$text{UTe}_2$ is a leading candidate for chiral p-wave superconductivity, and for hosting exotic Majorana fermion quasiparticles. Motivated by recent STM experiments in this system, we study particle-hole symmetry breaking in chiral p-wave supercondu
ctors. We compute the local density of states from Majorana fermion surface states in the presence of Rashba surface spin-orbit coupling, which is expected to be sizeable in heavy-fermion materials like UTe$_2$. We show that time-reversal and surface reflection symmetry breaking lead to a natural pairing tendency towards a triplet pair density wave state, which naturally can account for broken particle-hole symmetry.
We study the critical properties of the non-interacting integer quantum Hall to insulator transition (IQHIT) in a dual composite-fermion (CF) representation. A key advantage of the CF representation over electron coordinates is that at criticality, $
textit{CF states are delocalized at all}$ energies. The CF approach thus enables us to study the transition from a new vantage point. Using a lattice representation of CF mean-field theory, we compute the critical and multifractal exponents of the IQHIT. We obtain $ u = 2.56 pm 0.02$ and $eta = 0.51pm 0.01$, both of which are consistent with the predictions of the Chalker-Coddington network model formulated in the electron representation.
The interplay of interactions and disorder in two-dimensional (2D) electron systems has actively been studied for decades. The paradigmatic approach involves starting with a clean Fermi liquid and perturbing the system with both disorder and interact
ions. We instead start with a clean non-Fermi liquid near a 2D ferromagnetic quantum critical point and consider the effects of disorder. In contrast with the disordered Fermi liquid, we find that our model does not suffer from runaway flows to strong coupling and the system has a marginally stable fixed point with perfect conduction.
We construct a three-dimensional (3D), time-reversal symmetric generalization of the Chalker-Coddington network model for the integer quantum Hall transition. The novel feature of our network model is that in addition to a weak topological insulator
phase already accommodated by the network model framework in the pre-existing literature, it hosts strong topological insulator phases as well. We unambiguously demonstrate that strong topological insulator phases emerge as intermediate phases between a trivial insulator phase and a weak topological phase. Additionally, we found a non-local transformation that relates a trivial insulator phase and a weak topological phase in our network model. Remarkably, strong topological phases are mapped to themselves under this transformation. We show that upon adding sufficiently strong disorder the strong topological insulator phases undergo phase transitions into a metallic phase. We numerically determine the critical exponent of the insulator-metal transition. Our network model explicitly shows how a semi-classical percolation picture of topological phase transitions in 2D can be generalized to 3D and opens up a new venue for studying 3D topological phase transitions.
We study the role of electron-electron interactions near quantum Hall (QH) transitions using a composite fermion (CF) representation. While the transition is described by a strong-coupling fixed point, we are nevertheless able to deduce two of its pr
operties. With $1/r$ interactions, 1) the transition has a dynamical exponent $z=1$, and 2) all transitions are `superuniversal: fractional and integer QH transitions belong to the same universality class. With short-range interactions, $z=2$ and the fate of superuniversality remains unclear. To support our observations, we specifically study Sons Dirac CF theory at finite density, in the presence of a random vector potential. Without gauge fluctuations, the system is equivalent to a `dual CF network model. With gauge fluctuations, the system is governed by a gauged nonlinear sigma model (NLSM) with non-zero $theta$-term.
Variations of critical temperature $T_c$ and in-plane critical field $H_{c2}$ of $text{Sr}_2text{Ru}text{O}_4$ under uniaxial stress have recently been reported. We compare the strain dependence of $T_c$ and $H_{c2}$ in various pairing channels ($d$-
wave, extended s-wave and $p$-wave) with the experimental observations, by studying a three-band tight-binding model that includes effects of spin-orbit and Zeeman couplings and a separable pairing interaction. Our study helps narrow down the possibility of pairing channels. The importance of the multi-band nature of $text{Sr}_2text{Ru}text{O}_4$ is also highlighted.
The N$_2$ and CO-rich and water-depleted comet C/2016 R2 (Pan-STARRS) (hereafter `C/2016 R2) is a unique comet for detailed spectroscopic analysis. We aim to explore the associated photochemistry of parent species, which produces different metastable
states and forbidden emissions, in this cometary coma of peculiar composition. We re-analyzed the high-resolution spectra of comet C/2016 R2, which were obtained in February 2018, using the UVES spectrograph of the European Southern Observatory (ESO) Very Large Telescope (VLT). Various forbidden atomic emission lines of [CI], [NI], and [OI] were observed in the optical spectrum of this comet when it was at 2.8 au from the Sun. The observed forbidden emission intensity ratios are studied in the framework of a couple-chemistry emission model. The model calculations show that CO$_2$ is the major source of both atomic oxygen green and red-doublet emissions in the coma of C/2016 R2 (while for most comets it is generally H$_2$O), whereas, CO and N$_2$ govern the atomic carbon and nitrogen emissions, respectively. Our modelled oxygen green to red-doublet and carbon to nitrogen emission ratios are higher by a factor {of 3}, when compared to the observations. These discrepancies can be due to uncertainties associated with photon cross sections or unknown production/loss sources. Our modelled oxygen green to red-doublet emission ratio is close to the observations, when we consider an O$_2$ abundance with a production rate of 30% relative to the CO production rate. The collisional quenching is not a significant loss process for N($^2$D) though its radiative lifetime is significant ($sim$10 hrs). Hence, the observed [NI] doublet-emission ratio ([NI] 5198/5200) of 1.22, which is smaller than the terrestrial measurement by a factor {1.4}, is mainly due to the characteristic radiative decay of N($^2$D).
We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from s
tacked images formed by rotating the cluster-centered Stokes $Q/U$ map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500 deg$^{2}$ survey at the locations of roughly 18,000 clusters with richness $lambda ge 10$ from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at $4.8sigma$. The mean stacked mass of the selected sample is found to be $(1.43 pm 0.4) times 10^{14} {rm M_{odot}}$ which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements.
A recent experimental study [Pan et al., arXiv: 1902.10262] has shown that fractional quantum Hall effect gaps are essentially consistent with particle-hole symmetry in the lowest Landau level. Motivated by this result, we consider a clean two dimens
ional electron system (2DES) from the viewpoint of composite fermion mean-field theory. In this short note, we show that while the experiment is manifestly consistent with a Dirac composite fermion theory proposed recently by Son, it can equally well be explained within the framework of non-relativistic composite fermions, first put forward by Halperin, Lee, and Read.
We use cosmic microwave background (CMB) temperature maps from the 500 deg$^{2}$ SPTpol survey to measure the stacked lensing convergence of galaxy clusters from the Dark Energy Survey (DES) Year-3 redMaPPer (RM) cluster catalog. The lensing signal i
s extracted through a modified quadratic estimator designed to be unbiased by the thermal Sunyaev-Zel{}dovich (tSZ) effect. The modified estimator uses a tSZ-free map, constructed from the SPTpol 95 and 150 GHz datasets, to estimate the background CMB gradient. For lensing reconstruction, we employ t
