Development and Construction of 2D THz spectroscopy for the measurement of quantum correlated systems
Abstract
This proposal concerns the development of a new kind of spectrometer for characterization of materials with interesting quantum mechanical correlations. Quantum materials as such are one of the most interesting areas of modern condensed matter physics. Strong interactions and topological effects conspire to give novel material properties that have no precedent. They are likely to find use in the next generation of devices. The science pursued in the context of this research will enable these advances. However, despite the overwhelming interest in these systems, it is increasingly clear that we do not have the experimental tools to properly characterize many of their properties. For instance, one of the most notable aspects of many topological spin systems is that they possess "fractionalized" particles. In such systems, the conventional particles and excitations of the material fractionalize into multiple parts. In 1D this fractionalization is quite natural, but in higher dimensional "spin-liquids" it is controversial. However even in 1D, we do not have the proper techniques to measure many of the properties of fractionalized particles and manipulate them. In conventional linear spectroscopy, we measure only broad "continuum" lineshapes in candidate systems that prevent the direct detection of individual particles and obscure their properties if they exist. In this regard, I propose that the new technique of 2D-THz spectroscopy may give unique insight into many of these material systems. 2D-THz spectroscopy is a "pump" and "probe" techniques in which sequential THz pulses will be used to interrogate the non-linear response of materials. In 2D spectroscopy in general, one excites the system at one frequency, probes at another, and ultimately plots a 2D spectrum of the response along excitation and probe frequency axes. However, unlike most pump-probe measurements the system is excited coherently and so one can discriminate homogeneous and inhomogeneous broadenings and explicitly probe the couplings between excitations. It its optical and NMR versions it has revolutionized the study of electronic and vibrational couplings in solids, liquids, biological and molecular systems. Nonlinear two-dimensional (2D) spectroscopy in the ultrafast time domain has also become an essential tool for unravelling the dynamics and couplings of elementary excitations in condensed-phase systems. The realization of 2D spectroscopy in the THz regime is made possible by the recent development of high-intensity THz pulses in a tabletop setting. The development of 2D-THz will be the development of what is essentially a form of THz range electron spin resonance. For materials that show fractionalized particles, I believe 2D-THz will function as a unique probe of these fractional particles in topological spin-liquid systems and will be able to explicitly demonstrate the existence of these particles and their properties. The anti-diagonal width will be a measure of the two spinon state lifetime. The technique will also be able to give unique insight into electron-phonon couplings, electron-magnon couplings, measure intrinsically quantum mechanical entanglement properties between quasiparticles, measure Bogoliubon lifetimes in superconductors, and measure relaxation phenomena in structural and electronic glasses. These aspects of fundamental science are ones of great technical opportunity in areas of interest to the Army Research Office (ARO). However it is important to point out that the goal is to implement a general technique that will have broad applicability to many problems in condensed matter physics.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810201
Entities
People
- Peter Armitage
Organizations
- Army Contracting Command
- Johns Hopkins University
- United States Army