Two energy gaps and Fermi-surface "arcs" in NbSe2.
Using angle-resolved photoemission spectroscopy, we report on the direct observation of the energy gap in 2H-NbSe2 caused by the charge-density waves (CDW). The gap opens in the regions of the momentum space connected by the CDW vectors, which implies a nesting mechanism of CDW formation. In remarkable analogy with the pseudogap in cuprates, the detected energy gap also exists in the normal state (T>T0) where it breaks the Fermi surface into "arcs," it is nonmonotonic as a function of temperature with a local minimum at the CDW transition temperature (T0), and it forestalls the superconducting gap by excluding the nested portions of the Fermi surface from participating in superconductivity.
Borisenko
S V
SV
Leibniz-Institute for Solid State Research, IFW-Dresden, D-01171, Dresden, Germany.
Kordyuk
A A
AA
Zabolotnyy
V B
VB
Inosov
D S
DS
Evtushinsky
D
D
Büchner
B
B
Yaresko
A N
AN
Varykhalov
A
A
Follath
R
R
Eberhardt
W
W
Patthey
L
L
Berger
H
H