CoTe₂: A Quantum Critical Dirac Metal with Strong Spin Fluctuations

Abstract

Quantum critical points separating weak ferromagnetic and paramagnetic phases trigger many novel phenomena. Dynamical spin fluctuations not only suppress the long‐range order, but can also lead to unusual transport and even superconductivity. Combining quantum criticality with topological electronic properties presents a rare and unique opportunity. Here, by means of ab initio calculations and magnetic, thermal, and transport measurements, it is shown that the orthorhombic CoTe2 is close to ferromagnetism, which appears suppressed by spin fluctuations. Calculations and transport measurements reveal nodal Dirac lines, making it a rare combination of proximity to quantum criticality and Dirac topology.

General synthesis of magnetic binary transition metal telluride nanocrystals

“…43,44 Notably, the CoTe nanoplates showed a tendency to be saturated in a high field range at 5 K, with an H C value of 650 Oe. 45,46 Furthermore, Ni 0.75 Te and Ni 0.64 Te closely resemble the magnetic behavior of NiTe 2 . Co 0.83 Te displays a similar paramagnetism to CoTe 2 (Fig.…”

Thickness dependent tribological and magnetic behavior of two-dimensional cobalt telluride (CoTe2)

“…According to figure 5(d), it is anticipated that the full-width half maximum of the first derivative for 2D CoTe 2 has a broader distribution of magnetic moments and hence exhibits better magnetization with respect to a given field than the bulk counterpart, which exhibits a weaker magnetization, as shown in the fitted curve. The previous work on bulk CoTe 2 reported its ferromagnetic behavior being suppressed due to strong spin fluctuations, thereby maintaining its paramagnetic nature [60]. The current work is the first paper on magnetic and mechanical properties correlation of 2D CoTe 2 .…”

Emerging 2D Cobalt Telluride (CoxTey): from Theory to Applications

“…Quantum criticality that separates weak ferromagnetic and paramagnetic phases is one of the hot topics in condense matter physics, because it contributes to potential quantum anomalous Hall effect, tunable Weyl points and non‐trivial spin texture that interplays of real and momentum space topography. [ 24,99 ] However, quantum critical materials with a substantial presence of topologically nontrivial states at the Fermi level is rare, constraining the investigations of band crossing and other electronic features. Recently, single‐crystal CoTe 2 was found as a quantum critical Dirac metal with Dirac points and multiple nodal lines at the Fermi surface.…”

“…Without a long‐range ordering and inverse susceptibility, in accordance to the Curie‐Weiss law, the authors concluded that the absence of ordering suggests strong spin fluctuation rather than spin‐orbital coupling. [ 99 ] With further manipulation by doping or pressure, the quantum critical point may enable new physic phenomena, such as Dirac dispersion and topological fermions.…”

“…a‐c) ref Reproduced with permission. [ 99 ] Copyright 2023, John Wiley & Sons, Inc. d) Illustration of CoTe 2 detector coupled with metal antenna. e) The proposed skew scattering and side jump of topological CoTe 2 surface states.…”