Experimental observation of topological Fermi arcs in type-II Weyl semimetal MoTe2 (1603.08508v2)

Abstract: Weyl semimetal is a new quantum state of matter [1-12] hosting the condensed matter physics counterpart of relativisticWeyl fermion [13] originally introduced in high energy physics. The Weyl semimetal realized in the TaAs class features multiple Fermi arcs arising from topological surface states [10, 11, 14-16] and exhibits novel quantum phenomena, e.g., chiral anomaly induced negative mag-netoresistance [17-19] and possibly emergent supersymmetry [20]. Recently it was proposed theoretically that a new type (type-II) of Weyl fermion [21], which does not have counterpart in high energy physics due to the breaking of Lorentz invariance, can emerge as topologically-protected touching between electron and hole pockets. Here, we report direct spectroscopic evidence of topological Fermi arcs in the predicted type-II Weyl semimetal MoTe2 [22-24]. The topological surface states are confirmed by directly observing the surface states using bulk-and surface-sensitive angle-resolved photoemission spectroscopy (ARPES), and the quasi-particle interference (QPI) pattern between the two putative Fermi arcs in scanning tunneling microscopy (STM). Our work establishes MoTe2 as the first experimental realization of type-II Weyl semimetal, and opens up new opportunities for probing novel phenomena such as exotic magneto-transport [21] in type-II Weyl semimetals.

• The paper demonstrates the experimental detection of Fermi arcs in MoTe2, providing direct evidence for its type-II Weyl semimetal nature.
• It employs surface-sensitive ARPES and STM techniques to visualize surface states and analyze quasi-particle interference consistent with theoretical predictions.
• The findings pave the way for exploring novel quantum phenomena and potential applications in advanced electronic and spintronic devices.

Topological Fermi Arcs in Type-II Weyl Semimetal MoTe$_2$

The paper "Experimental observation of topological Fermi arcs in type-II Weyl semimetal MoTe$_2$" presents a substantial advancement in condensed matter physics by providing experimental confirmation of topological Fermi arcs in a type-II Weyl semimetal. Weyl semimetals represent a class of quantum materials hosting Weyl fermions, which feature distinct electronic states known as Fermi arcs. MoTe$_2$ is purported to be a type-II Weyl semimetal, where the Weyl fermions emerge due to broken Lorentz invariance and exist at the boundary between electron and hole pockets in the momentum space.

Summary of Experimental Findings

The authors employed surface-sensitive angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM) to detect and map the topological surface states predicted in MoTe$_2$. The ARPES measurements, using both UV and laser sources, enabled the visualization of surface states in the bulk and surface Brillouin zones. These states were shown to form the characteristic Fermi arcs connecting Weyl points of opposite chirality, serving as experimental evidence for theoretical predictions about the band structure of type-II Weyl semimetals.

STM was utilized to further substantiate the surface nature of the observed Fermi arcs by examining the quasi-particle interference (QPI) patterns. The observed QPI features are consistent with the scattering vectors expected from the topology of the Fermi arcs, reinforcing the ARPES findings.

Numerical and Theoretical Implications

A critical aspect of this paper is the calculation-intensive approach used to predict the electronic structure of MoTe$_2$. The calculations, performed to correspond with both the inversion-symmetric and asymmetric phases of MoTe$_2$, delineated the presence of electronic pockets and topological Fermi arcs at specific energies. The alignment between these calculations and the experimental results signifies the robust predictability of theoretical models employed for type-II Weyl semimetals.

Implications and Future Directions

The experimental visualization of topological Fermi arcs in MoTe$_2$ holds significant implications for understanding the transport properties of Weyl semimetals. The existence and characteristics of these arcs could lead to novel quantum phenomena, such as exotic magnetoresistance behaviors, which could be exploited for next-generation electronic devices. In the broader context, this work underlines the potential of type-II Weyl semimetals to open up new directions in both applied physics and further theoretical exploration of topological phases.

Given the successful experimental establishment of MoTe$_2$ as a type-II Weyl semimetal, future research could explore exploring other materials with similar properties, observing the effects of external perturbations such as strain or electromagnetic fields on the topological states, and integrating this knowledge toward practical implementations in quantum computing and advanced material science.