Biography
Biography: Ramesh G Mani
Abstract
The Hall-eff ect remains broadly important nearly 140 years aft er its discovery. In science, the integral and fractional- quantum Hall eff ects have revolutionized condensed matter physics. Meanwhile, the classical Hall-eff ect remains a vital semiconductor characterization tool and proven contactless-sensing technology for essential applications. Recent work, see C. Kern et al., Phys. Rev. Lett. 118, 016601 (2017), claims novel sign reversal of the Hall-coeffi cient in chain-mail-like 3D metamaterials, whereby an n-type semiconductor mimics the Hall-eff ect of a p-type semiconductor, see also Physics Today 70 (2), 21 (2017); Nature 544, 44 (2017). Measurement-geometry-related Hall-eff ect sign-inversion is known from studies of 2D or 3D- semiconductor plates including a hole with current and voltage contacts placed on the interior boundary of the hole (see R. G. Mani et al., Appl. Phys. Lett. 64, 1262 (1994); Z. Phys. B 92, 335 (1993); Patents: DE 4308375C2; U.S. 5,646,527; EP 0689723B1). Studies of such “anti-hall bars” demonstrate a
sign reversed Hall-eff ect with respect to the standard hole-less geometry. A Hall-bar including a single supplementary hole can be transformed into an “anti-hall-bar” by turning the sample inside out, which shift s the exterior boundary and contacts to the sample interior while moving the hole-boundary to the exterior. For a fi xed direction of the magnetic fi eld B, device-inversion leads to signreversal of the Hall-eff ect in “anti-hall bars” since the device-orientation becomes fl ipped with respect to B. Here, we discuss the relation between such sign inversion and the reported sign reversal of the Hall coeffi cient in metamaterials.