Spin-Resolved Electronic Response to the Phase Transition in MoTe2

Abstract

The semimetal MoTe2 is studied by spin-and angle-resolved photoemission spectroscopy to probe the detailed electronic structure underlying its broad range of response behavior. A novel spin-texture is uncovered in the bulk Fermi surface of the non-centrosymmetric structural phase that is consistent with first-principles calculations. The spin-texture is three-dimensional, both in terms of momentum dependence and spin-orientation, and is not completely suppressed above the centrosymmetry-breaking transition temperature. Two types of surface Fermi arc are found to persist well above the transition temperature. The appearance of a large Fermi arc depends strongly on thermal history, and the electron quasiparticle lifetimes are greatly enhanced in the initial cooling. The results indicate that polar instability with strong electron-lattice interactions exists near the surface when the bulk is largely in a centrosymmetric phase.

Spin- and angle-resolved photoemission on topological materials

“…Furthermore, a careful measurement of the spin texture ( Fig. 12) and quasiparticle life time in MoTe 2 through the phase transition to a centrosymmetric system (T d to 1T ′ ) it could be determined that new form of polar instability exists near the surface 124 .…”

Appearance of a Td* phase across the Td−1T′ phase boundary in the Weyl semimetal Yu1, Schneeloch2, Duan3 et al. 2019Phys. Rev. B

“…Structural distortions have been known to occur, such as stacking disorder during the phase transition, evidenced by the presence of diffuse scattering observed in neutron [8] and X-ray [9] experiments, and hysteresis effects that extend far beyond the transition region, as seen in resistivity measurements along the thermal hysteresis loop [10]. These effects have been largely ignored, though one of the surface Fermi arcs was noted to persist to ∼90 K above the transition temperature and to have a history-dependent appearance [6]. In general, structural phase transitions that involve in-plane translations of layers resulting from changes in temperature or pressure have been neglected, but many materials fall in this category, including Ta 2 NiSe 5 [11], In 2 Se 3 [12,13], α-RuCl 3 [14], CrX 3 (X=Cl, Br, I) [15], and MoS 2 [16][17][18].…”

Direct observation of hidden spin polarization in 2H−MoTe2

“…Spin splitting [19][20][21][22] has been observed in the K valley of inversion asymmetric TMDC structures that are interlocked [14,23,24] with the coexisted valley polarization effect [16][17][18]. Whereas in the centrosymmetric TMDC structures, a new type of spin effect, i.e., the hidden spin polarization [5], also known as layer-locked hidden spin texture in layered materials [3], has been observed [4,[25][26][27][28]. Although it is well established that the optical properties of inversion symmetric TMDC systems [29][30][31] are qualitatively affected by their hidden spin texture, a concern that the observed hidden spin texture [4,[25][26][27][28] might be mainly induced by the broken inversion symmetry in experiments was raised recently [32].…”

“…Whereas in the centrosymmetric TMDC structures, a new type of spin effect, i.e., the hidden spin polarization [5], also known as layer-locked hidden spin texture in layered materials [3], has been observed [4,[25][26][27][28]. Although it is well established that the optical properties of inversion symmetric TMDC systems [29][30][31] are qualitatively affected by their hidden spin texture, a concern that the observed hidden spin texture [4,[25][26][27][28] might be mainly induced by the broken inversion symmetry in experiments was raised recently [32]. Therefore it is critical to perform combined experimental and theoretical studies on centrosymmetric TMDC materials such as 2H-MoTe 2 to explore the mechanism of the hidden spin polarization [5].…”

“…MoTe 2 possesses intriguing physical properties, including type-II topological Weyl semimetal phase [33], spin splitting [28], and valleytronics [34]. It can be stabilized near room temperature in three types of crystal structures, namely, the 2H (hexagonal) [35], 1T (monoclinic) [36], and T d (orthorhombic) [33] phases.…”