TY - JOUR
KW - electron-phonon coupling
KW - phase transition
KW - quantum materials
KW - thermal equilibrium
AU - Xun Shi
AU - Wenjing You
AU - Yingchao Zhang
AU - Zhensheng Tao
AU - Peter Oppeneer
AU - Xianxin Wu
AU - Ronny Thomale
AU - Kai Rossnagel
AU - Michael Bauer
AU - Henry Kapteyn
AU - Margaret Murnane
AB - Quantum materials represent one of the most promising frontiers in the quest for faster, lightweight, energy-efficient technologies. However, their inherent complexity and rich phase landscape make them challenging to understand or manipulate. Here, we present a new ultrafast electron calorimetry technique that can systematically uncover new phases of quantum matter. Using time- and angle-resolved photoemission spectroscopy, we measure the dynamic electron temperature, band structure, and heat capacity. This approach allows us to uncover a new long-lived metastable state in the charge density wave material 1<em>T</em>-TaSe<sup>2</sup>, which is distinct from all the known equilibrium phases: It is characterized by a substantially reduced effective total heat capacity that is only 30\% of the normal value, because of selective electron-phonon coupling to a subset of phonon modes. As a result, less energy is required to melt the charge order and transform the state of the material than under thermal equilibrium conditions.
BT - Science Advances
DA - 2019-03
DO - 10.1126/sciadv.aav4449
IS - 3
N2 - Quantum materials represent one of the most promising frontiers in the quest for faster, lightweight, energy-efficient technologies. However, their inherent complexity and rich phase landscape make them challenging to understand or manipulate. Here, we present a new ultrafast electron calorimetry technique that can systematically uncover new phases of quantum matter. Using time- and angle-resolved photoemission spectroscopy, we measure the dynamic electron temperature, band structure, and heat capacity. This approach allows us to uncover a new long-lived metastable state in the charge density wave material 1<em>T</em>-TaSe<sup>2</sup>, which is distinct from all the known equilibrium phases: It is characterized by a substantially reduced effective total heat capacity that is only 30\% of the normal value, because of selective electron-phonon coupling to a subset of phonon modes. As a result, less energy is required to melt the charge order and transform the state of the material than under thermal equilibrium conditions.
PY - 2019
EP - eaav4449
T2 - Science Advances
TI - Ultrafast electron calorimetry uncovers a new long-lived metastable state in 1T-TaSe2 mediated by mode-selective electron-phonon coupling
UR - http://advances.sciencemag.org/content/5/3/eaav4449
VL - 5
ER -