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Dive into the research topics where Rajesh Narayanan is active.

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Featured researches published by Rajesh Narayanan.


Physical Review Letters | 2001

Strong Enhancement of SuperconductingTcin Ferromagnetic Phases

T. R. Kirkpatrick; D. Belitz; Thomas Vojta; Rajesh Narayanan

It is shown that the critical temperature for spin-triplet, p-wave superconductivity mediated by spin fluctuations is generically much higher in a Heisenberg ferromagnetic phase than in a paramagnetic one, due to the coupling of the magnons to the longitudinal magnetic susceptibility. Together with the tendency of the low-temperature ferromagnetic transition in very clean Heisenberg magnets to be of first order, this qualitatively explains the phase diagram recently observed in UGe(2).


European Physical Journal B | 1997

Quantum critical behavior of clean itinerant ferromagnets

Thomas Vojta; D. Belitz; Rajesh Narayanan; T. R. Kirkpatrick

We consider the quantum ferromagnetic transition at zero temperature in clean itinerant electron systems. We find that the Landau-Ginzburg-Wilson order parameter field theory breaks down since the electron-electron interaction leads to singular coupling constants in the Landau- Ginzburg-Wilson functional. These couplings generate an effective long-range interaction between the spin or order parameter fluctuations of the form 1 <r2d−1, with d the spatial dimension. This leads to unusual scaling behavior at the quantum critical point in 1 < d ≤ 3, which we determine exactly. We also discuss the quantum-to-classical crossover at small but finite temperatures, which is characterized by the appearance of multiple temperature scales. A comparison with recent results on disordered itinerant ferromagnets is given.


Physical Review B | 2015

Emerging Criticality in the Disordered Three-Color Ashkin-Teller Model

Qiong Zhu; Xin Wan; Rajesh Narayanan; José A. Hoyos; Thomas Vojta

We study the effects of quenched disorder on the first-order phase transition in the two-dimensional three-color Ashkin-Teller model by means of large-scale Monte Carlo simulations. We demonstrate that the first-order phase transition is rounded by the disorder and turns into a continuous one. Using a careful finite-size-scaling analysis, we provide strong evidence for the emerging critical behavior of the disordered Ashkin-Teller model to be in the clean two-dimensional Ising universality class, accompanied by universal logarithmic corrections. This agrees with perturbative renormalization-group predictions by Cardy. As a byproduct, we also provide support for the strong-universality scenario for the critical behavior of the two-dimensional disordered Ising model. We discuss consequences of our results for the classification of disordered phase transitions as well as generalizations to other systems.


Physical Review Letters | 1999

Influence of Rare Regions on Magnetic Quantum Phase Transitions

Rajesh Narayanan; Thomas Vojta; D. Belitz; T. R. Kirkpatrick

The effects of quenched disorder on the critical properties of itinerant quantum magnets are considered. Particular attention is paid to locally ordered rare regions that are formed in the presence of quenched disorder even when the bulk system is still in the nonmagnetic phase. It is shown that these local moments or instantons destroy the previously found critical fixed point in the case of antiferromagnets. In the case of itinerant ferromagnets, the critical behavior is unaffected by the rare regions due to an effective long-range interaction between the order parameter fluctuations.


Physical Review Letters | 2014

Density of states in graphene with vacancies: midgap power law and frozen multifractality

Victor Häfner; J. Schindler; N. Weik; T. Mayer; S. Balakrishnan; Rajesh Narayanan; Soumya Bera; Ferdinand Evers

The density of states ϱ(E) of graphene is investigated numerically and within the self-consistent T-matrix approximation in the presence of vacancies within the tight binding model. The focus is on compensated disorder, where the concentration of vacancies n(A) and n(B) in both sublattices is the same. Formally, this model belongs to the chiral symmetry class BDI. The onlinear sigma model predicts for BDI a Gade-type singularity ϱ(E)∼|E|(-1)exp[-|log(E)|(-1/x)]. Our numerical data are comparable to this result in a preasymptotic regime that gives way, however, at even lower energies to ϱ(E)∼E(-1)|log(E)|(-x̃), 1≤x̃<2. We take this finding as evidence that, similar to the case of dirty d-wave superconductors, generic bipartite random hopping models may also exhibit unconventional (strong-coupling) fixed points for certain kinds of randomly placed scatterers if these are strong enough. Our research suggests that graphene with (effective) vacancy disorder is a physical representative of such systems.


Physical Review B | 2012

Fractional quantum Hall states in two-dimensional electron systems with anisotropic interactions

Hao Wang; Rajesh Narayanan; Xin Wan; Fu-Chun Zhang

We study the anisotropic effect of the Coulomb interaction on a 1/3-filling fractional quantum Hall system by using an exact diagonalization method on small systems in torus geometry. For weak anisotropy the system remains to be an incompressible quantum liquid, although anisotropy manifests itself in density correlation functions and excitation spectra. When the strength of anisotropy increases, we find the system develops a Hall-smectic-like phase with a one-dimensional charge density wave order and is unstable towards the one-dimensional crystal in the strong anisotropy limit. In all three phases of the Laughlin liquid, Hall-smectic-like, and crystal phases the ground state of the anisotropic Coulomb system can be well described by a family of model wave functions generated by an anisotropic projection Hamiltonian. We discuss the relevance of the results to the geometrical description of fractional quantum Hall states proposed by Haldane [ Phys. Rev. Lett. 107 116801 (2011)].


EPL | 1996

Breakdown of Landau-Ginzburg-Wilson theory for certain quantum phase transitions

Thomas Vojta; D. Belitz; Rajesh Narayanan; T. R. Kirkpatrick

The quantum ferromagnetic transition of itinerant electrons is considered. It is shown that the Landau-Ginzburg-Wilson theory described by Hertz and others breaks down due to a singular coupling between fluctuations of the conserved order parameter. This coupling induces an effective long-range interaction between the spins of the form 1/r2d − 1. It leads to unusual scaling behavior at the quantum critical point in 1 < d ≤ 3 dimensions, which is determined exactly.


Physical Review B | 2016

Intertwined nematic orders in a frustrated ferromagnet

Yasir Iqbal; Pratyay Gosh; Rajesh Narayanan; Brijesh Kumar; Johannes Reuther; Ronny Thomale

We investigate the quantum phases of the frustrated spin-


Physical Review B | 2011

Dissipative spin dynamics near a quantum critical point: Numerical renormalization group and Majorana diagrammatics

Serge Florens; Axel Freyn; Davide Venturelli; Rajesh Narayanan

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Physical Review B | 1999

Critical Behavior of Disordered Quantum Magnets: The Relevance of Rare Regions

Rajesh Narayanan; Thomas Vojta; D. Belitz; T. R. Kirkpatrick

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Thomas Vojta

Missouri University of Science and Technology

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Priyanka Mohan

Indian Institute of Technology Madras

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Serge Florens

Joseph Fourier University

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Ferdinand Evers

Karlsruhe Institute of Technology

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José A. Hoyos

Missouri University of Science and Technology

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Fawaz Hrahsheh

Missouri University of Science and Technology

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A. D. Mirlin

Karlsruhe Institute of Technology

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A. Mildenberger

Karlsruhe Institute of Technology

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