phenomenon · claim-type · cross-domain-transfer · mechanism · claim-relation · replication-status · limitation — grounded in the full text| phenomenon | massless Dirac fermion transport in graphene— “Our studies of graphene – a single atomic layer of carbon – have revealed a variety of unusual phenomena characteristic of two-dimensional (2D) Dirac fermions.” | |
| claim-type | existence— “Here we report a condensed matter system where electron transport is essentially governed by the Dirac equation and charge carriers mimic relativistic particles with zero mass and an effective “speed of light” c∗ ≈106m/s.” | |
| method — evidence | — “To obtain graphene samples, we used the original procedures described in [1], which involve micromechanical cleavage of graphite followed by identification and selection of monolayers using a combination of optical, scanning-electron and atomic-force microscopies.” | |
| transfer | from quantum electrodynamics / high-energy physics: graphene charge carriers behave as massless Dirac fermions, letting a condensed-matter experiment probe relativistic QED and cosmology-relevant physics— “the subtle and rich physics of quantum electrodynamics” | transfers[0] |
| mechanism | in graphene the honeycomb lattice makes charge carriers behave as massless Dirac fermions obeying the relativistic Dirac equation rather than the Schrodinger equation— “revealed a variety of unusual phenomena characteristic of two-dimensional (2D) Dirac fermions” | mechanisms[0] |
| builds-on | the Dirac equation (relativistic quantum mechanics / particle physics)— “electron transport is essentially governed by the Dirac equation and charge carriers mimic relativistic particles with zero mass and an effective “speed of light” c∗ ≈106m/s” | claim_relations[0] |
| builds-on | Mott's argument on the minimum mean free path in a metal— “Assuming the absence of localization, the observed minimum conductivity can be explained qualitatively by invoking Mott’s argument [21] that mean-free-path l of charge carriers in a metal can never be shorter that their wavelength λF.” | claim_relations[1] |
| builds-on | the Atiyah-Singer index theorem— “The latter can be viewed as a direct consequence of the Atiyah-Singer index theorem that plays an important role in quantum field theory and the theory of superstrings [13,14].” | claim_relations[2] |
| builds-on | Berry's phase— “Note however that from another perspective the phase shift can be viewed as the direct manifestation of Berry’s phase acquired by Dirac fermions moving in magnetic field [15,16].” | claim_relations[3] |
| sense | mass - TWO MASSES, ONE ZERO AND ONE NOT, IN THE SAME PARTICLE: the linear spectrum implies zero rest mass while the cyclotron mass is explicitly not zero, so a tag reading 'mass = 0' and one reading 'mass is not 0' are both correct here and neither is usable without saying which mass— “implies zero rest mass, their cyclotron mass is not zero” | senses[0] |
| sense | the plus-or-minus sign - SPINS IN QED, PSEUDOSPINS IN GRAPHENE: the authors carry a formula across from quantum electrodynamics and then state that the quantity it indexes here has nothing to do with real spin, its origin being the two carbon sublattices— “The latter have nothing to do with the real spin but are “built in” the Dirac-like spectrum of graphene, and their origin can be traced to the presence of two carbon sublattices” | senses[1] |
| sense | Dirac fermion - BY MIMICRY, NOT BY IDENTITY: the charge carriers are said to MIMIC relativistic particles with zero mass, under a Dirac equation borrowed from relativistic physics, with an effective speed of light the paper itself puts in scare quotes— “Here we report a condensed matter system where electron transport is essentially governed… | senses[2] |
| control | the carrier density measured from the Hall coefficient compared against the value calculated from the device geometry as a parallel-plate capacitor — held — rules out an experimental artefact in either route - a measured 7.3e10 and a calculated 7.2e10 cm-2/V have no common failure mode, so their agreement is not an assumption either one makes | controls[0] |
| edge | rest mass —distinct-from→ cyclotron mass Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concept_edges[0] |
| evidence status note | concept — THE TERM IS NOT IN THE QUOTE - the quote's 'The latter' are the pseudospins named in the sentence just before it ('in the case of graphene it refers to “pseudospins”'). That sentence is not quoted because a displaced formula runs through it. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[6] |
| outcome (stated by the tagger, no quotation) | control — held | controls[0] |
| for which use | limitation — the mobility figures as a property of the material: they were PROBABLY STILL LIMITED BY DEFECTS IN PA[rent graphite], so they bound the sample rather than the substance Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[0] |
| for which use | limitation — the minimum-conductivity result against theory: THERE IS A BROAD THEORETICAL CONSENSUS THAT A 2D GAS OF DIRAC FERMIONS SHOULD EXHIBIT A MINIMUM CONDUCTIVITY OF ABOUT e2/h ... AND MOST THEORIES SUGGEST A VALUE that the measurement does not match Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[1] |
| for which use | limitation — the massless Dirac description used here: the authors state that in two-layer graphene the fermions exhibit a finite mass Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[2] |
| for which use | limitation — the account given here of the minimum conductivity: it is explained qualitatively, assuming the absence of localization, by invoking Mott's argument that the mean free path can never be shorter than the carrier wavelength Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[3] |
| for which use | limitation — the agreement between this measurement and theory: the half-integer QHE was suggested by two theory groups stimulated by the authors' earlier work on thin graphite films but unaware of the present experiment Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[4] |
| replication | untested | |
| limitation | Carrier mobility in the devices is probably still limited by defects inherited from the parent graphite, so the measured mobility is not intrinsic. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[0] |
| limitation | The measured minimum conductivity disagrees with the value most existing theories predict. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[1] |
| limitation | The description that names the paper stops applying at two layers, and the authors say where. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[2] |
| limitation | The explanation offered for the anomalous conductivity is qualitative and rests on an assumption the paper flags as an assumption. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[3] |
| limitation | The theoretical prediction of the effect arrived from groups who did not know the experiment existed. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | limitations[4] |
finding · quantity · variable · definition · key-term — grounded in the full text| finding | In graphene, electron transport is governed by the DIRAC equation: charge carriers behave as massless relativistic particles with effective speed c*≈10^6 m/s — a 2D gas of Dirac fermions. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.findings[0] |
| finding | The integer quantum Hall effect in graphene is anomalous, occurring at half-integer filling factors, and graphene's conductivity never falls below a minimum value. Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.findings[1] |
| evidence status note | finding — QUOTE REPAIRED: the extractor split a hyphen-space and the quote was recorded faithfully with the damage in it, which made it unanchorable. The repaired string is an EXACT SUBSTRING of the staged text - that is why it was accepted, not because a rule produced it. The text as originally recorded is kept in evidence as extracted. | content_tags.findings[1] |
| quantity | c* ≈ 10^6 m/s — effective speed of light of massless charge carriers in graphene Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.quantities[0] |
| quantity | half-integer — anomalous filling factors of the graphene quantum Hall effect Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.quantities[1] |
| evidence status note | quantity — QUOTE REPAIRED: the extractor split a hyphen-space and the quote was recorded faithfully with the damage in it, which made it unanchorable. The repaired string is an EXACT SUBSTRING of the staged text - that is why it was accepted, not because a rule produced it. The text as originally recorded is kept in evidence as extracted. | content_tags.quantities[1] |
| quantity | π — Berry phase shift exhibited by the Dirac fermions Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.quantities[2] |
| variable | Hall conductivity (dependent) Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.variables[1] |
| definition | massless Dirac fermions Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.definitions[0] |
| definition | quantum Hall effect Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.definitions[1] |
| evidence status note | definition — QUOTE REPAIRED: the extractor split a hyphen-space and the quote was recorded faithfully with the damage in it, which made it unanchorable. The repaired string is an EXACT SUBSTRING of the staged text - that is why it was accepted, not because a rule produced it. The text as originally recorded is kept in evidence as extracted. | content_tags.definitions[1] |
| key-terms | graphene, Dirac, massless, carriers, quantum Hall, relativistic, mobility, fermions, half-integer |
| concept | Dirac fermion Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[1] |
| concept | rest mass Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[4] |
| concept | cyclotron mass Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[5] |
| concept | pseudospin Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[6] |
| concept | Dirac equation Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | concepts[7] |
| mean μ | as written: average value Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher. | content_tags.statistics[0] |
When we have changed our mind. Some entries in the table begin with a word in capitals and the reason for it. EVIDENCE CORRECTED — the finding still stands, but we had quoted the wrong sentence from the paper, and the quotation has been replaced with the right one. RETRACTED — the entry itself was wrong; it stays on the page, marked, with the reason, rather than being deleted. WITHDRAWN AND REPLACED — the entry was wrong, and a corrected version of it appears in the entries below. Each mark carries its own reason, in brackets, because the reasons differ from one entry to the next. An entry we have WITHDRAWN is removed from this page and kept in the record, with its reason. A line reading Audit and a date is a later re-reading of the entry against its whole sentence: DOUBTFUL means it was kept, and the reason says what is loose about it. Quotation marks inside the tagger's sentence. Where a tag is the tagger's own sentence, a phrase in quotation marks inside it is borrowed from the paper — the tagger's wording around it is not. The paper's own sentence is the evidence quote for that row; on this page it is withheld with the article, and the article is at its publisher. Nothing inside quotation marks anywhere on this page is ours: if it is quoted, it is the paper's. Whose words a concept carries. A concept entry records a term the paper itself uses, so the term, the sense given for it, and its evidence are the paper's own words, quoted where the paper fixes them. This is the opposite of a sense entry in the tag table, which is the tagger's sentence about how the paper uses a term. Where a concept entry could not be grounded in the paper's words, the entry says so on its own row.
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