Electrifying Discoveries

A Look Back at the APS March Meeting 2012

The American Physical Society's March Meeting is where the future of physics is written, one presentation at a time.

Introduction: A Confluence of Physics Minds

Every year, the American Physical Society's March Meeting serves as a vibrant nexus for the global physics community. It is where groundbreaking research is unveiled, collaborations are born, and the future trajectory of the field is often set. The 2 2012 meeting, held from February 27 to March 2 in Boston, Massachusetts, was a quintessential example of this dynamic exchange. It brought together thousands of physicists to share discoveries across an astonishingly broad spectrum of topics, from the intricacies of the quantum world to the practical challenges of energy storage and medical technology.

The significance of this meeting lay not only in the presentation of individual studies but in the collective mapping of physics' most exciting frontiers. Attendees witnessed the early stages of research that would go on to shape new technologies and deepen our fundamental understanding of the universe. This article revisits the 2012 meeting, highlighting the key themes and diving deep into a pivotal experiment that showcased the power of innovative physics to reveal new truths about well-studied materials.

Meeting Facts
  • Date: Feb 27 - Mar 2, 2012
  • Location: Boston, Massachusetts
  • Attendees: Thousands of physicists
  • Scope: Broad spectrum of physics topics
Key Research Areas
Quantum Entanglement Active Matter Energy Solutions Materials Science Graphene Research

The Main Stage: Cutting-Edge Physics in Focus

The 2012 APS March Meeting was notable for its blend of fundamental inquiry and applied research. The sessions covered a wide array of subjects, reflecting the increasingly interdisciplinary nature of the field.

Quantum Entanglement & Information

A significant portion of the meeting was dedicated to exploring the strange and powerful phenomena of quantum mechanics. Session W30, focused on "Quantum Entanglement," featured talks on using entanglement as a resource for complex computations and communications 4 .

Researchers presented new methods for characterizing the channel capacity of high-dimensional entangled states, achieving a remarkable channel capacity of over 7 bits per photon 4 .

Active Matter & Biological Physics

Another fascinating area was the study of "active matter"—systems composed of individual units that consume energy to generate motion. In an invited session, Frank Jülicher from the Max Planck Institute discussed how active processes in biological matter, like the force generation by molecular motors in cell structures, create spontaneous mechanical stresses and flows 5 .

This research is crucial for understanding fundamental cellular processes, including cell division and locomotion.

Energy Solutions & Materials Science

Addressing pressing global needs, several sessions were devoted to energy research. Scientists presented work on new materials for methane storage, exploring how densified activated carbon monoliths could optimize fuel tanks for natural gas vehicles 9 .

Meanwhile, other researchers discussed converting solar energy into fuels through advanced interface catalysis, aiming to harness sunlight as efficiently as plants do 1 .

Research Focus Areas at APS 2012

An In-Depth Look: Probing the Secrets of Pristine Bilayer Graphene

To understand how progress is made at a meeting like this, let's examine one experiment in detail. A team from Columbia University presented a sophisticated study on the electronic structure of free-standing bilayer graphene, a material with immense promise for future electronics 7 .

The Goal and The Challenge

The researchers' goal was to measure the fundamental electronic properties of bilayer graphene without the confounding influence of a substrate. When graphene is placed on a surface like silicon dioxide, the substrate's unwanted doping and microscopic roughness can mask the material's intrinsic behavior. By studying graphene suspended over tiny wells, the team aimed to access its true "pristine" properties 7 .

Methodology: A Step-by-Step Probe

The experiment required a combination of advanced material preparation and high-precision measurement techniques.

Sample Preparation

The team began by mechanically exfoliating, or "peeling," high-quality graphene crystals onto a silicon dioxide substrate etched with an array of 5-micrometer wells. This process resulted in graphene flakes draped over the wells, creating free-standing sections.

Identification and Targeting

Using a spectromicroscope at the Elettra synchrotron in Italy, they took spatially-resolved photoemission images to identify and pinpoint specific regions of interest—namely, monolayer and bilayer graphene suspended over the wells.

Data Acquisition

With the sample cooled to 110 Kelvin to reduce thermal noise, they focused a beam of 27 eV photons to a spot smaller than one micrometer on the suspended bilayer graphene. The ARPES instrument then measured the energy and angle of electrons ejected from the sample.

Data Analysis

The raw ARPES data was processed through coordinate transforms and curve-fitting algorithms. The researchers fitted the energy distribution curves to a theoretical model to extract precise values for key physical parameters.

Research Tools and Materials

Research Tool/Material Function in the Experiment
Mechanically Exfoliated Graphene Provided high-quality, crystalline samples for study.
Silicon Substrate with 5μm Wells Created a support structure allowing sections of graphene to be suspended freely.
Spectromicroscopy (SPELEEM) Combined microscopy and spectroscopy, allowing the team to visually locate the graphene layers and then perform spectroscopic analysis on them with a high spatial resolution (∼40 nm).
Synchrotron Light Source (Elettra) Generated high-intensity, monochromatic light (27 eV photons) to excite electrons in the graphene samples for ARPES measurements.
Angle-Resolved Photoemission Spectroscopy (ARPES) The core technique used to directly "map" the relationship between the energy and momentum of electrons in the graphene, revealing its band structure.

Results and Analysis: A Clearer Picture Emerges

The experiment was a success. The ARPES data from the suspended graphene showed significantly sharper spectral peaks than measurements from substrate-supported graphene, confirming that removing the substrate revealed the material's intrinsic electronic behavior 7 .

The team was able to precisely measure three fundamental properties of bilayer graphene:

Parameter Symbol Value from Suspended Graphene (110K) 7 Comparison: IR Study on Doped Graphene 7
Fermi Velocity VF (1.003 ± 0.013) × 106 m/s ~1.1 × 106 m/s
Interlayer Coupling γ1 0.611 ± 0.007 eV 0.378 ± 0.005 eV
Interlayer Asymmetry Δ 56.2 ± 9.4 meV Not detected

The analysis confirmed that the electronic structure closely followed theoretical predictions for pristine bilayer graphene. A particularly important finding was the presence of a small but measurable band asymmetry (Δ), which was detected with much greater clarity in the suspended sample 7 .

Key Finding

The measured Fermi velocity and interlayer coupling were in reasonable agreement with other high-quality samples, validating the experimental approach.

This work provided a crucial benchmark for the physics of bilayer graphene, offering a clean reference point against which the effects of different substrates and external electric fields could be more accurately measured in the future.

Lasting Impact and Conclusion

The 2012 APS March Meeting was more than just a conference; it was a snapshot of a field in rapid motion. The research presented, from the manipulation of Majorana fermions for quantum computing to the development of nanostructured anti-icing surfaces, demonstrated physics' unique role in both satisfying human curiosity and solving tangible problems 1 .

The study on suspended bilayer graphene, detailed here, is a prime example of the foundational work that enables future technological leaps. By meticulously characterizing the material in its pure form, physicists laid the essential groundwork for designing the next generation of electronic devices.

The enduring legacy of such meetings is the community and the conversation they foster. They are where a result on quantum entanglement inspires a new calculation, where a technique for studying active matter is adapted for medical research, and where a young researcher is inspired to tackle the next great challenge.

The 2012 meeting, with its diverse and dynamic program, perfectly captured this spirit of collaborative discovery, pushing the entire field of physics forward.

Key Contributions
  • Advanced quantum entanglement research
  • Breakthroughs in active matter physics
  • Innovations in energy storage materials
  • Pristine graphene characterization
  • Interdisciplinary collaborations

References