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ASASSN-20hx, a.k.a AT2020ohl, is an ambiguous nuclear transient (ANT), which was discovered in the nearby galaxy NGC6297 by the All-Sky Automated Survey for Supernovae (ASAS-SN). We have investigated the evolution of AT2020ohl using a multi-wavelength dataset to explain the geometry of the system and the energy radiated by it between X-ray and radio wavelengths. Our X-ray, UV/optical, and radio observations of the object jointly clarify the association of AT2020ohl with the nuclear activity of NGC6297. We detected radio counterpart of AT2020ohl 111 days and 313 days after the discovery in Jansky Very Large Array X-band with flux densities 47$\pm$14 $\mu$Jy and 34$\pm$3 $\mu$Jy, respectively. Using multi-wavelength data analysis, we nullify the possibility of associating any stellar disruption process with this event. We found some evidence showing that the host galaxy is a merger remnant, so the possibility of a binary SMBH system can not be ruled out. The central SMBH has a mass of $\sim1.2\times10^7$ M$_\odot$. We propose the accretion disk activity as the origin of AT2020ohl $-$ it is either due to disk accretion event onto the central SMBH or due to the sudden accretion activity in a preexisting accretion disk of the system during the interaction of two SMBHs which became gravitationally bound during a merger process. However, we also admit that with the existing dataset, it is impossible to say definitively, among these two probabilities, which one is the origin of this nuclear transient., Comment: 17 pages, 9 figures. Published in MNRAS ( see https://doi.org/10.1093/mnras/stae395 )

The effect of Hubbard and Kondo interactions on the edge states in the half-filled Su-Schrieffer-Heeger chain of electrons is investigated by studying the behaviour of charge quasiparticles using Kumar representation and density matrix renormalization group method. For any finite dimerization of hopping, by increasing the Hubbard interaction, the edge states are found to transmigrate from the physical charge gap to a high energy gap through an intermediate phase without the edge states. The extent of this phase with no edge states shrinks smoothly upon increasing the dimerization. The transmigration of edge states from the charge gap to the high energy gap is also found to occur with Kondo interaction, but through an intermediate phase which itself changes from having no edge states for weak dimerization to having the edge states in the physical as well as the high energy gaps coexisting from moderate to strong dimerization., Comment: 7+ pages, 14 figures

Investigating the polarization properties of light in the mid-infrared (mid-IR) spectrum is crucial for molecular sensing, biomedical diagnostics, and IR imaging system technologies. Traditional methods, limited by bulky size and intricate fabrication, utilize large rotating optics for full Stokes polarization detection, impeding miniaturization and accuracy. Van der Waals materials (vdW) based devices can address these challenges due to their lithography-free fabrication, ease of integration with chip-scale platforms and room-temperature operation. This study introduces a chip-integrated polarimeter device leveraging the in-plane biaxial hyperbolic vdW crystal properties for mid-infrared light manipulation. The spatial division measurement scheme incorporates six meticulously designed linear and circular polarization filters, achieving high extinction ratios exceeding 30 dB and transmittance surpassing 50%, with fabrication tolerance of film thickness up to 100 nm. The proposed device represents a significant advancement in polarimetric detection, providing a compact, cost-effective solution and opens new avenues for on-chip mid-IR polarimetric detection in next-generation ultra-compact optical systems.

In the realm of quantum information and sensing, there has been substantial interest in the single-photon emission associated with defects in hexagonal boron nitride (hBN). With the goal of producing deterministic emission centers, in this work, we present a platform for engineering emission in hBN integrated with gold truncated nanocone structures. Our findings highlights that, the activation of emission is due to the truncated gold nanocones. Furthermore, we measure the quantum characteristics of this emission and find that while our system demonstrates support for single-photon emission, the origin of this emission remains ambiguous. Specifically, it is unclear whether the emission arises from defects generated by the induced strain or from alternative defect mechanisms. This uncertainty stems from the fluorescence properties inherent to gold, complicating our definitive attribution of the quantum emission source. To provide a rigorous theoretical foundation, we elucidate the effects of strain via the Kirchhoff-Love theory. Additionally, the enhancements observed due to plasmonic effects are comprehensively explained through the resolution of Maxwell's equations. This study will be useful for the development of deterministic and tunable single photonic sources in two dimensional materials and their integration with plasmonic platforms.

Monolithic integration of solid-state color centers with photonic elements of the same material is a promising approach to overcome the constraints of fabrication complexity and coupling losses in traditional hybrid integration approaches. A wide band-gap, low-loss silicon nitride (SiN) platform is a mature technology, having CMOS compatibility, widely used in hybrid integrated photonics and optoelectronics. However, it has been shown that certain growth conditions enable the SiN material to host color centers, whose origin is currently under investigation. In this work, we have engineered a novel technique for the efficient coupling of these intrinsic emitters into the whispering gallery modes (WGMs) of the SiN microring cavity -- which has not been explored previously. We have engineered a subwavelength-sized notch into the rim of the SiN microring structure, to optimize the collection efficiency of the cavity-coupled enhanced photoluminescence (PL) spectra at room temperature. The platform presented in this work will enable the development of monolithic integration of color centers with nanophotonic elements for application to quantum photonic technologies.

The heightened sensitivity observed in non-Hermitian systems at exceptional points (EPs) has garnered significant attention. Typical EP sensor implementations rely on precise measurements of spectra and importantly, for real time sensing measurements, the EP condition ceases to hold as the perturbation increases over time, thereby preventing the use of high sensitivity at the EP point. In this work, we present an new approach to EP sensing which goes beyond these two traditional constraints. Firstly, instead of measuring the spectra, our scheme of EP based sensing is based on the observation of decay length of the optical mode in finite size gratings, which is validated via coupled mode theory as well as full wave electrodynamic simulations. Secondly, for larger perturbation strengths, the EP is spectrally shifted instead of being destroyed -- this spectral shift of the EP is calibrated and using this look-up table, we propose continuous real time detection by varying the excitation laser wavelength. As a proof of principle of our technique, we present an application to the sensing of coronavirus particles, which shows unprecedented limit of detection. These findings will contribute to the expanding field of exceptional point based sensing technologies for real time applications beyond spectral measurements.

In-plane Hyperbolic Phonon polaritons (HPhPs) are quasiparticles formed via coupling of photons and optical phonons in in-plane hyperbolic materials and offer unique applications in sensing, thermal emitters and high resolution imaging. However, the large momentum mismatch between photons and these in-plane HPhPs has restricted their technological potential as most experimental demonstration rely on sophisticated and expensive near field detection schemes. In this work, using the example of $\alpha-$MoO$_3$, we demonstrate that by constructing photonic hypercrystals of this material, one can not only excite these in-plane HPhPs in the far field but also tune the far field response via twisting the hypercrystal lattice with respect the lattice of $\alpha-$MoO$_3$. Our findings will pave the way for the development of practical in-plane HPhP devices as well as provide access to new fundamental physics of such materials via conventional and well developed far field measurement techniques.

We present photometric and kinematic analysis of an intermediate age open cluster NGC 1027 using $UBV(RI)_c$ and Gaia Early Data Release 3 (EDR3) data. Structural and fundamental parameters such as cluster center, cluster extent, reddening, age and distance are estimated in this study. Cluster center is found about 2 arcmin away from the center reported earlier. Radius has been estimated to be about 8.00 arcmin(2.65pc). Using proper motion Gaia EDR3 data, membership probabilities has been derived for the stars in the region of cluster radius. We find mean proper motion of the cluster to be $\sim$(-0.84, 2.04) mas yr$^{-1}$ in (RA, DEC). We find 217 most probable (P$_\mu>$ 70\%) cluster members with mean parallax 0.892 $\pm$ 0.088 mas. Out of these, 160 members have counterparts in our optical observations. Few stars having P$_\mu>$ 70\% are found out of the cluster radius showing imprints of dynamical evolution. The color-color and color-magnitude diagrams for the cluster members found within 8.00 arcmin have been constructed using $UBV(RI)_c$ photometry and Gaia EDR3 data. This yields a reddening E($B$-$V$) $\sim$ 0.36 mag, age $\sim$ 130 Myr and distance $\sim$ 1.14 kpc. The mass function slope in the cluster region is $\Gamma$ $\sim$ -1.46 $\pm$ 0.15, which is similar to other Galactic open clusters. The dynamical study shows lack of faint stars in its inner region leading to mass segregation effect. A comparison of dynamical age with cluster age indicates that NGC 1027 is a dynamically relaxed cluster suggesting that mass segregation may be imprint of its dynamical relaxation.

We present the idea of emergent qubits by an exact model construction on a trestle, also generalized to arbitrary graphs. The corresponding eigenstates are quantum paramagnetic, with free multipolar moments. We rigorously transform the toric code model on a torus, cylinder and sheet into emergent qubits, writing all the eigenstates exactly. We devise exact quantum circuits for the toric code and other eigenstates described here. The depth of the circuit for toric code eigenstates on torus grows linearly with the total number of qubits, as compared to the sublinear growth on cylinder or sheet., Comment: 9 pages, 7 captioned figures

Strong coupling of excitons to optical cavity modes is of immense importance to understanding the fundamental physics of quantum electrodynamics at the nanoscale as well as for practical applications in quantum information technologies. There have been several attempts at achieving strong coupling between excitons in two dimensional semiconductors such as transition metal dichalcogenides (TMDCs) and photonic quasi-bound states in the continuum (BICs). We identify two gaps in the platforms for achieving strong coupling between TMDC excitons and photonic quasi-BICs: firstly, in the studies so far, different cavity architectures have been employed for coupling to different TMDCs. This would mean that typically, the fabrication process flow for the cavities will need to be modified as one moves from one TMDC to the other, which can limit the technological progress in the field. Secondly, there has been no discussion of the impact of fabrication imperfections in the studies on strong coupling of these subsystems so far. In this work, we address these two questions by optimizing a cavity with the same architecture which can couple to the four typical TMDCs (MoS$_2$, WS$_2$, MoSe$_2$, WSe$_2$) and perform a detailed investigation on the fabrication tolerance of the associated photonic quasi-BICs and their impact on strong coupling.

The half-filled Kondo lattice model is studied at low temperatures on simple cubic lattice using the self-consistent theory developed in Phys. Rev. B 96, 075115 (2017). It is found to have three distinct insulating phases in the temperature-hopping plane, namely, the strong coupling Kondo singlet (KS) phase, the inverted Kondo singlet (iKS) phase distinguished from the KS by inversion, and the antiferromagnetic (AFM) phase. The quasiparticle density of states across the inversion transition is noted to exhibit dimensional reduction, which can differentiate between the KS and iKS insulators in experiments. Magnetic quantum oscillations obtained in the iKS and AFM phases are found to show Lifshitz-Kosevich like behaviour with temperature as well as inverse hopping., Comment: 5 pages, 4 figures

Radio emission from 23 tidal disruption event host galaxies were searched in the 144 MHz LOFAR-LoTSS2 images. Three host galaxies are detected with diffuse radio emission, which can be interpreted as either galactic synchrotron radio emission or diffuse radio halo in dense galactic environments. Non-detection of (transient) radio emission in majority of galaxies could be due to self-absorption of radio emission associated with the tidal disruption event. The detected objects are AT2018iih, RBS 1032, and NGC 5905. Non-detection for Sw 1644+57 is also reported., Comment: 3 pages, 3 figures, In Research Notes AAS (RNAAS)