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P. Jiang

Publications and source records attributed to P. Jiang.

32 records · Page 2Linked to original sources
arXiv2020

Diverse polarization angle swings from a repeating fast radio burst source

Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown origin. Two possible mechanisms that could generate extremely coherent emission from FRBs invoke neutron star magnetospheres or relativistic shocks far from the central energy source. Detailed polarization observations may help us to understand the emission mechanism. However, the available FRB polarization data have been perplexing, because they show a host of polarimetric properties, including either a constant polarization angle during each burst for some repeaters or variable polarization angles in some other apparently one-off events. Here we report observations of 15 bursts from FRB 180301 and find various polarization angle swings in seven of them. The diversity of the polarization angle features of these bursts is consistent with a magnetospheric origin of the radio emission, and disfavours the radiation models invoking relativistic shocks.

astro-ph.HE↗
arXiv2013

Reference frame independent quantum key distribution server with telecom tether for on-chip client

We demonstrate a client-server quantum key distribution (QKD) scheme, with large resources such as laser and detectors situated at the server-side, which is accessible via telecom-fibre, to a client requiring only an on-chip polarisation rotator, that may be integrated into a handheld device. The detrimental effects of unstable fibre birefringence are overcome by employing the reference frame independent QKD protocol for polarisation qubits in polarisation maintaining fibre, where standard QKD protocols fail, as we show for comparison. This opens the way for quantum enhanced secure communications between companies and members of the general public equipped with handheld mobile devices, via telecom-fibre tethering.

quant-ph↗
arXiv2011

Braiding of Abelian and Non-Abelian Anyons in the Fractional Quantum Hall Effect

In this paper, we report on the study of Abelian and non-Abelian statistics through Fabry-Perot interferometry of fractional quantum Hall (FQH) systems. Our detection of phase slips in quantum interference experiments demonstrates a powerful, new way of detecting braiding of anyons. We confirm the Abelian anyonic braiding statistics in the $ν= 7/3$ FQH state through detection of the predicted statistical phase angle of $2π/3$, consistent with a change of the anyonic particle number by one. The $ν= 5/2$ FQH state is theoretically believed to harbor non-Abelian anyons which are Majorana, meaning that each pair of quasiparticles contain a neutral fermion orbital which can be occupied or unoccupied and hence can act as a qubit. In this case our observed statistical phase slips agree with a theoretical model where the Majoranas are strongly coupled to each other, and strongly coupled to the edge modes of the interferometer. In particular, an observed phase slip of approximately $π$ is interpreted as a sudden flip of a qubit, or entry of a neutral fermion into the interferometer. Our results provide compelling support for the existence of non-Abelian anyons.

cond-mat.mes-hall↗
arXiv2011

Zero-Bias Anomalies in Narrow Tunnel Junctions in the Quantum Hall Regime

We report on the study of cleaved-edge-overgrown line junctions with a serendipitously created narrow opening in an otherwise thin, precise line barrier. Two sets of zero-bias anomalies are observed with an enhanced conductance for filling factors $ν> 1$ and a strongly suppressed conductance for $ν< 1$. A transition between the two behaviors is found near $ν\approx 1$. The zero-bias anomaly (ZBA) line shapes find explanation in Luttinger liquid models of tunneling between quantum Hall edge states. The ZBA for $ν< 1$ occurs from strong backscattering induced by suppression of quasiparticle tunneling between the edge channels for the $n = 0$ Landau levels. The ZBA for $ν> 1$ arises from weak tunneling of quasiparticles between the $n = 1$ edge channels.

cond-mat.mes-hall↗
arXiv2010

A Dusty Mg~II absorber Associated with the Quasar SDSS J003545.13+011441.2

We report on a dusty Mg~II absorber associated with the quasar SDSSJ003545.13+011441.2 (hereafter J0035+0114) at $z$=1.5501, which is the strongest one among the three Mg~II absorbers along the sight line of quasar. The two low redshift intervening absorbers are at $z$=0.7436, 0.5436, respectively. Based on the photometric and spectroscopic data of Sloan Digital Sky Survey (hereafter SDSS), we infer the rest frame color excess E(\bv) due to the associated dust is more than 0.07 by assuming a Small Magellanic Cloud (hereafter SMC) type extinction curve. Our follow-up moderate resolution spectroscopic observation at the 10-m Keck telescope with the ESI spectrometer enable us to reliably identify most of the important metal elements, such as Zn, Fe, Mn, Mg, Al, Si, Cr, and Ni in the associated system. We measure the column density of each species and detect significant dust depletion. In addition, we develop a simulation technique to gauge the significance of 2175-Å dust absorption bump on the SDSS quasar spectra. By using it, we analyze the SDSS spectrum of J0035+0114 for the presence of a associated 2175-Å extinction feature and report a tentative detection at $\sim$2$σ$ significant level.

astro-ph.CO↗
arXiv2010

Observation of pinning mode in Wigner solid of 1/3 fractional quantum Hall excitations

We report the observation of a resonance in the microwave spectra of the real diagonal conductivities of a two-dimensional electron system within a range of ~ +- .0.015 $ from filling factor $ν=1/3$. The resonance is remarkably similar to resonances previously observed near integer $ν$, and is interpreted as the collective pinning mode of a disorder-pinned Wigner solid phase of $e/3$-charged carriers .

cond-mat.mes-hall↗
arXiv2007

Are Seyfert 2 Galaxies without Polarized Broad Emission Lines More Obscured?

The new $XMM-Newton$ data of seven Seyfert 2 galaxies with optical spectropolarimetric observations are presented. The analysis of 0.5 -- 10 keV spectra shows that all four Seyfert 2 galaxies with polarized broad lines (PBLs) are absorbed with $N_{\rm H}<10^{24}$ cm$^{-2}$, while two of three Seyfert 2 galaxies without PBLs have evidence suggesting Compton-thick obscuration, supporting the conclusion that Seyfert 2 galaxies without PBLs are more obscured than those with PBLs. Adding the measured obscuration indicators ($N_{\rm H}$, $T$ ratio, and Fe K$α$ line EW) of six luminous AGNs to our previous sample improves the significance level of the difference in absorption from 92.3% to 96.3% for $N_{\rm H}$, 99.1% to 99.4% for $T$ ratio, and 95.3% to 97.4% for Fe K$α$ line EW. The present results support and enhance the suggestions that the absence of PBLs in Seyfert 2 galaxies can be explained by larger viewing angle of line of sight to the putative dusty torus, which lead to the obscuration of broad-line scattering screen, as expected by the unification model.

astro-ph↗
arXiv2007

Aharonov-Bohm-Like Oscillations in Quantum Hall Corrals

Experimental study of quantum Hall corrals reveals Aharonov-Bohm-Like (ABL) oscillations. Unlike the Aharonov-Bohm effect which has a period of one flux quantum, $Φ_{0}$, the ABL oscillations possess a flux period of $Φ_{0}/f$, where $f$ is the integer number of fully filled Landau levels in the constrictions. Detection of the ABL oscillations is limited to the low magnetic field side of the $ν_{c}$ = 1, 2, 4, 6... integer quantum Hall plateaus. These oscillations can be understood within the Coulomb blockade model of quantum Hall interferometers as forward tunneling and backscattering, respectively, through the center island of the corral from the bulk and the edge states. The evidence for quantum interference is weak and circumstantial.

cond-mat.mes-hall↗
arXiv2006

Most hard X-ray selected quasars in Chandra Deep Fields are obscured

Measuring the population of obscured quasars is one of the key issues to understand the evolution of active galactic nuclei (AGNs). With a redshift completeness of 99%, the X-ray sources detected in Chandra Deep Field South (CDF-S) provide the best sample for this issue. In this letter we study the population of obscured quasars in CDF-S by choosing the 4 -- 7 keV selected sample, which is less biased by the intrinsic X-ray absorption. The 4 -- 7 keV band selected samples also filter out most of the X-ray faint sources with too few counts, for which the measurements of N_H and L_X have very large uncertainties. Simply adopting the best-fit L_2-10keV and N_H, we find 71% (20 out of 28) of the quasars (with intrinsic L_2-10keV > 10^44 erg/s) are obscured with N_H > 10^22 cm^-2. Taking account of the uncertainties in the measurements of both N_H and L_X, conservative lower and upper limits of the fraction are 54% (13 out 24) and 84% (31 out 37). In Chandra Deep Field North, the number is 29%, however, this is mainly due to the redshift incompleteness. We estimate a fraction of ~ 50% - 63% after correcting the redshift incompleteness with a straightforward approach. Our results robustly confirm the existence of a large population of obscured quasars.

astro-ph↗
arXiv2006

Investigating on the nuclear obscuration in two types of Seyfert 2 galaxies

We build a large sample of Seyfert 2 galaxies (Sy2s) with both optical spectropolarimetric and X-ray data available, in which 29 Sy2s with the detection of polarized broad emission line (PBL) and 25 without. We find that for luminous Sy2s with L_[OIII] > 10^41 erg/s, sources with PBL have smaller X-ray absorption column density comparing with those without PBL (at 92.3% confidence level): most of the Sy2s with N_H<10^23.8 cm^-2 show PBL (86%, 12 out 14), while the fraction is much smaller for sources with heavier obscuration (54%, 15 out 28). The confidence level of the difference in absorption bounces up to 99.1% while using the "T" ratio (F_2-10keV/F_[O III]) as an indicator. We rule out observation or selection bias as the origin for the difference. Our results, for the first time with high statistical confidence, show that, in additional to the nuclei activity, the nuclear obscuration also plays an important role in the visibility of PBL in Sy2s. These results can be interpreted in the framework of the unified model. We can reach these results in the unified model if: a) the absorption column density is higher at large inclinations and b) the scattering region is obscured at large inclinations.

astro-ph↗
arXiv2006

On the fraction of X-ray obscured quasars in the local universe

Recent wide area hard X-ray and soft Gamma ray surveys have shown that the fraction of X-ray obscured AGNs in the local universe significantly decreases with intrinsic luminosity. In this letter we point out that two correction have to be made to the samples: 1) radio loud AGNs have to be excluded since their X-ray emission might be dominated by the jet component; 2) Compton thick sources have to be excluded too since their hard X-ray and soft gamma ray emission are also strongly attenuated by Compton scattering. The soft gamma-ray selected AGN samples obtained by SWIFT and INTEGRAL provide the best opportunity to study the fraction of obscured AGN in the local universe in the least biased way. We choose these samples to check if the corrections could alter the above result on the fraction of obscured AGNs. We find that before the corrections both samples show significant anti-correlation between L_X and N_H, indicating obvious decrease in the fraction of obscured AGNs with luminosity. However, after the corrections, we find only marginal evidence of anti-correlation (at 98% confidence level) in the SWIFT sample, and no evidence at all in the INTEGRAL sample which consists of comparable number of objects. We conclude that current samples only show a marginal decrease in the fraction of obscured AGNs in the local universe, and much larger samples are required to reach a more robust conclusion.

astro-ph↗
arXiv2006

On the X-ray Baldwin effect for narrow Fe Kalpha emission line

Most Active Galactic Nuclei (AGN) exhibit a narrow Fe Kalpha line at ~ 6.4 keV in the X-ray spectra, due to the fluorescent emission from cold material far from the inner accretion disk. Using XMM-Newton observations, Page et al. found that the equivalent width (EW) of the narrow Fe Kalpha line decreases with increasing luminosity (EW ~ L^-0.17pm0.08), suggesting a decrease in the covering factor of the material emitting the line (presumably the torus). By combining the archival Chandra HETG observations of 34 type 1 AGNs with XMM observations in literature, we build a much large sample with 101 AGNs. We find a similar X-ray Baldwin effect in the sample (EW ~ L^-0.2015pm0.0426), however, we note that the anti-correlation is dominated by the radio loud AGN in the sample, whose X-ray spectra might be contaminated by the relativistic jet. Excluding the radio loud AGN, we find a much weaker anti-correlation (EW ~ L^-0.1019pm0.0524). We present Monte-Carlo simulations showing that such a weak anti-correlation can be attributed to the relative short time scale variations of the X-ray continuum.

astro-ph↗
arXiv2006

Interaction Effects and Pseudogap in Two-Dimensional Lateral Tunnel Junctions

Tunneling characteristics of a two-dimensional lateral tunnel junction (2DLTJ) are reported. A pseudogap on the order of Coulomb energy is detected in the tunneling density of states (TDOS) when two identical two-dimensional electron systems are laterally separated by a thin energy barrier. The Coulombic pseudogap remains robust well into the quantum Hall regime until it is overshadowed by the cyclotron gap in the TDOS. The pseudogap is modified by in-plane magnetic field, demonstrating a non-trivial effect of in-plane magnetic field on the electron-electron interaction.

cond-mat.mes-hall↗