arXiv subjects

Thom Ottenbros

Publications and source records attributed to Thom Ottenbros.

3 recordsLinked to original sources

arXiv2026

Magnetothermopower and particle-hole symmetry in a cuprate strange metal

Here, we report magnetothermopower measurements on overdoped (Bi,Pb)2(Sr,La)2CuO6+delta (Bi2201) single crystals in magnetic fields up to 35 T. Whereas the temperature dependence of the zero-field Seebeck coefficient S(T) can be captured using Boltzmann transport theory, the field-dependent response S(H) cannot. Instead, the magnetothermopower contains a large additional contribution whose field and temperature dependence is consistent with the presence of short-range superconducting order well above Tc. Combined with earlier Hall and magnetoresistance results, these data imply that the overdoped cuprate strange metal contains two transport sectors with distinct particle-hole symmetry: a conventional particle-hole-asymmetric Fermi-liquid (FL) contribution governing the Hall effect and the zero-field thermopower, and a nearly particle-hole-symmetric sector dominating the anomalous longitudinal magnetotransport. We formulate a phenomenological real-space model in which disconnected FL islands are embedded in a compensated Dirac liquid of phase-incoherent d-wave Bogoliubov quasiparticles. This picture reconciles conventional zero-field transport with anomalous magnetothermopower and magnetoresistance and offers a concrete framework for thinking about strange metallicity in overdoped cuprates.

cond-mat.supr-con↗

arXiv2024

From orbital to paramagnetic pair breaking in layered superconductor 2H-NbS$_2$

The superconducting transition metal dichalcogenides 2H-NbSe$_2$ and 2H-NbS$_2$ are intensively studied on account of their unique electronic properties such as Ising superconductivity, found in multi- and monolayers, with upper critical fields beyond the Pauli limit. Even in bulk crystals, there are reports of multiband superconductivity and exotic states, such as the Fulde-Ferrell-Larkin-Ovchinnikov phase. In this work, we investigate the superconducting properties of 2H-NbS$_2$ through a detailed high-field mapping of the phase diagram by means of magnetotransport and magnetostriction experiments. We compare the phase diagram between bulk crystals and a 6~nm thick flake of 2H-NbS$_2$ and find a drastically enhanced Maki parameter in the flake, signifying a change of the relevant pair breaking mechanism from orbital to paramagnetic pair breaking, which we attribute to an effect of enhanced spin-orbit coupling.

cond-mat.supr-con↗

arXiv2021

Insulator-to-Metal Crossover near the Edge of the Superconducting Dome in Nd$_{1-x}$Sr$_x$NiO$_2$

We report a systematic magnetotransport study of superconducting infinite-layer nickelate thin films Nd$_{1-x}$Sr$_x$NiO$_2$ with $0.15 \leq x \leq 0.225$. By suppressing superconductivity with out-of-plane magnetic fields up to 37.5 T, we find that the normal state resistivity of Nd$_{1-x}$Sr$_x$NiO$_2$ is characterized by a crossover from a metallic $T^2$-behavior to an insulating log(1/$T$)-behavior for all $x$ except $x = 0.225$, at which the resistivity is predominantly metallic. The log(1/$T$)-behavior is found to be robust against magnetic fields, inconsistent with scenarios involving localization or Kondo scattering, and points to an anomalous insulating state possibly driven by strong correlations. In the metallic state, we find no evidence for non-Fermi-liquid behavior arising from proximity to a putative quantum critical point located inside the superconducting dome.

cond-mat.supr-con↗