Today, surface acoustic waves (SAWs) and bulk acoustic waves are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applications in life sciences and microfluidics for sensing and mixing of tiny amounts of liquids. In addition to this continuously growing number of applications, SAWs are ideally suited to probe and control elementary excitations in condensed matter at the limit of single quantum excitations. Even collective excitations, classical or quantum are nowadays coherently interfaced by SAWs. This wide, highly diverse, interdisciplinary and continuously expanding spectrum literally unites advanced sensing and manipulation applications. Remarkably, SAW technology is inherently multiscale and spans from single atomic or nanoscopic units up even to the millimeter scale. The aim of this Roadmap is to present a snapshot of the present state of surface acoustic wave science and technology in 2019 and provide an opinion on the challenges and opportunities that the future holds from a group of renown experts, covering the interdisciplinary key areas, ranging from fundamental quantum effects to practical applications of acoustic devices in life science.

The acoustoelectric effect in a hybrid of a strong piezoelectric material and a semiconductor layer containing a two-dimensional electron system is investigated. Caused by the very strong interaction between a surface acoustic wave and the mobile carriers in the semiconductor, the acoustoelectric effect is very large as compared to other materials, which might be interesting for device applications. Moreover, the tunability of the sheet conductivity of the electron system enables us to tune the magnitude of the acoustoelectric effect over a wide range. We present experimental results for a GaAs/LiNbO3 layered hybrid system at room temperature and describe our experimental findings quantitatively using a recently developed model calculation.

The combination of semiconductor quantum well structures and strongly piezoelectric crystals leads to a system in which surface acoustic waves with very large amplitudes can interact with charge carriers in the well. The surface acoustic wave induces a dynamic lateral superlattice potential in the plane of the quantum well which is strong enough to spatially break up a two-dimensional electron system into moving wires of trapped charge. This transition is manifested in an increase of the electron transport velocity with sound amplitude, eventually reaching the sound velocity. The sound absorption by the electron system then becomes governed by nonlinearities and is strongly reduced. We study the transition from the linear towards the strongly nonlinear regime of interaction and present a theoretical description of such phenomena in a 2D system. [S0031-9007(99)08621-4] PACS numbers: 73.50. Rb, 72.50. + b, 73.50.Fq Electron transport in semiconductor quantum well structures is usually governed by drift or diffusive current flow. Also ballistic carrier motion can be observed, provided that the size of the system is smaller than the mean-free path, ranging up to some hundred microns in very pure semiconductor material. Conceptually different from those mechanisms are transport phenomena based on momentum transfer from externally propagating entities to the electron system. Such "dragging" experiments have been studied in great detail in double electron layer systems [1], where internal "Coulomb friction" between the two layers causes the dragging force. "Photon drag" induced transport was observed for intersubband transitions of a quasi-two-dimensional electron system (2DES) [2]. Nagamune et al. [3] observed the effect of a dc current on the drift of optically generated carriers in a quantum well. Acoustic charge transport (ACT) has been investigated on a variety of different systems in view of possible device applications [4]. Using surface acoustic waves (SAW), Rocke et al. [5] showed that photogenerated electron-hole pairs in a semiconductor quantum well can be efficiently trapped in the moving lateral potential of the sound wave and then be reassembled into photonic signals. Recently, SAW have been combined with Coulomb blockade to drive single electrons through a quantum point contact [6]. In addition, the interaction between SAW and mobile charges in semiconductor layered structures has become an important method to study the dynamic conductivity of low-dimensional systems in quantum wells. These studies include the integer quantum Hall effect [7], the fractional quantum Hall effect [8], Fermi surfaces of composite Fermions around a half-filled Landau level [9], and commensurability effects caused by the lateral superlattice induced by a SAW [10]. These studies, however, were restricted to the small signal limit, i.e., to a regime where the presence of the lateral potential of a piezoelectric wave does not significantly modulate the carrier density in the quantum well.Here, we would like to report on experim...

Independent dynamic acousto-mechanical and electrostatic control of individual quantum dots in a LiNbO 3 -GaAs hybrid

Abslract -Surface acoustic wave devices for identification systems (SAW-ID-tags or SAW wireless labels) have a large potential for future applications. We concentrate in this paper on reflective SAW-IDtags with amplitude modulation.We use splitfinger interdigital transducers as reflecting structures. If the transducers are short circuited or capacitivly loaded the reflection disappears almost entirely. On the other hand, if an open circuit or inductive load is used, the lDTs reflect incoming SAWS. The coding of the reflectors can therefore be done once and for all by a, e.g., photolithographic process or, alternatively, programmable by external circuitry. This new possibility of dynamic programming can be used to transmit time dependent data.We present basic considerations on the design and measurements of prototypes of SAW-ID-tags on YZ-LiNbOS at 285MHz and 2.45GHz.1051-0117/93/0000-0125 $4.00 0 1993 IEEE