Leslie M. Schoop

Large, non-saturating magnetoresistance in WTe2

Magnetoresistance is the change in a material’s electrical resistance in response to an applied magnetic field. Materials with large magnetoresistance have found use as magnetic sensors, in magnetic memory, and in hard drives at room temperature, and their rarity has motivated many fundamental studies in materials physics at low temperatures. Here we report the observation of an extremely large positive magnetoresistance at low temperatures in the non-magnetic layered transition-metal dichalcogenide WTe2: 452,700 per cent at 4.5 kelvins in a magnetic field of 14.7 teslas, and 13 million per cent at 0.53 kelvins in a magnetic field of 60 teslas. In contrast with other materials, there is no saturation of the magnetoresistance value even at very high applied fields. Determination of the origin and consequences of this effect, and the fabrication of thin films, nanostructures and devices based on the extremely large positive magnetoresistance of WTe2, will represent a significant new direction in the study of magnetoresistivity.Magnetoresistance is the change of a material’s electrical resistance in response to an applied magnetic field. In addition to its intrinsic scientific interest, it is a technologically important property, placing it in “Pasteur’s quadrant” of res earch value: materials with large magnetorsistance have found use as magnetic sensors 1, in magnetic memory2, hard drives3, transistors4, and are the subject of frequent study in the field of spintronics5, 6. Here we report the observation of an extremely large one-dimensional posi tive magnetoresistance (XMR) in the layered transition metal dichalcogenide (TMD) WTe2; 452,700% at 4.5 Kelvin in a magnetic field of 14.7 Tesla, and 2.5 million% at 0.4 Kelvin in 45 Tesla, with no saturation. The XMR is highly anisotropic, maximized in the crystallographic direction where small pockets of holes and electrons are found in the electronic structure . The determination of the origin of this effect and the fabrication of nanostructures and devices based on the XMR of WTe2 will represent a significant new direction in the study and uses of magnetoresistivity.

Dirac cone protected by non-symmorphic symmetry and three-dimensional Dirac line node in ZrSiS

Materials harbouring exotic quasiparticles, such as massless Dirac and Weyl fermions, have garnered much attention from physics and material science communities due to their exceptional physical properties such as ultra-high mobility and extremely large magnetoresistances. Here, we show that the highly stable, non-toxic and earth-abundant material, ZrSiS, has an electronic band structure that hosts several Dirac cones that form a Fermi surface with a diamond-shaped line of Dirac nodes. We also show that the square Si lattice in ZrSiS is an excellent template for realizing new types of two-dimensional Dirac cones recently predicted by Young and Kane. Finally, we find that the energy range of the linearly dispersed bands is as high as 2 eV above and below the Fermi level; much larger than of other known Dirac materials. This makes ZrSiS a very promising candidate to study Dirac electrons, as well as the properties of lines of Dirac nodes.

Three-dimensional Dirac semimetals: Design principles and predictions of new materials

Design principles and novel predictions of new 3D Dirac semimetals are presented, along with the context of currently known materials. Current materials include those based on a topological to trivial phase transition, such as in TlBiSe

Butterfly magnetoresistance, quasi-2D Dirac Fermi surface and topological phase transition in ZrSiS

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A new form of Ca3P2 with a ring of Dirac nodes

S

Topological semimetal in a Bi-Bi2Se3 infinitely adaptive superlattice phase

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Correlation of crystal quality and extreme magnetoresistance of WTe2

and Hg

A ferromagnetic insulating substrate for the epitaxial growth of topological insulators

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Dirac line nodes and effect of spin-orbit coupling in the nonsymmorphic critical semimetals MSiS (M = Hf, Zr)

Cd

Non-symmorphic band degeneracy at the Fermi level in ZrSiTe

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