21 research outputs found
Unifying Interacting Nodal Semimetals: A New Route to Strong Coupling
We propose a general framework for constructing a large set of nodal-point
semimetals by tuning the number of linearly () and (at most) quadratically
() dispersing directions. By virtue of such a unifying scheme, we identify
a new perturbative route to access various strongly interacting non-Dirac
semimetals with . As a demonstrative example, we relate a two
dimensional anisotropic semimetal with , describing the topological
transition between a Dirac semimetal and a normal insulator, and its three
dimensional counterparts with , . We address the quantum critical
phenomena and emergence of non-Fermi liquid states with unusual dynamical
structures within the framework of an expansion, where
, when these systems reside at the brink of charge- or
spin-density-wave orderings, or an -wave pairing. Our results can be germane
to two-dimensional uniaxially strained optical honeymcomb lattice,
-(BEDT-TTF).Comment: 5 pages, 3 figures; Published versio
Multi-criticality and field induced non-BEC transition in frustrated magnets
Frustrated spin-systems have traditionally proven challenging to understand,
owing to a scarcity of controlled methods for their analyses. By contrast,
under strong magnetic fields, certain aspects of spin systems admit simpler and
universal description in terms of hardcore bosons. The bosonic formalism is
anchored by the phenomenon of Bose-Einstein condensation (BEC), which has
helped explain the behaviors of a wide range of magnetic compounds under
applied magnetic fields. Here, we focus on the interplay between frustration
and externally applied magnetic field to identify instances where the BEC
paradigm is no longer applicable. As a representative example, we consider the
antiferromagnetic model on the square lattice in the presence
of a uniform external magnetic field, and demonstrate that the
frustration-driven suppression of the N\'{e}el order leads to a Lifshitz
transition for the hardcore bosons. In the vicinity of the Lifshitz point, the
physics becomes unmoored from the BEC paradigm, and the behavior of the system,
both at and below the saturation field, is controlled by a Lifshitz
multicritical point. We obtain the resultant universal scaling behaviors, and
provide strong evidence for the existence of a frustration and magnetic-field
driven correlated bosonic liquid state along the entire phase boundary
separating the N\'{e}el phase from other magnetically ordered states.Comment: 6 pages; 5 figures; v2) updated references, typos fixed, supplemental
information added as ancillary fil
Topology of SO(5)-monopoles and three-dimensional, stable Dirac semimetals
The band-touching points of stable, three-dimensional, Kramers-degenerate,
Dirac semimetals are singularities of a five-component, unit vector field and
non-Abelian, -Berry's connections, whose topological classification is
an important, open problem. We solve this problem by performing second homotopy
classification of Berry's connections. Using Abelian projected connections, the
generic planes, orthogonal to the direction of nodal separation, and lying
between two Dirac points are shown to be higher-order topological insulators,
which support quantized, chromo-magnetic flux or relative Chern number, and
gapped, edge states. The Dirac points are identified as a pair of
unit-strength, - monopole and anti-monopole, where the relative Chern
number jumps by . Using these bulk invariants, we determine the
topological universality class of different types of Dirac semimetals. We also
describe a universal recipe for computing quantized, non-Abelian flux for Dirac
materials from the windings of spectra of planar Wilson loops, displaying
-gauge invariance. With non-perturbative, analytical solutions of
surface-states, we show the absence of helical Fermi arcs, and predict the
fermiology and the spin-orbital textures. We also discuss the similarities and
important topological distinction between the surface-states Hamiltonian and
the generator of Polyakov loop of Berry's connections.Comment: 19 pages, 8 figure
Electronic properties, correlated topology and Green's function zeros
There is extensive current interest about electronic topology in correlated
settings. In strongly correlated systems, contours of Green's function zeros
may develop in frequency-momentum space, and their role in correlated topology
has increasingly been recognized. However, whether and how the zeros contribute
to electronic properties is a matter of uncertainty. Here we address the issue
in an exactly solvable model for Mott insulator. We show that the Green's
function zeros contribute to several physically measurable correlation
functions, in a way that does not run into inconsistencies. In particular, the
physical properties remain robust to chemical potential variations up to the
Mott gap as it should be based on general considerations. Our work sets the
stage for further understandings on the rich interplay among topology, symmetry
and strong correlations.Comment: 15 pages, 3 figure
Shot noise as a characterization of strongly correlated metals
Shot noise measures out-of-equilibrium current fluctuations and is a powerful
tool to probe the nature of current-carrying excitations in quantum systems.
Recent shot noise measurements in the heavy fermion strange metal
YbRhSi exhibit a strong suppression of the Fano factor () -- the
ratio of the current noise to the average current in the DC limit. This system
is representative of metals in which electron correlations are extremely
strong. Here we carry out the first theoretical study on the shot noise of
diffusive metals in the regime of strong correlations. A Boltzmann-Langevin
equation formulation is constructed in a quasiparticle description in the
presence of strong correlations. We find that in such a
correlation regime. Hence, the Fano factor suppression observed in experiments
on YbRhSi necessitates a loss of the quasiparticles. Our work opens the
door to systematic theoretical studies of shot noise as a means of
characterizing strongly correlated metallic phases and materials.Comment: 6+2 pages, 2+1 figure
Topological Diagnosis of Strongly Correlated Electron Systems
The intersection of electronic topology and strong correlations offers a rich
platform to discover exotic quantum phases of matter and unusual materials. An
overarching challenge that impedes the discovery is how to diagnose topology in
strongly correlated settings, as exemplified by Mott insulators. Here, we
develop a general framework to address this outstanding question and illustrate
its power in the case of Mott insulators. The concept of Green's function Berry
curvature -- which is frequency dependent -- is introduced. We apply this
notion in a system that contains symmetry-protected nodes in its noninteracting
bandstructure; strong correlations drive the system into a Mott insulating
state, creating contours in frequency-momentum space where the Green's function
vanishes. The Green's function Berry flux of such zeros is found to be
quantized, and is as such direct probe of the system's topology. Our framework
allows for a comprehensive search of strongly correlated topological materials
with Green's function topology.Comment: 38 pages, 13 figures including Supplemental Informatio