Magnetic field tuning of an excitonic insulator between the weak and strong
coupling regimes in quantum limit graphite
#MMPMID28496192
Zhu Z
; McDonald RD
; Shekhter A
; Ramshaw BJ
; Modic KA
; Balakirev FF
; Harrison N
Sci Rep
2017[May]; 7
(1
): 1733
PMID28496192
show ga
The excitonic insulator phase has long been predicted to form in proximity to a
band gap opening in the underlying band structure. The character of the pairing
is conjectured to crossover from weak (BCS-like) to strong coupling (BEC-like) as
the underlying band structure is tuned from the metallic to the insulating side
of the gap opening. Here we report the high-magnetic field phase diagram of
graphite to exhibit just such a crossover. By way of comprehensive angle-resolved
magnetoresistance measurements, we demonstrate that the underlying band gap
opening occurs inside the magnetic field-induced phase, paving the way for a
systematic study of the BCS-BEC-like crossover by means of conventional condensed
matter probes.