quantum geometry have been\nidentified in homobilayer transition metal dichalcogenide moir\\'e\nsuperlattices, and are thought to be crucial for understanding the fractional\nChern insulati…

Constraints on real space representations of Chern bands Open

Qiao Yu Li, Junkai Dong, Patrick J. Ledwith, Eslam Khalaf · 2024

A Chern band is characterized by a Wannier obstruction indicating the absence of a basis of complete, orthogonal, and exponentially-localized states. Here, we study the properties of real space bases of a Chern band obtained by relaxing ei…

Strong interactions and isospin symmetry breaking in a supermoiré lattice Open

Yonglong Xie, Andrew T. Pierce, Jeong Min Park, Daniel E. Parker, Jie Wang , et al. · 2024

In multilayer moiré heterostructures, the interference of multiple twist angles ubiquitously leads to tunable ultra-long-wavelength patterns known as supermoiré lattices. However, their impact on the system's many-body electronic phase dia…

Higher vortexability: zero field realization of higher Landau levels Open

Manato Fujimoto, Daniel E. Parker, Junkai Dong, Eslam Khalaf, Ashvin Vishwanath , et al. · 2024

The rise of moiré materials has led to experimental realizations of integer and fractional Chern insulators in small or vanishing magnetic fields. At the same time, a set of minimal conditions sufficient to guarantee a Abelian fractional s…

Tuning commensurability in twisted van der Waals bilayers Open

Yanxing Li, Fan Zhang, Viet-Anh Ha, Yu‐Chuan Lin, Chengye Dong , et al. · 2024

Moiré superlattices based on van der Waals bilayers^1-4 created at small twist angles lead to a long wavelength pattern with approximate translational symmetry. At large twist angles (θ_t), moiré patterns are, in genera…

Many-body ground states from decomposition of ideal higher Chern bands: Applications to chirally twisted graphene multilayers Open

Junkai Dong, Patrick J. Ledwith, Eslam Khalaf, Jong Yeon Lee, Ashvin Vishwanath · 2023

Motivated by the higher Chern bands of twisted graphene multilayers, we consider flat bands with arbitrary Chern number C with ideal quantum geometry. While C>1 bands differ from Landau levels, we show that these bands host exact fractiona…

Untwisting moiré physics: Almost ideal bands and fractional Chern insulators in periodically strained monolayer graphene Open

Qiang Gao, Junkai Dong, Patrick J. Ledwith, Daniel Parker, Eslam Khalaf · 2022

Moiré systems have emerged in recent years as a rich platform to study strong correlations. Here, we will discuss a simple, experimentally feasible setup based on periodically strained graphene that reproduces several key aspects of twiste…

Exact Many-Body Ground States from Decomposition of Ideal Higher Chern Bands: Applications to Chirally Twisted Graphene Multilayers Open

Junkai Dong, Patrick J. Ledwith, Eslam Khalaf, Jong Yeon Lee, Ashvin Vishwanath · 2022

Motivated by the higher Chern bands of twisted graphene multilayers, we consider flat bands with arbitrary Chern number $C$ with ideal quantum geometry. While $C>1$ bands differ from Landau levels, we show that these bands host exact fract…

Baby skyrmions in Chern ferromagnets and topological mechanism for spin-polaron formation in twisted bilayer graphene Open

Eslam Khalaf, Ashvin Vishwanath · 2022

Emergence of correlations in alternating twist quadrilayer graphene Open

G. William Burg, Eslam Khalaf, Kenji Watanabe, Takashi Taniguchi, Emanuel Tutuc · 2022

Symmetry constraints on superconductivity in twisted bilayer graphene: Fractional vortices, condensates, or nonunitary pairing Open

Eslam Khalaf, Patrick J. Ledwith, Ashvin Vishwanath · 2022

When two graphene sheets are twisted relative to each other by a small angle,\nenhanced correlations lead to superconductivity whose origin remains under\ndebate. Here, we derive some general constraints on superconductivity in\ntwisted bi…

Symmetry Origin of Lattice Vibration Modes in Twisted Multilayer Graphene: Phasons vs Moiré Phonons Open

Qiang Gao, Eslam Khalaf · 2022

Lattice dynamics play a crucial role in the physics of Moiré systems. In twisted bilayer graphene (TBG), it was shown that, in addition to the graphene phonons, there is another set of gapless excitations termed Moiré Phonons [Phys. Rev. B…

Dirac cone spectroscopy of strongly correlated phases in twisted trilayer graphene Open

Shen Cheng, Patrick J. Ledwith, Kenji Watanabe, Takashi Taniguchi, Eslam Khalaf , et al. · 2022

Mirror-symmetric magic-angle twisted trilayer graphene (MATTG) hosts flat electronic bands close to zero energy, and has been recently shown to exhibit abundant correlated quantum phases with flexible electrical tunability.1–3 However stud…

Family of Ideal Chern Flatbands with Arbitrary Chern Number in Chiral Twisted Graphene Multilayers Open

Patrick J. Ledwith, Ashvin Vishwanath, Eslam Khalaf · 2022

We consider a family of twisted graphene multilayers consisting of n-untwisted chirally stacked layers, e.g., AB, ABC, etc, with a single twist on top of m-untwisted chirally stacked layers. Upon neglecting both trigonal warping terms for …

Dirac cone spectroscopy of strongly correlated phases in twisted trilayer graphene Open

Shen Cheng, Patrick J. Ledwith, Kenji Watanabe, Takashi Taniguchi, Eslam Khalaf , et al. · 2022

Mirror-symmetric magic-angle twisted trilayer graphene (MATTG) hosts flat electronic bands close to zero energy, and has been recently shown to exhibit abundant correlated quantum phases with flexible electrical tunability. However studyin…

The Impact of COVID-19 Pandemic on Individuals With Pre-existing Obsessive-Compulsive Disorder in the State of Qatar: An Exploratory Cross-Sectional Study Open

Maryam Hussain Siddiqui, Ovais Wadoo, James Currie, Majid Alabdulla, Areej Al Siaghy , et al. · 2022

Background Published evidence about the impact of the COVID-19 pandemic on Obsessive-Compulsive Disorder (OCD) is conflicting. Most studies suggest an increase in the severity of OCD in people with pre-existing OCD, whereas some do not. Ai…

Fermionic Monte Carlo Study of a Realistic Model of Twisted Bilayer Graphene Open

Johannes S. Hofmann, Eslam Khalaf, Ashvin Vishwanath, Erez Berg, Jong Yeon Lee · 2022

The rich phenomenology of twisted bilayer graphene (TBG) near the magic angle is believed to arise from electron correlations in topological flat bands. An unbiased approach to this problem is highly desirable, but also particularly challe…

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