93 research outputs found
Signatures of a magnetic-field-induced Lifshitz transition in the ultra-quantum limit of the topological semimetal ZrTe5
The quantum limit (QL) of an electron liquid, realised at strong magnetic fields, has long been proposed to host a wealth of strongly correlated states of matter. Electronic states in the QL are, for example, quasi-one dimensional (1D), which implies perfectly nested Fermi surfaces prone to instabilities. Whereas the QL typically requires unreachably strong magnetic fields, the topological semimetal ZrTe5 has been shown to reach the QL at fields of only a few Tesla. Here, we characterize the QL of ZrTe5 at fields up to 64 T by a combination of electrical-transport and ultrasound measurements. We find that the Zeeman effect in ZrTe5 enables an efficient tuning of the 1D Landau band structure with magnetic field. This results in a Lifshitz transition to a 1D Weyl regime in which perfect charge neutrality can be achieved. Since no instability-driven phase transitions destabilise the 1D electron liquid for the investigated field strengths and temperatures, our analysis establishes ZrTe5 as a thoroughly understood platform for potentially inducing more exotic interaction-driven phases at lower temperatures
Recommended from our members
Unconventional Hall response in the quantum limit of HfTe5
Interacting electrons confined to their lowest Landau level in a high magnetic field can form a variety of correlated states, some of which manifest themselves in a Hall effect. Although such states have been predicted to occur in three-dimensional semimetals, a corresponding Hall response has not yet been experimentally observed. Here, we report the observation of an unconventional Hall response in the quantum limit of the bulk semimetal HfTe5, adjacent to the three-dimensional quantum Hall effect of a single electron band at low magnetic fields. The additional plateau-like feature in the Hall conductivity of the lowest Landau level is accompanied by a Shubnikov-de Haas minimum in the longitudinal electrical resistivity and its magnitude relates as 3/5 to the height of the last plateau of the three-dimensional quantum Hall effect. Our findings are consistent with strong electron-electron interactions, stabilizing an unconventional variant of the Hall effect in a three-dimensional material in the quantum limit
Observation of a three-dimensional fractional Hall response in HfTe5
Interacting electrons in two dimensions can bind magnetic flux lines to form
composite quasiparticles with fractional electric charge, manifesting
themselves in the fractional quantum Hall effect (FQHE). Although the FQHE has
also been predicted to occur in three dimensions, it has not yet been
experimentally observed. Here, we report the observation of fractional plateaus
in the Hall conductivity of the bulk semimetal HfTe5 at magnetic fields beyond
the quantum limit. The plateaus are accompanied by Shubnikov-de Haas minima of
the longitudinal electrical resistivity. The height of the Hall plateaus is
given by twice the Fermi wave vector in the direction of the applied magnetic
field and scales with integer and particular fractional multiples of the
conductance quantum. Our findings are consistent with strong electron-electron
interactions, stabilizing a fractionalized variant of the Hall effect in three
dimensions.Comment: 35 pages with 17 figure
Giant quantum oscillations in thermal transport in low-density metals via electron absorption of phonons
Oscillations of conductance observed in strong magnetic fields are a striking
manifestation of the quantum dynamics of charge carriers in solids. The large
charge carrier density in typical metals sets the scale of oscillations in both
electrical and thermal conductivity, which characterize the Fermi surface. In
semimetals, thermal transport at low-charge carrier density is expected to be
phonon dominated, yet several experiments observe giant quantum oscillations in
thermal transport. This raises the question of whether there is an overarching
mechanism leading to sizable oscillations that survives in phonon-dominated
semimetals. In this work, we show that such a mechanism exists. It relies on
the peculiar phase-space allowed for phonon scattering by electrons when only a
few Landau levels are filled. Our measurements on the Dirac semimetal ZrTe5
support this counter-intuitive mechanism through observation of pronounced
thermal quantum oscillations, since they occur in similar magnitude and phase
in directions parallel and transverse to the magnetic field. Our phase-space
argument applies to all low-density semimetals, topological or not, including
graphene and bismuth. Our work illustrates that phonon absorption can be
leveraged to reveal degrees of freedom through their imprint on longitudinal
thermal transport
Anomalous Shubnikov-de Haas effect and observation of the Bloch-Gr\"uneisen temperature in the Dirac semimetal ZrTe5
Appearance of quantum oscillations (QO) in both thermodynamic and transport
properties of metals at low temperatures is the most striking experimental
consequence of the existence of a Fermi surface (FS). The frequency of these
oscillations and the temperature dependence of their amplitude provides
essential information about the FS topology and fermionic quasiparticle
properties. Here, we report the observation of an anomalous suppression of the
QO amplitude seen in resistivity (Shubnikov de-Haas effect) at sub-kelvin
temperatures in ZrTe5 samples with a single small FS sheet comprising less than
5% of the first Brillouin zone. By comparing these results with measurements of
the magneto-acoustic QO and the recovery of the usual Lifshitz-Kosevich
behavior of the Shubnikov de-Haas (SdH) effect in ZrTe samples with a
multi-sheet FS, we show that the suppression of the SdH effect originates from
a decoupling of the electron liquid from the lattice. On crossing the so-called
Bloch-Gr\"uneisen temperature, T, electron-phonon scattering becomes
strongly suppressed and in the absence of Umklapp scattering the electronic
liquid regains Galilean invariance. In addition, we show, using a combination
of zero-field electrical conductivity and ultrasonic-absorption measurements,
that entering this regime leads to an abrupt increase of electronic viscosity
Tensile Deformation of Oriented Poly(ε-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)
The structural evolution of micromolded poly(ε-caprolactone)
(PCL) and its miscible blends with noncrystallizable poly(vinyl
methyl ether) (PVME) at the nanoscale was investigated as a function of
deformation ratio and blend composition using in situ synchrotron smallangle
X-ray scattering (SAXS) and scanning SAXS techniques. It was
found that the deformation mechanism of the oriented samples shows a
general scheme for the process of tensile deformation: crystal block slips
within the lamellae occur at small deformations followed by a stressinduced
fragmentation and recrystallization process along the drawing
direction at a critical strain where the average thickness of the crystalline
lamellae remains essentially constant during stretching. The value of the
critical strain depends on the amount of the amorphous component
incorporated in the blends, which could be traced back to the lower
modulus of the entangled amorphous phase and, therefore, the reduced network stress acting on the crystallites upon addition of
PVME. When stretching beyond the critical strain the slippage of the fibrils (stacks of newly formed lamellae) past each other
takes place resulting in a relaxation of stretched interlamellar amorphous chains. Because of deformation-induced introduction of
the amorphous PVME into the interfibrillar regions in the highly oriented blends, the interactions between fibrils becomes
stronger upon further deformation and thus impeding sliding of the fibrils to some extent leading finally to less contraction of the
interlamellar amorphous layers compared to the pure PCLNational Natural Science Foundation of China (21204088 and 21134006). This
work is within the framework of the RCUK/EPSRC Science Bridges China project of UK−China Advanced Materials Research Institute (AMRI)
- …