Publications

The superconducting gap in high-Tc cuprates is known to exhibit spatial inhomogeneity. It is unknown however, how disorder of the superconducting gap translates to disorder of the superconducting phase. To address this question we developed 2-D terahertz spectroscopy in a non-collinear geometry for the first time, allowing us to study interlayer tunneling nonlinearities in single-crystal LSCO.

A Liu, D Pavicevic, MH Michael, AG Salvador, PE Dolgirev, M Fechner, AS Disa, PM Lozano, Q Li, GD Gu, E Demler, and A Cavalleri

Nature Physics, 20, 1751–1756 (2024)

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In open quantum systems, coupling between system and bath degrees of freedom are a primary source of quantum decoherence. Multidimensional coherent spectroscopy (MDCS) is a powerful technique capable of directly probing the spectral density of the system–bath coupling. To simplify modeling of MDCS of an open quantum system, we derive a compact, exact expression for multidimensional spectra of a spin-boson Hamiltonian.

A Liu.

Advanced Quantum Technologies 7, 3 (2024)

YTiO3 is a low-temperature ferromagnet in which orbital fluctuations lower the Curie temperature. Here, we used a strong-field terahertz light field to resonantly excite a vibrational mode that results in a remarkable threefold increase in the Curie temperature. This effect is attributed to a light-induced suppression of orbital fluctuations that manifests as metastable ferromagnetism persisting for nanoseconds.

AS Disa, J Curtis, M Fechner, A Liu, A von Hoegen, M Forst, TF Nova, P Narang, A Maljuk, AV Boris, B Keimer, and A Cavalleri

Nature 617, 7959 (2023)

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Colloidal nanoplatelets are often claimed to be homogeneously broadened due to the dominant out-of-plane quantum confinement. To validate this claim we use 2-D spectroscopy to simultaneously resolve homogeneous and inhomogeneous exciton linewidths in CsPbI3 perovskite nanoplatelets. These linewidths are resolved as a function of temperature, excitation power, and exciton resonance energy to provide design criteria for engineering optoelectronic properties for applications.

A Liu, G Nagamine, LG Bonato, DB Almeida, LF Zagonel, AF Nogueira, LA Padilha, and ST Cundiff.

ACS Nano 15, 4 (2021)

The exciton manifold in lead-halide perovskite nanocrystals is claimed to host “bright-triplet” excitons that contribute to their remarkable luminescence efficiencies. However, signatures of these bright-triplet excitons are normally obscured by dominant inhomogeneous broadening. To circumvent this issue, we use polarization-resolved 2-D spectroscopy to extract the intrinsic exciton lineshape in an ensemble and find evidence of an interleaved “partially-bright” exciton manifold.

A Liu, DB Almeida, LG Bonato, G Nagamine, LF Zagonel, AF Nogueira, LA Padilha, and ST Cundiff.

Science Advances 7, 1 (2021)

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The spectral density of exciton-phonon coupling is a quantity that is difficult to measure directly. We apply 2-D spectroscopy at cryogenic temperatures to resolve the spectral density in CdSe colloidal quantum dots, which in turn reveals confined vibrational modes from the nanometer-size dot geometry.

A Liu, DB Almeida, W-K Bae, LA Padilha, and ST Cundiff.

Journal of Physical Chemistry Letters 10, 20 (2019)