arXiv subjects

Sumiran Pujari

Publications and source records attributed to Sumiran Pujari.

41 records · Page 3Linked to original sources

arXiv2013

Néel to valence-bond solid transition on the honeycomb lattice: Evidence for deconfined criticality

We study a spin-1/2 SU(2) model on the honeycomb lattice with nearest-neighbor antiferromagnetic exchange $J$ that favors Néel order, and competing 6-spin interactions $Q$ which favor a valence bond solid (VBS) state in which the bond-energies order at the "columnar" wavevector ${\mathbf K} = (2π/3,-2π/3)$. We present quantum Monte-Carlo evidence for a direct continuous quantum phase transition between Néel and VBS states, with exponents and logarithmic violations of scaling consistent with those at analogous deconfined critical points on the square lattice. Although this strongly suggests a description in terms of deconfined criticality, the measured three-fold anisotropy of the phase of the VBS order parameter shows unusual near-marginal behaviour at the critical point.

cond-mat.str-el↗

arXiv2012

Effect of Dirac Spinons on ARPES signatures of Herbertsmithe

The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To solidify evidence for its existence, we address the question of what will be the Angle Resolved Photoemission Spectroscopy (ARPES) signatures of single crystal samples of Herbertsmithite assuming it is described by the Dirac spin liquid state. In particular, we show that the electron spectral function will have a linear in energy dependence near specific wave vectors and that this dependence is expected even after fluctuations to the mean field values are taken into account. Observation of this unique signature in ARPES will provide very strong evidence for the existence of spinons in greater than one dimension.

cond-mat.str-el↗

arXiv2011

Extracting Quasiparticle Lifetimes from STM experiments

Based on Quasiparticle Interference(QPI) around a point impurity, we demonstrate an analysis scheme that extracts the lifetime of a quasiparticle by using the Local Density of States(LDOS) data around the impurity in a Scanning Tunneling Microscopy(STM) experiment. This data analysis scheme would augment the Fourier-Transform Scanning Tunneling Spectroscopic method which provides us with the quasiparticle dispersion. Thus, point impurities can be used as probes to extract quasiparticle lifetimes from STM experiments and this would complement other experimental methods such as Angle Resolved Photo-emission Spectrocopy(ARPES). We detail how the scheme would apply to conventional metals/Fermi Liquids and Superconductors.

cond-mat.str-el↗

arXiv2009

Echolocation by Quasiparticles

It is shown that the local density of states (LDOS), measured in an Scanning Tunneling Microscopy (STM) experiment, at a single tip position contains oscillations as a function of Energy, due to quasiparticle interference, which is related to the positions of nearby scatterers. We propose a method of STM data analysis based on this idea, which can be used to locate the scatterers. In the case of a superconductor, the method can potentially distinguish the nature of the scattering by a particular impurity.

cond-mat.supr-con↗

arXiv2008

Spontaneous Currents in Spinless Fermion Lattice Models at the Strong-Coupling Limit

What kind of lattice Hamiltonian manifestly has an ordered state with spontaneous orbital currents? We consider interacting spinless fermions on an array of square plaquettes, connected by weak hopping; the array geometry may be a 2 x 2L ladder, a 2 x 2 x 2L "tube", or a 2L x 2L square grid. At half filling, we derive an effective Hamiltonian in terms of pseudospins, of which one component represents orbital currents, and find the conditions sufficient for orbital current long-range order. We consider spinfull variants of the aforesaid spinless models and make contact with other spinfull models in the literature purported to possess spontaneous currents.

cond-mat.str-el↗