arXiv subjects

J. van Wezel

Publications and source records attributed to J. van Wezel.

3 recordsLinked to original sources

arXiv2026

$H$-linear magnetoresistance in NbSe$_2$ due to impeded cyclotron motion

Linear magnetoresistance (LMR) is a widespread phenomenon observed in a host of quantum materials ranging from semiconductor nanostructures to quantum critical and strange metals. While multiple scenarios to explain LMR have been proposed, a complete understanding of the phenomenon remains elusive. Indeed, it is highly likely that the origin of LMR depends on the specific electronic state. Here, we report a study of the impact of disorder on the form of the magnetoresistance of the prototypical charge-density-wave (CDW) compound 2$H$-NbSe$_2$. The magnetoresistance is shown to exhibit strong qualitative and quantitative agreement with Boltzmann transport analysis incorporating impeded cyclotron motion (ICM). We identify the source of ICM in 2$H$-NbSe$_2$ as strong scattering sinks where the CDW order connects the high temperature Fermi cylinders. Such unusual "hotspots" provide an explanation for the observed LMR as well as for the long-unexplained absence of quantum oscillations inside the charge ordered state in 2$H$-NbSe$_2$. These findings provide strong evidence that ICM generates LMR in certain correlated metals.

cond-mat.str-el↗

arXiv2018

Orbital selectivity causing anisotropy and particle-hole asymmetry in the charge density wave gap of $2H$-TaS$_2$

We report an in-depth Angle Resolved Photoemission Spectroscopy (ARPES) study on $2H$-TaS$_2$, a canonical incommensurate Charge Density Wave (CDW) system. This study demonstrates that just as in related incommensurate CDW systems, $2H$-TaSe$_2$ and $2H$-NbSe$_2$, the energy gap ($Δ_{\text{cdw}}\,$) of $2H$-TaS$_2$ is localized along the K-centered Fermi surface barrels and is particle-hole asymmetric. The persistence of $Δ_{\text{cdw}}\,$ even at temperatures higher than the CDW transition temperature $\it{T}_{\text{cdw}}\,$ in $2H$-TaS$_2$, reflects the similar pseudogap (PG) behavior observed previously in $2H$-TaSe$_2$ and $2H$-NbSe$_2$. However, in sharp contrast to $2H$-NbSe$_2$, where $Δ_{\text{cdw}}\,$ is non-zero only in the vicinity of a few "hot spots" on the inner K-centered Fermi surface barrels, $Δ_{\text{cdw}}\,$ in $2H$-TaS$_2$ is non-zero along the entirety of both K-centered Fermi surface barrels. Based on a tight-binding model, we attribute this dichotomy in the momentum dependence and the Fermi surface specificity of $Δ_{\text{cdw}}\,$ between otherwise similar CDW compounds to the different orbital orientations of their electronic states that are involved in CDW pairing. Our results suggest that the orbital selectivity plays a critical role in the description of incommensurate CDW materials.

cond-mat.str-el↗

arXiv2015

Emergence of coherence in the charge-density wave state of 2H-NbSe$_2$

A charge-density wave (CDW) state has a broken symmetry described by a complex order parameter with an amplitude and a phase. The conventional view, based on clean, weak-coupling systems, is that a finite amplitude and long-range phase coherence set in simultaneously at the CDW transition temperature T$_{cdw}$. Here we investigate, using photoemission, X-ray scattering and scanning tunneling microscopy, the canonical CDW compound 2H-NbSe$_2$ intercalated with Mn and Co, and show that the conventional view is untenable. We find that, either at high temperature or at large intercalation, CDW order becomes short-ranged with a well-defined amplitude that impacts the electronic dispersion, giving rise to an energy gap. The phase transition at T$_{cdw}$ marks the onset of long-range order with global phase coherence, leading to sharp electronic excitations. Our observations emphasize the importance of phase fluctuations in strongly coupled CDW systems and provide insights into the significance of phase incoherence in `pseudogap' states.

cond-mat.str-el↗