Session D04: AMO II

Probing optoelectronics and energy conversion at the molecular scale

Molecules are the fundamental building blocks of materials. Creating functional optoelectronic devices at the molecular scale and understanding the underlying physics and chemistry is essential for the development of smaller, faster, and more eco-friendly nanotechnologies for applications in optoelectronics, energy conversion, and chemical / bio-sensing. In this talk, I will introduce our research in developing single-molecule experimental tools and discuss how these tools enabled us to address challenges in probing and controlling quantum transport and energy transport in molecular junction devices. First, I will begin by showing how a DNA molecular diode can be experimentally created.^[1] Second, I will introduce the direct observation of the thermoelectric cooling effect in molecular junctions.^[2] Last, I will present how single molecules can be employed as nanosensors for plasmonic hot carriers.^[3]

    

Bragg Interferometer Gyroscope in a Time-Orbiting Potential

Precision rotation sensing is useful for navigation, geophysics, and tests of fundamental physics. Atom interferometers provide, by some measures, the most sensitive method for rotation sensing achieved to date. However, the best performance requires freely falling atoms in a large experimental apparatus. Many applications, such as navigating a vehicle, will benefit from a more compact geometry. One method to achieve this is by using trapped atoms that are suspended against gravity. We have implemented such an interferometer and used it to measure a rotation rate comparable to that of the Earth. The most recent iteration of the interferometer has demonstrated improvements by a factor of ten in rotation sensitivity and trap stability, with a net enclosed area of 8 mm² for rubidium atoms. We have also implemented a compact version of the apparatus using a novel atom chip design.

    

Double-target BEC atomtronic rotation sensor

We describe an idea for an atomtronic rotation sensor consisting of a rectangular array of pairs of target–Bose-Einstein condensates (BECs). A target BEC is a condensate confined in the "target” trap which is a 2D channel potential consisting of a central well surrounded by a ring–shaped channel. A condensate formed in such a potential will have a central disk condensate inside of a concentric ring–shaped condensate. We assume that the rest frame of the target–BEC–pair array is rotating at some speed, Ω_R , with respect to a frame at rest with respect to the “fixed stars”. The purpose of the sensor described here is to measure Ω_R .  We show that a single target-pair BEC having circulation in one of the rings will undergo circulation transfer when a barrier potential is turned on where the rings overlap.  If Ω_R > Ω_c , where Ω_c is some rotating-frame speed threshold, and that no transfer occurs if Ω_R < Ω_c. It is also the case that Ω_c depends on U_b,max , the maximum barrier strength.  Thus an array of such target-pair BECs, where barriers of different maximum strengths are applied, can bound the value of Ω_R .  We have simulated such a system for different rotation speeds and locations of the array relative to the location of the rotation axis.  We will discuss the potential perfomance of such systems and the possible ranges of Ω_R that could be measured.