TY - JOUR

T1 - Formation scenarios for nonlinear patterns in electroconvection under controlling goldstone modes in magnetic field

AU - Huh, Jong Hoon

AU - Hidaka, Yoshiki

AU - Kai, Shoichi

PY - 1999

Y1 - 1999

N2 - We report novel scenarios for the transitions from a stationary periodic state to spatio-temporal chaos (STC) for electroconvection in homeotropically aligned nematics, in which a constant magnetic field H is applied perpendicularly to an electric field. Above a characteristic frequency fL (in the normal roll regime), when increasing the applied electric field, stationary periodic roll patterns become unstable, and evolve to STC at a certain electric field. For f > fL we find the second stationary periodic roll pattern (i.e., abnormal rolls) at higher electric fields for H > H*, where H* is a characteristic magnetic intensity. At much higher electric field the reentrant stationary periodic rolls evolve to STC again. Reentrant stationary rolls are not observed for H < H*. Below fL (in the oblique roll regime), on the other hand, with increasing the electric field, stationary periodic rolls also become unstable toward STC. In the oblique roll regime, however, we find no reentrant stationary rolls below and above H*. The abnormal roll instability responsible for the reentrant rolls corresponds to a homogeneous azimuthal rotation of the director and plays important role for the novel scenarios. Based on systematic studies, we have determined phase diagrams in the H - ε plane, where ε is a normalized electric voltage.

AB - We report novel scenarios for the transitions from a stationary periodic state to spatio-temporal chaos (STC) for electroconvection in homeotropically aligned nematics, in which a constant magnetic field H is applied perpendicularly to an electric field. Above a characteristic frequency fL (in the normal roll regime), when increasing the applied electric field, stationary periodic roll patterns become unstable, and evolve to STC at a certain electric field. For f > fL we find the second stationary periodic roll pattern (i.e., abnormal rolls) at higher electric fields for H > H*, where H* is a characteristic magnetic intensity. At much higher electric field the reentrant stationary periodic rolls evolve to STC again. Reentrant stationary rolls are not observed for H < H*. Below fL (in the oblique roll regime), on the other hand, with increasing the electric field, stationary periodic rolls also become unstable toward STC. In the oblique roll regime, however, we find no reentrant stationary rolls below and above H*. The abnormal roll instability responsible for the reentrant rolls corresponds to a homogeneous azimuthal rotation of the director and plays important role for the novel scenarios. Based on systematic studies, we have determined phase diagrams in the H - ε plane, where ε is a normalized electric voltage.

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U2 - 10.1143/JPSJ.68.1567

DO - 10.1143/JPSJ.68.1567

M3 - Article

AN - SCOPUS:0033445545

VL - 68

SP - 1567

EP - 1577

JO - Journal of the Physical Society of Japan

JF - Journal of the Physical Society of Japan

SN - 0031-9015

IS - 5

ER -