Unconventional Magnetism in Layered Transition Metal Dichalcogenides

Abstract

In this contribution to the MDPI Condensed Matter issue in Honor of Nobel Laureate Professor K.A. Müller I review recent experimental progress on magnetism of semiconducting transition metal dichalcogenides (TMDs) from the local-magnetic probe point of view such as muon-spin rotation and discuss prospects for the creation of unique new device concepts with these materials. TMDs are the prominent class of layered materials, that exhibit a vast range of interesting properties including unconventional semiconducting, optical, and transport behavior originating from valley splitting. Until recently, this family has been missing one crucial member: magnetic semiconductor. The situation has changed over the past few years with the discovery of layered semiconducting magnetic crystals, for example CrI 3 and VI 2 . We have also very recently discovered unconventional magnetism in semiconducting Mo-based TMD systems 2H-MoTe 2 and 2H-MoSe 2 [Guguchia et. al., Science Advances 2018, 4(12)]. Moreover, we also show the evidence for the involvement of magnetism in semiconducting tungsten diselenide 2H-WSe 2 . These results open a path to studying the interplay of 2D physics, semiconducting properties and magnetism in TMDs. It also opens up a host of new opportunities to obtain tunable magnetic semiconductors, forming the basis for spintronics.

The Magnetic Genome of Two-Dimensional van der Waals Materials

“…(c) The so-called asymmetry (or μSR) signal is obtained by essentially building the difference between N F and N B ( eq 2 ). All panels are adapted with permission under a Creative Common CC BY license from ref ( 350 ). Copyright 2019 MDPI.…”

“…(d, e) Isotropic Gaussian field distribution for polycrystalline sample. Panels (a–c) adapted with permission under a Creative Common CC BY license from ref ( 350 ). Copyright 2019 MDPI.…”

“… (a) ZF μSR time spectra for the single crystal samples of T d -MoTe 2 and 2H-MoTe 2 recorded at T = 5 K. Adapted with permission under a Creative Common CC BY license from ref ( 350 ). Copyright 2019 MDPI.…”

Local spectroscopic evidence for a nodeless magnetic kagome superconductor CeRu2

“…During a µSR experiment, positive muons are implanted into the sample, where they thermalize at interstitial positions and precess in the local magnetic field. They decay radioactively after a mean lifetime of 2.2 µs and emit a positron e + preferentially along the spin direction [32]. The asymmetry of emitted positrons is detected and this timedependent polarization P(t) of the ensemble may be fitted with a number of different functions, elucidating the physics of the investigated material (see the supplemental material for details).…”

Future facilities at PSI, the High-Intensity Muon Beams (HIMB) project

“…At PSI, the High Intensity Proton Accelerator (HIPA) facility delivers one of the most powerful proton beams to target stations, 1.4 MW, to produce the most intense continuous muon beams in the world, with rates up to few 10 8 µ + /s, granting PSI the lead at the intensity frontier in both particle physics [1] and condensed matter research with muons [2][3][4][5][6][7]. Such high rates are possible by exploiting 'surface muons', which are anti-muons generated by π + decay at rest inside the production target within a very narrow momentum range.…”