RT Journal Article
SR Electronic
T1 Large discrete jumps observed in the transition between Chern states in a ferromagnetic topological insulator
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP e1600167
DO 10.1126/sciadv.1600167
VO 2
IS 7
A1 Liu, Minhao
A1 Wang, Wudi
A1 Richardella, Anthony R.
A1 Kandala, Abhinav
A1 Li, Jian
A1 Yazdani, Ali
A1 Samarth, Nitin
A1 Ong, N. Phuan
YR 2016
UL http://advances.sciencemag.org/content/2/7/e1600167.abstract
AB A striking prediction in topological insulators is the appearance of the quantized Hall resistance when the surface states are magnetized. The surface Dirac states become gapped everywhere on the surface, but chiral edge states remain on the edges. In an applied current, the edge states produce a quantized Hall resistance that equals the Chern number C = ±1 (in natural units), even in zero magnetic field. This quantum anomalous Hall effect was observed by Chang et al. With reversal of the magnetic field, the system is trapped in a metastable state because of magnetic anisotropy. We investigate how the system escapes the metastable state at low temperatures (10 to 200 mK). When the dissipation (measured by the longitudinal resistance) is ultralow, we find that the system escapes by making a few very rapid transitions, as detected by large jumps in the Hall and longitudinal resistances. Using the field at which the initial jump occurs to estimate the escape rate, we find that raising the temperature strongly suppresses the rate. From a detailed map of the resistance versus gate voltage and temperature, we show that dissipation strongly affects the escape rate. We compare the observations with dissipative quantum tunneling predictions. In the ultralow dissipation regime, two temperature scales (T1 ~ 70 mK and T2 ~ 145 mK) exist, between which jumps can be observed. The jumps display a spatial correlation that extends over a large fraction of the sample.