Jan’s Publications

@article{WOS:000336740900001,

title = {BCS instabilities of electron stars to holographic superconductors},

author = {Yan Liu and Koenraad Schalm and Ya-Wen Sun and Jan Zaanen},

doi = {10.1007/JHEP05(2014)122},

issn = {1029-8479},

year  = {2014},

date = {2014-05-01},

journal = {JOURNAL OF HIGH ENERGY PHYSICS},

number = {5},

publisher = {SPRINGER},

address = {233 SPRING ST, NEW YORK, NY 10013 USA},

abstract = {We study fermion pairing and condensation towards an ordered state in 

 strongly coupled quantum critical systems with a holographic AdS/CFT 

 dual. On the gravity side this is modeled by a system of charged fermion 

 interacting through a BCS coupling. At finite density such a system has 

 a BCS instability. We combine the relativistic version of mean-field BCS 

 with the semi-classical fluid approximation for the many-body state of 

 fermions. The resulting groundstate is the AdS equivalent of a charged 

 neutron star with a superconducting core. The spectral function of the 

 fermions confirms that the ground state is ordered through the 

 condensation of the pair operator. A natural variant of the BCS star is 

 shown to exist where the gap field couples Stueckelberg-like to the AdS 

 Maxwell field. This enhances the tendency of the system to superconduct.},

keywords = {Holography and condensed matter physics (AdS/CMT); Gauge-gravity   correspondence},

pubstate = {published},

tppubtype = {article}

}

@article{WOS:000325565300002,

title = {Bose-Fermi competition in holographic metals},

author = {Yan Liu and Koenraad Schalm and Ya-Wen Sun and Jan Zaanen},

doi = {10.1007/JHEP10(2013)064},

issn = {1029-8479},

year  = {2013},

date = {2013-10-01},

journal = {JOURNAL OF HIGH ENERGY PHYSICS},

number = {10},

publisher = {SPRINGER},

address = {ONE NEW YORK PLAZA, SUITE 4600, NEW YORK, NY, UNITED STATES},

abstract = {We study the holographic dual of a finite density system with both 

 bosonic and fermionic degrees of freedom. There is no evidence for a 

 universal bose-dominated ground state. Instead, depending on the 

 relative conformal weights the preferred groundstate is either pure 

 AdS-Reissner-Nordstrom, a holographic superconductor, an electron star, 

 or a novel mixed state that is best characterized as a hairy electron 

 star.},

keywords = {Holography and condensed matter physics (AdS/CMT); Gauge-gravity   correspondence},

pubstate = {published},

tppubtype = {article}

}

@article{WOS:000310851800031,

title = {Lattice potentials and fermions in holographic non Fermi-liquids: 

 hybridizing local quantum criticality},

author = {Yan Liu and Koenraad Schalm and Ya-Wen Sun and Jan Zaanen},

doi = {10.1007/JHEP10(2012)036},

issn = {1029-8479},

year  = {2012},

date = {2012-10-01},

journal = {JOURNAL OF HIGH ENERGY PHYSICS},

number = {10},

publisher = {SPRINGER},

address = {233 SPRING ST, NEW YORK, NY 10013 USA},

abstract = {We study lattice effects in strongly coupled systems of fermions at a 

 finite density described by a holographic dual consisting of fermions in 

 Anti-de-Sitter space in the presence of a Reissner-Nordstrom black hole. 

 The lattice effect is encoded by a periodic modulation of the chemical 

 potential with a wavelength of order of the intrinsic length scales of 

 the system. This corresponds with a highly complicated ``band 

 structure'' problem in AdS, which we only manage to solve in the weak 

 potential limit. The ``domain wall'' fermions in AdS encoding for the 

 Fermi surfaces in the boundary field theory diffract as usually against 

 the periodic lattice, giving rise to band gaps. However, the deep 

 infrared of the field theory as encoded by the near horizon AdS(2) 

 geometry in the bulk reacts in a surprising way to the weak potential. 

 The hybridization of the fermions bulk dualizes into a linear 

 combination of CFT1 ``local quantum critical'' propagators in the 

 bulk, characterized by momentum dependent exponents displaced by lattice 

 Umklapp vectors. This has the consequence that the metals showing 

 quasi-Fermi surfaces cannot be localized in band insulators. In the 

 AdS(2) metal regime, where the conformal dimension of the fermionic 

 operator is large and no Fermi surfaces are present at low T/mu, the 

 lattice gives rise to a characteristic dependence of the energy scaling 

 as a function of momentum. We predict crossovers from a high energy 

 standard momentum AdS(2) scaling to a low energy regime where exponents 

 found associated with momenta ``backscattered'' to a lower Brillioun 

 zone in the extended zone scheme. We comment on how these findings can 

 be used as a unique fingerprint for the detection of AdS(2) like 

 ``pseudogap metals'' in the laboratory.},

keywords = {Holography and condensed matter physics (AdS/CMT); Gauge-gravity   correspondence},

pubstate = {published},

tppubtype = {article}

}