High mobility in a van der Waals layered antiferromagnetic metal

Van der Waals (vdW) materials with magnetic order have been heavily pursued for fundamental physics as well as for device design. Despite the rapid advances, so far, they are mainly ...

Uncovering electron-phonon scattering and phonon dynamics in type-I Weyl semimetals

Studies of topological semimetals have revealed spectacular transport phenomena spanning extreme magnetoresistance effects and ultrahigh mobilities. As phonon dynamics and electron-phonon scattering play a critical role in the electrical and ...

Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor

Combining topology and superconductivity providesa powerful tool for investigating fundamental physics as well as aroute to fault-tolerant quantum computing. There is mountingevidence that the Fe-based superconductor FeTe0.55Se0.45 (FTS)may also be topologically ...

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Posted by Kenneth Burch On February - 12 - 2020 0 Comment

Van der Waals (vdW) materials with magnetic order have been heavily pursued for fundamental physics as well as for device design. Despite the rapid advances, so far, they are mainly insulating or semiconducting, and none of them has a high electronic mobility—a property that is rare in layered vdW materials in general. The realization of a high-mobility vdW material that also exhibits magnetic order would open the possibility for novel magnetic twistronic or spintronic devices. Here, we report very high carrier mobility in the layered vdW antiferromagnet GdTe3. The electron mobility is beyond 60,000 cm/Vs , which is the highest  [ Read More ]

Posted by Kenneth Burch On December - 24 - 2019 Comments Off on Uncovering electron-phonon scattering and phonon dynamics in type-I Weyl semimetals

Studies of topological semimetals have revealed spectacular transport phenomena spanning extreme magnetoresistance effects and ultrahigh mobilities. As phonon dynamics and electron-phonon scattering play a critical role in the electrical and thermal transport, we pursue a fundamental understanding of these effects in type-I Weyl semimetals NbAs and TaAs. In the temperature-dependent Raman spectra of NbAs we reveal a previously unreported Fano line shape, a signature stemming from the electron-phonon interaction. Additionally, the temperature dependence of the A1 phonon linewidths in both NbAs and TaAs strongly deviate from the standard model of anharmonic decay. To capture the mechanisms responsible for the observed Fano asymmetry  [ Read More ]

Posted by Kenneth Burch On September - 5 - 2019 Comments Off on Evidence for Helical Hinge Zero Modes in an Fe-Based Superconductor

Combining topology and superconductivity providesa powerful tool for investigating fundamental physics as well as aroute to fault-tolerant quantum computing. There is mountingevidence that the Fe-based superconductor FeTe0.55Se0.45 (FTS)may also be topologically nontrivial. Should the superconductingorder be s±, then FTS could be a higher order topologicalsuperconductor with helical hinge zero modes (HHZMs). To testthe presence of these modes, we have fabricated normal-metal/superconductor junctions on different surfaces via 2D atomic crystalheterostructures. As expected, junctions in contact with the hingereveal a sharp zero bias anomaly that is absent when tunnelingpurely into the c-axis. Additionally, the shape and suppression withtemperature are consistent with highly coherent modes  [ Read More ]

Posted by Kenneth Burch On April - 22 - 2019 Comments Off on Coulomb blockade in an atomically thin quantum dot

Gate-tunable quantum-mechanical tunneling of particles between a quantum confined state and a nearby Fermi reservoir of delocalized states has underpinned many advances in spintronics and solid-state quantum optics. The prototypical example is a semiconductor quantum dot separated from a gated contact by a tunnel barrier. This enables Coulomb blockade, the phenomenon whereby electrons or holes can be loaded one-by-one into a quantum dot. Depending on the tunnel-coupling strength, this capability facilitates single spin quantum bits or coherent many-body interactions between the confined spin and the Fermi reservoir. Van der Waals (vdW) heterostructures, in which a wide range of unique atomic  [ Read More ]

Posted by Kenneth Burch On March - 14 - 2019 Comments Off on Colossal Bulk Photovoltaic Effect in a Type-I Weyl Semimetal

Broadband, efficient and fast conversion of light to electricity is crucial for sensing and clean energy. The bulk photovoltaic effect (BPVE) is a second-order nonlinear optical effect that intrinsically converts light into electrical current. Here, we demonstrate a large mid-infrared BPVE in microscopic devices of the Weyl semimetal TaAs. This discovery results from combining recent developments in Weyl semimetals, focused-ion beam fabrication and theoretical works suggesting a connection between BPVE and topology. We also present a detailed symmetry analysis that allows us to separate the shift current response from photothermal effects. The magnitude and wavelength range of the assigned shift  [ Read More ]