6,182 research outputs found
Local Flattening of the Fermi Surface and Quantum Oscillations in the Magnetoacoustic Response of a Metal
In the present work we theoretically analyze the effect of the Fermi surface
local geometry on quantum oscillations in the velocity of an acoustic wave
travelling in metal across a strong magnetic field. We show that local
flattenings of the Fermi surface could cause significant amplification of
quantum oscillations. This occurs due to enhancement of commensurability
oscillations modulating the quantum oscillations in the electron density of
states on the Fermi surface. The amplification in the quantum oscillations
could be revealed at fitting directions of the magnetic field.Comment: 4 pages, 1 figure, text adde
Large magnetoresistance in type-II Weyl semimetal WP
We report magnetotransport study on type-II Weyl semimetal WP single
crystals. Magnetoresistance (MR) exhibits a nonsaturating field
dependence (14,300\% at 2 K and 9 T) whereas systematic violation of Kohler's
rule was observed. Quantum oscillations reveal a complex multiband electronic
structure. The cyclotron effective mass close to the mass of free electron
m was observed in quantum oscillations along -axis, while reduced
effective mass of about 0.5 was observed in -axis quantum oscillations,
suggesting Fermi surface anisotropy. Temperature dependence of the resistivity
shows a large upturn that cannot be explained by the multi-band
magnetoresistance of conventional metals. Even though crystal structure of
WP is not layered as in transition metal dichalcogenides, quantum
oscillations suggest partial two-dimensional character.Comment: Accepted by PR
Modification of the Lifshitz-Kosevich formula for anomalous quantum oscillations in inverted insulators
It is generally believed that quantum oscillations are a hallmark of a Fermi
surface and the oscillations constitute the ringing of it. Recently, it was
understood that in order to have well defined quantum oscillations you do not
only not need well defined quasiparticles, but also the presence of a Fermi
surface is unnecessary. In this paper we investigate such a situation for an
inverted insulator from a analytical point of view. Even in the insulating
phase clear signatures of quantum oscillations are observable and we give a
fully analytical formula for the strongly modified Lifshitz-Kosevich amplitude
which applies in the clean as well as the disordered case at finite
temperatures.Comment: 8 figure
Quantum oscillations from Fermi arcs
When a metal is subjected to strong magnetic field B nearly all measurable
quantities exhibit oscillations periodic in 1/B. Such quantum oscillations
represent a canonical probe of the defining aspect of a metal, its Fermi
surface (FS). In this study we establish a new mechanism for quantum
oscillations which requires only finite segments of a FS to exist. Oscillations
periodic in 1/B occur if the FS segments are terminated by a pairing gap. Our
results reconcile the recent breakthrough experiments showing quantum
oscillations in a cuprate superconductor YBCO, with a well-established result
of many angle resolved photoemission (ARPES) studies which consistently
indicate "Fermi arcs" -- truncated segments of a Fermi surface -- in the normal
state of the cuprates.Comment: 8 pages, 5 figure
Quantum oscillations in topological superconductor candidate CuBiSe
Quantum oscillations are generally studied to resolve the electronic
structure of topological insulators. In CuBiSe, the prime
candidate of topological superconductors, quantum oscillations are still not
observed in magnetotransport measurement. However, using torque magnetometry,
quantum oscillations (the de Hass - van Alphen effect) were observed in
CuBiSe . The doping of Cu in BiSe increases the
carrier density and the effective mass without increasing the scattering rate
or decreasing the mean free path. In addition, the Fermi velocity remains the
same in CuBiSe as that in BiSe. Our results imply that
the insertion of Cu does not change the band structure of BiSe.Comment: 5 pages, 4 figure
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