Publications by Yifei Guan | EPFL Graph Search

Electronic transport in graphene with out-of-plane disorder

Real-world samples of graphene often exhibit various types of out-of-plane disorder-ripples, wrinkles and folds-introduced at the stage of growth and transfer processes. These complex out-of-plane defects resulting from the interplay between self-adhesion ...

Nature Portfolio2024

Observation of Kekulé vortices around hydrogen adatoms in graphene

Oleg Yazyev, Yifei Guan

Fractional charges are one of the wonders of the fractional quantum Hall effect. Such objects are also anticipated in two-dimensional hexagonal lattices under time reversal symmetry-emerging as bound states of a rotating bond texture called a Kekule vortex ...

Nature Portfolio2024

Strongly correlated Hofstadter subbands in minimally twisted bilayer graphene

Oleg Yazyev, Yifei Guan, Mitali Banerjee

Moiré superlattice in twisted bilayer graphene has been proven to be a versatile platform for exploring exotic quantum phases. Extensive investigations have been invoked focusing on the zero-magnetic-field phase diagram at the magic twist angle around $\th ...

American Physiological Society2024

Topological Effects in Carbon-based Two-dimensional Nanostructures

Yifei Guan

Recent advances on low-dimensional and topological materials has greatly inspired the research in condensed matter physics. This thesis is devoted to the computational and theoretical study of topological effects in two-dimensional materials, especially na ...

EPFL2023

Engineering SYK Interactions in Disordered Graphene Flakes under Realistic Experimental Conditions

Oleg Yazyev, Yifei Guan, Marta Agnieszka Brzezinska

We model interactions following the Sachdev-Ye-Kitaev (SYK) framework in disordered graphene flakes up to 300 000 atoms in size (-100 nm in diameter) subjected to an out-of-plane magnetic field B of 5-20 Tesla within the tight-binding formalism. We investi ...

AMER PHYSICAL SOC2023

Unconventional Flat Chern Bands and 2e Charges in Skyrmionic Moire Superlattices

Oleg Yazyev, Yifei Guan

The interplay of topological characteristics in real space and reciprocal space can lead to the emergence of unconventional topological phases. In this Letter, we implement a novel mechanism for generating higher-Chern flat bands on the basis of twisted bi ...

AMER CHEMICAL SOC2023

Symmetry and topology of hyperbolic Haldane models

Yifei Guan

Particles hopping on a two-dimensional hyperbolic lattice feature unconventional energy spectra and wave functions that provide a largely uncharted platform for topological phases of matter beyond the Euclidean paradigm. Using real-space topological marker ...

Amer Physical Soc2023

Landau levels of the Euler class topology

Oleg Yazyev, Yifei Guan

Two-dimensional systems with C2T (PT) symmetry exhibit the Euler class topology E is an element of Z in each two-band subspace realizing a fragile topology beyond the symmetry indicators. By systematically studying the energy levels of Euler insulating pha ...

AMER PHYSICAL SOC2022

Reentrant magic-angle phenomena in twisted bilayer graphene in integer magnetic fluxes

Oleg Yazyev, Yifei Guan

In this Letter we address the reentrance of magic-angle phenomena (band flatness and quantum-geometric transport) in twisted bilayer graphene (TBG) subjected to strong magnetic fluxes +/-(1)0, +/- 200, +/- 3(p0 ... ((D0 = h/e is the flux quantum per moire ...

AMER PHYSICAL SOC2022

Landau Levels as a Probe for Band Topology in Graphene Moire Superlattices

Oleg Yazyev, Quansheng Wu, Yifei Guan

We propose Landau levels as a probe for the topological character of electronic bands in two-dimensional moire superlattices. We consider two configurations of twisted double bilayer graphene (TDBG) that have very similar band structures, but show differen ...

AMER PHYSICAL SOC2021

Search for CP violation with kinematic asymmetries in the D-0 -> K+K- pi(+)pi(-) decay

Olivier Schneider, Sun Hee Kim, Tagir Aushev, Mingkui Wang, Chao Wang, Kyung Taek Cho, Jun Yong Kim, Mithilesh Nayak, Donghyun Kim, Yifei Guan, Lei Li, Ji Hyun Kim, Yiming Li, Xiao Wang

We search for CP violation in the singly-Cabibbo-suppressed decay D-0 -> K+K-pi(+)pi(-) using data corresponding to an integrated luminosity of 988 fb(-1) collected by the Belle detector at the KEKB e(+)e(-). We measure a set of five kinematically dependen ...

American Physical Society2019

Measurements of isospin asymmetry and difference of direct CP asymmetries in inclusive B -> X-s gamma decays

Olivier Schneider, Sun Hee Kim, Steve Michel Berger, Tagir Aushev, Mingkui Wang, Chao Wang, Yong Chan Choi, Arnaud Michel Gelb, Kyung Taek Cho, Jun Yong Kim, Linlin Cao, Carsten Hao Ye Chong, Tara Nanut, Donghyun Kim, Martin Lubej, Chang-Hyun Park, Yifei Guan, Lei Li, Ji Hyun Kim, Yiming Li

We report measurements of isospin asymmetry Delta(0-) and difference of direct CP asymmetries Delta A(CP) between charged and neutral B -> X-s gamma decays. This analysis is based on the data sample containing 772 x 10(6)B (B) over bar pairs that was colle ...

American Physical Society2019