About

Ian Abel is an Associate Research Scientist at the Institute for Research in Electronics & Applied Physics at the University of Maryland. His research focuses on electronics, applied physics, and related fields. His work involves contributing to the advancement of research in electronics and applied physics, supporting the university's broader scientific and engineering initiatives.

Research topics

• Condensed matter physics
• Materials science
• Physics
• Optoelectronics
• Atomic physics

Selected publications

• Excitons beyond the effective mass approximation: application to biased bilayer graphene

  Bulletin of the American Physical Society · 2019-03-05

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• Surface phases on Te (0001) single crystal by low temperature STM

  Bulletin of the American Physical Society · 2019-03-05

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• Excitons without effective mass: Biased bilayer graphene

  Physical review. B./Physical review. B · 2019-01-22 · 12 citations

  articleOpen accessSenior author

  Understanding the dynamics of excitons in two-dimensional semiconductors requires a theory that incorporates the essential physics distinct from their three-dimensional counterparts. In addition to the modified dielectric environment, single-particle states with strongly nonparabolic dispersion appear in many two-dimensional band structures, so that ``effective mass'' is ill-defined. Focusing on electrostatically biased bilayer graphene as an example where quartic (and higher) dispersion terms are necessary, we present a semianalytic theory used to investigate the properties of ground and excited excitonic states. This includes determination of relative oscillator strengths and magnetic moments (valley $g$-factors) which can be directly compared to recent experimental measurements.

  PublisherOA PDFDOI

• Spin Transport in Si and Ge

  2019-05-20

  book-chapter1st authorCorresponding

  This chapter reviews some fundamental properties of tunneling spin-current, spin-transport of holes and spin-transfer of angular momenta in the valence band of magnetic III–V tunneling heterojunctions involving the ferromagnetic semiconductor (Ga,Mn)As. It discusses the modeling via advanced k·p kinetic exchange approach, the angular momentum transport in the valence band of semiconductors heterostructures. The chapter describes spin transfer torque experiments which have been demonstrated in the systems accounting for the conservation of the angular momenta of holes carried by the current for perpendicular-to-plane and in-plane current injection. It explores the skew tunneling and explains in detail the anomalous tunneling Hall Effect. The chapter demonstrates results of transport asymmetry implemented with advanced 30-band k·p methods adapted to the tunneling transport and using relevant wave function and wave current matching conditions that one compares to more standard k·p codes with excellent agreement. The general description of spin-polarized tunnel transport, including is fully described using standard k·p theory and Laudauer Buttiker formalism.

  PublisherDOI

• Intrinsic two-dimensional states on the pristine surface of tellurium

  Physical review. B./Physical review. B · 2018-05-07 · 12 citations

  articleOpen accessSenior author

  Atomic chains configured in a helical geometry have fascinating properties, including phases hosting localized bound states in their electronic structure. We show how the zero-dimensional state---bound to the edge of a single one-dimensional helical chain of tellurium atoms---evolves into two-dimensional bands on the $c$-axis surface of the three-dimensional trigonal bulk. We give an effective Hamiltonian description of its dispersion in $k$ space by exploiting confinement to a virtual bilayer, and elaborate on the diminished role of spin-orbit coupling. These intrinsic gap-penetrating surface bands were neglected in the interpretation of seminal experiments, where two-dimensional transport was otherwise attributed to extrinsic accumulation layers.

  PublisherOA PDFDOI

• Illuminating "spin-polarized" Bloch wave-function projection from degenerate bands in decomposable centrosymmetric lattices

  Physical review. B./Physical review. B · 2018-03-29 · 11 citations

  articleOpen accessSenior author

  As previously explored with sophisticated computational methods, projecting out incomplete components of Bloch wave functions yields `states' that appear to be `spin polarized'. Here, the consequences and physical relevance of this so-called hidden spin polarization obtained by wave-function truncation is revealed by inspection of analytically solvable models. Importantly, the limitations and shortcomings of this electronic structure decomposition are illuminated using arguments focused on operator commutativity and broken gauge freedom in degenerate wave-function projection. Moreover, it is shown how surface-sensitive measurements using experimental techniques, such as ARPES, are inevitably convoluted by intrinsic spin splitting of the band structure due to broken inversion symmetry at the surface.

  PublisherOA PDFDOI

• Origins of open circuit voltage hysteresis driven by transverse charge current in ferromagnet/normal metal structures

  Bulletin of the American Physical Society · 2017-03-16

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• Symmetry analysis of 2D four-six-enes (group-IV metal monochalcogenides): electrons, holes, spin and excitons

  Bulletin of the American Physical Society · 2017-03-14

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• Robust zero-energy bound states in a helical lattice

  Physical review. B./Physical review. B · 2017-09-27 · 9 citations

  articleOpen accessSenior author

  Atomic-scale helices exist as motifs for several material lattices. We examine a tight-binding model for a single one-dimensional monatomic chain with a $p$-orbital basis coiled into a helix. A topologically nontrivial phase emerging from this model supports a chiral symmetry-protected zero-energy mode localized to a boundary, always embedded within a continuum band, regardless of termination site. We identify a topological invariant for this phase that is related to the number of zero energy end modes by means of the bulk-boundary correspondence, and give strict conditions for the existence of the bound state. An additional class of gapped edge modes in the model spectrum has practical consequences for surface states in, e.g., trigonal tellurium and selenium and other van der Waals-bonded one-dimensional semiconductors.

  PublisherOA PDFDOI

• Spin-orbit interaction in monolayer (group-III) metal-monochalcogenides

  Bulletin of the American Physical Society · 2016-03-15

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Recent grants

• Scalable Digital Spin Logic Devices

  NSF · $360k · 2012–2017

• CAREER: Silicon Spintronics

  NSF · $400k · 2008–2014

• Harmonic detection of the Majorana fermion in narrow bandgap InAsSb

  NSF · $120k · 2014–2016

Frequent coauthors

• Biqin Huang

  34 shared

• V. Narayanamurti

  Harvard University Press

  30 shared

• Jing Li

  Central China Normal University

  29 shared

• Pengke Li

  University of Rochester

  24 shared

• Kasey J. Russell

  Draper Laboratory

  21 shared

• A. C. Gossard

  University of California, Santa Barbara

  15 shared

• M. Hanson

  Cardiff University

  15 shared

• Hyuk‐Jae Jang

  Kyoto University Institute for Chemical Research

  14 shared

Labs

• Ian Appelbaum LabPI

Awards & honors

• Glenn L. Martin Medal
• Greenaugh Award
• Innovation Hall of Fame
• 125th Anniversary Medal
• Early Career Distinguished Alumni Society