Keyword

condensed matter

4 papers tagged “condensed matter”

PhysicsNature · Apr 2018 Open access

Unconventional superconductivity in magic-angle graphene superlattices

Yuan Cao, Valla Fatemi, Shiang Fang, Kenji Watanabe, Takashi Taniguchi, Efthimios Kaxiras, et al.

The authors stacked two graphene sheets twisted by a 'magic' angle of about 1.1 degrees, producing flat electronic bands in the resulting moire superlattice. Upon electrostatically doping near half-filling of these flat bands, they observed superconductivity with critical temperatures up to about 1.7 K. The behaviour resembles that of unconventional, strongly correlated superconductors such as the cuprates, demonstrating a tunable platform for studying correlated electron physics.

twisted bilayer graphene superconductivity magic angle moire superlattice

PhysicsNature · Jul 2017 Open access

Topological quantum chemistry

Barry Bradlyn, L. Elcoro, Jennifer Cano, M. G. Vergniory, Zhijun Wang, C. Felser, et al.

The authors develop a complete framework linking the symmetry properties of electronic bands to topological character, merging group theory of crystallographic space groups with band structure analysis. By cataloguing how atomic orbitals at Wannier centers transform under crystal symmetries, they identify which band structures are topologically trivial (atomic limit) versus topologically nontrivial. This enabled systematic, predictive identification of topological materials from symmetry data alone.

topological insulators band theory condensed matter symmetry

PhysicsScience · Jul 2017 Open access

Quantized electric multipole insulators

Wladimir A. Benalcazar, B. Andrei Bernevig and Taylor L. Hughes

The paper generalizes the theory of electric polarization to higher electric multipole moments (quadrupole and octupole), showing these can be topologically quantized bulk observables in crystalline insulators. It introduces tight-binding models whose gapped edges are themselves lower-dimensional topological phases, producing protected, fractionally charged corner states. This work effectively launched the field of higher-order topological insulators.

higher-order topological insulators multipole moments corner states condensed matter

ChemistryScience · Oct 2004 Open access

Electric Field Effect in Atomically Thin Carbon Films

K. S. Novoselov, A. K. Geim and S. V. Morozov

This paper demonstrated that atomically thin, monocrystalline graphitic films—down to a single atomic layer (graphene)—can be isolated, are stable under ambient conditions, and are of high crystalline and electronic quality. The authors showed that these films behave as a two-dimensional semimetal with a small overlap between valence and conduction bands and exhibit a strong ambipolar electric field effect, with charge-carrier concentrations up to 10¹³ cm⁻² and room-temperature mobilities of about 10,000 cm²/V·s tunable by a gate voltage. The work launched the experimental field of two-dimensional materials and underpinned the 2010 Nobel Prize in Physics awarded to Geim and Novoselov.

graphene two-dimensional materials field effect carbon