A paper by Martin Wegener was published in the journal Nature Communications

Acoustic waves in gases, liquids and solids usually exhibit an almost constant speed of sound. An excep­tion are rotons: Rotons are among the quasi­par­ti­cles, which means they behave similarly to free parti­cles. Unlike ordinary acoustic waves in gases, liquids and solids, their sound veloc­ity changes signif­i­cantly with wavelength, even backward travel­ing waves are possible.

Under­stand­ing and using quasi­par­ti­cles like rotons is one of the great challenges of quantum physics. Until now, rotons could only be observed under special quantum physi­cal condi­tions at very low temper­a­tures – thus preclud­ing techni­cal use.

In the article "Roton-like acousti­cal disper­sion relations in 3D metama­te­ri­als", the group of researchers lead by Hector Fellow Martin Wegener explains how rotons may be observed without quantum effects under normal ambient condi­tions and at almost freely selec­table frequen­cies or wavelengths with the help of metama­te­ri­als. In the future, his could make it possi­ble to better manip­u­late acoustic waves in air or in materi­als, for example, to reflect them back, redirect them or gener­ate echoes.

Congrat­u­la­tions to Martin Wegener!