Measurements of Interaction-Driven States in Monolayer and Bilayer Graphene

In materials systems with flat energy bands and limited disorder, interactions among electrons dominate and can dramatically alter physical behavior. Traditionally, two-dimensional electron gases (2DEGs) have offered excellent platforms to study these effects because the kinetic energy of the electrons is effectively quenched by a perpendicular magnetic field. The recent discovery of graphene, a two-dimensional form of carbon, has opened the door for further exploration into many-body phenomena. Graphene, unlike conventional 2DEGs, has fourfold degenerate electronic states due to its spin and valley degrees of freedom. This thesis describes several experiments that show how these underlying symmetries combine with electron-electron interactions to produce novel and tunable correlated electronic phases of matter.Physic

Local Compressibility Measurements of Correlated States in Suspended Bilayer Graphene

Bilayer graphene has attracted considerable interest due to the important role played by many-body effects, particularly at low energies. Here we report local compressibility measurements of a suspended graphene bilayer. We find that the energy gaps at filling factors v = 4 do not vanish at low fields, but instead merge into an incompressible region near the charge neutrality point at zero electric and magnetic field. These results indicate the existence of a zero-field ordered state and are consistent with the formation of either an anomalous quantum Hall state or a nematic phase with broken rotational symmetry. At higher fields, we measure the intrinsic energy gaps of broken-symmetry states at v = 0, +/-1 and +/-2, and find that they scale linearly with magnetic field, yet another manifestation of the strong Coulomb interactions in bilayer graphene.Physic

Fractional Quantum Hall Phase Transitions and Four-Flux States in Graphene

Graphene and its multilayers have attracted considerable interest because their fourfold spin and valley degeneracy enables a rich variety of broken-symmetry states arising from electron-electron interactions, and raises the prospect of controlled phase transitions among them. Here we report local electronic compressibility measurements of ultraclean suspended graphene that reveal a multitude of fractional quantum Hall states surrounding filling factors $\nu =−1/2$ and $−1/4$. Several of these states exhibit phase transitions that indicate abrupt changes in the underlying order, and we observe many additional oscillations in compressibility as $\nu$ approaches $−1/2$, suggesting further changes in spin and/or valley polarization. We use a simple model based on crossing Landau levels of composite fermions with different internal degrees of freedom to explain many qualitative features of the experimental data. Our results add to the diverse array of many-body states observed in graphene and demonstrate substantial control over their order parameters.Engineering and Applied SciencesPhysic

Electron-hole asymmetric integer and fractional quantum Hall effect in bilayer graphene

The nature of fractional quantum Hall (FQH) states is determined by the interplay between the Coulomb interaction and the symmetries of the system. The unique combination of spin, valley, and orbital degeneracies in bilayer graphene is predicted to produce novel and tunable FQH ground states. Here we present local electronic compressibility measurements of the FQH effect in the lowest Landau level of bilayer graphene. We observe incompressible FQH states at filling factors $\nu = 2p + 2/3$ with hints of additional states appearing at $\nu = 2p + 3/5$, where p = -2,-1, 0, and 1. This sequence of states breaks particle-hole symmetry and instead obeys a $\nu \rightarrow \nu + 2$ symmetry, which highlights the importance of the orbital degeneracy for many-body states in bilayer graphene.Engineering and Applied SciencesPhysic

Changing Culture : The Contribution of European Immigrants to New York City Literature, 1870–1940

This comprehensive look at the New York literature of European immigrants invites us to rethink in aesthetic terms the interaction between the psychic and the socio-historical. A closer look at the literary dimension of the Irish, German, Scandinavian and Dutch, Italian, Jewish, Polish, Greek, and other components of New York raises the question of the specificity whereby immigrant authors, or second-generation authors with a strong, obvious immigrant background, related to, and portrayed a city, and a city like no other such as New York. Mass immigration meant the almost perfect concentration in the New York of that period of the three classical dramatic unities of time, place and action, thus giving evidence to an epochal change that was at the same time external and internal, socio-political and existential, and whose effects are palpably present in the immigrants\u2019 literature. The massive global inflows from Castle Garden and Ellis Island happened because, and coincided with, a tumultuous industrial, economic and capitalist thrust, and caused a gigantic urban growth. To be sure, this was a phenomenon of obviously global dimensions, which concurred and vied with the aggressive nationalistic mind-set of the time and became an active element of a push and pull dynamic. Indeed, \u2018in a multitude of ways each immigrant culture articulated group identity as national identity\u2019

New and old Amsterdam in Twenty-First Century fiction

This chapter examines the evocation of New Amsterdam within contemporary novels of New York. You would think that, considering its humble, yet extraordinary beginnings as New Amsterdam, New York’s earliest history as a multicultural, multilingual Dutch settlement might have generated its own literature. However, this origin point is largely absent within American literary history. By assessing how New York’s Dutch origins have been featured in contemporary literature, this chapter examines Joseph O’Neill’s Netherland, Teju Cole’s Open City and Donna Tartt’s The Goldfinch. These novels are examined for how New Amsterdam is set as the scene for New York’s present and its future