scholarly journals Spontaneous breaking of time-reversal symmetry in the pseudogap state of a high-Tc superconductor

Nature ◽  
2002 ◽  
Vol 416 (6881) ◽  
pp. 610-613 ◽  
Author(s):  
A. Kaminski ◽  
S. Rosenkranz ◽  
H. M. Fretwell ◽  
J. C. Campuzano ◽  
Z. Li ◽  
...  
Keyword(s):  
Time Reversal ◽  
Spontaneous Breaking ◽  
Time Reversal Symmetry ◽  
High Tc ◽  
Pseudogap State ◽  
High Tc Superconductor

scholarly journals Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd2As2

2019 ◽  
Vol 5 (7) ◽  
pp. eaaw4718 ◽  
Author(s):  
J.-Z. Ma ◽  
S. M. Nie ◽  
C. J. Yi ◽  
J. Jandke ◽  
T. Shang ◽  
...  
Keyword(s):  
Long Range ◽  
Time Reversal ◽  
Spin Fluctuation ◽  
Paramagnetic Phase ◽  
Spontaneous Breaking ◽  
Time Reversal Symmetry ◽  
Energy Bands ◽  
Range Magnetic Order ◽  
Weyl Semimetal ◽  
Long Range Magnetic Order

Weyl fermions as emergent quasiparticles can arise in Weyl semimetals (WSMs) in which the energy bands are nondegenerate, resulting from inversion or time-reversal symmetry breaking. Nevertheless, experimental evidence for magnetically induced WSMs is scarce. Here, using photoemission spectroscopy, we observe that the degeneracy of Bloch bands is already lifted in the paramagnetic phase of EuCd2As2. We attribute this effect to the itinerant electrons experiencing quasi-static and quasi–long-range ferromagnetic fluctuations. Moreover, the spin-nondegenerate band structure harbors a pair of ideal Weyl nodes near the Fermi level. Hence, we show that long-range magnetic order and the spontaneous breaking of time-reversal symmetry are not essential requirements for WSM states in centrosymmetric systems and that WSM states can emerge in a wider range of condensed matter systems than previously thought.

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