Femtosecond terahertz dynamics of cooperative transitions: from charge density waves to polariton condensates

Many-body correlation effects in complex quantum systems often lead to phase transitions that bear great technological potential. However, the underlying microscopic driving mechanisms or even the quantum-mechanical properties of the novel ground state often remain elusive. Here we employ phase-locked ultrabroadband terahertz (THz) pulses to disentangle two coexisting orders in the charge density wave phase 1T-TiSe2 via their individual non-equilibrium multi- THz dynamics. Furthermore, we demonstrate that few-cycle THz pulses can project out the matter part of a transient cold exciton-polariton condensate, providing novel insights into the very nature of this macroscopic quantum state.

[1]  Michael Bauer,et al.  Collapse of long-range charge order tracked by time-resolved photoemission at high momenta , 2011, Nature.

[2]  Qing’an Li,et al.  Chiral phase transition in charge ordered 1T-TiSe2. , 2012, Physical review letters.

[3]  S. Johnson,et al.  Nonthermal melting of a charge density wave in TiSe2. , 2011, Physical review letters.

[4]  Semimetal-to-semimetal charge density wave transition in 1T-TiSe(2). , 2007, Physical review letters.

[5]  Rupert Huber,et al.  Stimulated terahertz emission from intraexcitonic transitions in Cu2O. , 2006, Physical review letters.

[6]  Gregor Weihs,et al.  Condensation of Semiconductor Microcavity Exciton Polaritons , 2002, Science.

[7]  Rupert Huber,et al.  Shot noise reduced terahertz detection via spectrally postfiltered electro-optic sampling. , 2014, Optics letters.

[8]  S. Koch,et al.  Terahertz coherent control of optically dark paraexcitons in Cu2O. , 2008, Physical review letters.

[9]  R. Bratschitsch,et al.  Resonant internal quantum transitions and femtosecond radiative decay of excitons in monolayer WSe2. , 2015, Nature materials.

[10]  J. V. Wezel,et al.  Exciton-phonon-driven charge density wave in TiSe 2 , 2010 .

[11]  C. Battaglia,et al.  Spontaneous exciton condensation in 1T-TiSe2: BCS-like approach , 2008, 0809.1930.

[12]  M. Chou,et al.  Charge density wave transition in single-layer titanium diselenide , 2015, Nature Communications.

[13]  D. Chemla,et al.  Ultrafast terahertz probes of transient conducting and insulating phases in an electron–hole gas , 2003, Nature.

[14]  Microcavity design for low threshold polariton condensation with ultrashort optical pulse excitation , 2015, 1605.04891.

[15]  A. Kavokin,et al.  Propagation and amplification dynamics of 1D polariton condensates. , 2012, Physical review letters.

[16]  A. Lemaître,et al.  Revealing the dark side of a bright exciton–polariton condensate , 2014, Nature Communications.

[17]  Elbio Dagotto,et al.  Complexity in Strongly Correlated Electronic Systems , 2005, Science.

[18]  F. Tauser,et al.  How many-particle interactions develop after ultrafast excitation of an electron–hole plasma , 2001, Nature.

[19]  L. Kipp,et al.  Charge-density-wave phase transition in 1 T − TiSe 2 : Excitonic insulator versus band-type Jahn-Teller mechanism , 2002 .

[20]  R Huber,et al.  Non-thermal separation of electronic and structural orders in a persisting charge density wave. , 2014, Nature materials.

[21]  M. Klein,et al.  Raman and infrared studies of superlattice formation in TiSe 2 , 1977 .

[22]  V. Savona,et al.  Bose–Einstein condensation of exciton polaritons , 2006, Nature.