Multidimensional entropy landscape of quantum criticality

The Third Law of Thermodynamics states that the entropy of any system in equilibrium has to vanish at absolute zero temperature. At nonzero temperatures, on the other hand, matter is expected to accumulate entropy near a quantum critical point (QCP), where it undergoes a continuous transition from one ground state to another. Here, we determine, based on general thermodynamic principles, the spatial-dimensional profile of the entropy S near a QCP and its steepest descent in the corresponding multidimensional stress space. We demonstrate this approach for the canonical quantum critical compound CeCu6-xAux near its onset of antiferromagnetic order. We are able to link the directional stress dependence of S to the previously determined geometry of quantum critical fluctuations. Our demonstration of the multidimensional entropy landscape provides the foundation to understand how quantum criticality nucleates novel phases such as high-temperature superconductivity.Comment: 14 pages, 4 figure

Observation of Buried Phosphorus Dopants near Clean Si(100)-(2x1) with Scanning Tunneling Microscopy

We have used scanning tunneling microscopy to identify individual phosphorus dopant atoms near the clean silicon (100)-(2x1) reconstructed surface. The charge-induced band bending signature associated with the dopants shows up as an enhancement in both filled and empty states and is consistent with the appearance of n-type dopants on compound semiconductor surfaces and passivated Si(100)-(2x1). We observe dopants at different depths and see a strong dependence of the signature on the magnitude of the sample voltage. Our results suggest that, on this clean surface, the antibonding surface state band acts as an extension of the bulk conduction band into the gap. The positively charged dimer vacancies that have been observed previously appear as depressions in the filled states, as opposed to enhancements, because they disrupt these surface bands.Comment: 4 pages, 3 figures. TeX for OSX from Wierde

On Excess Compensation Earned by Underwriters in Firm Commitment Initial Public Offerings of Common Stock: An Empirical Analysis

This paper examines compensation for the underwriting activity in firm commitment initial public offerings (IPOs) of common stock in the U.S. When compensation for origination, management and marketing efforts are excluded from total underwriter compensation, we find that the portion of the total compensation assigned for the underwriting activity itself exceeds theoretical compensation only for issues that sell out very quickly. We interpret this finding as empirical evidence supporting the incentive for underwriters to underprice IPOs. Finally, we find excess compensation to underwriters is positively related to the riskiness of the IPO and negatively related to the degree of competition among investment bankers and the size of the IPO

Magnetic and structural quantum phase transitions in CeCu6-xAux are independent

The heavy-fermion compound CeCu$_{6-x}$Au$_x$ has become a model system for unconventional magnetic quantum criticality. For small Au concentrations $0 \leq x < 0.16$, the compound undergoes a structural transition from orthorhombic to monoclinic crystal symmetry at a temperature $T_{s}$ with $T_{s} \rightarrow 0$ for $x \approx 0.15$. Antiferromagnetic order sets in close to $x \approx 0.1$. To shed light on the interplay between quantum critical magnetic and structural fluctuations we performed neutron-scattering and thermodynamic measurements on samples with $0 \leq x\leq 0.3$. The resulting phase diagram shows that the antiferromagnetic and monoclinic phase coexist in a tiny Au concentration range between $x\approx 0.1$ and $0.15$. The application of hydrostatic and chemical pressure allows to clearly separate the transitions from each other and to explore a possible effect of the structural transition on the magnetic quantum critical behavior. Our measurements demonstrate that at low temperatures the unconventional quantum criticality exclusively arises from magnetic fluctuations and is not affected by the monoclinic distortion.Comment: 5 pages, 3 figure

Prospectus, September 8, 2010

UNEMPLOYMENT CREATES NEW ROLE, AND PAIN, FOR COMMUNITY COLLEGES; Poll: Obama\u27s appeal slides in Illinois; Chuck Shepherd\u27s News of the Weird; Album Review: Ra Ra Riot\u27s The Orchard; Parkland teacher feature: Kim Pankau; Not to fear, help is here!; Unemployment, and my new car; Reason for optimism in Mideast talks; He\u27s baaack : More Students Are Moving Back With Their Parents After Graduation; Businesses see advantage in green buildings; Student Government; Leafmaniahttps://spark.parkland.edu/prospectus_2010/1021/thumbnail.jp

Prospectus, October 27, 2010

GIVING FUTURE GENERATIONS A CHANCE TO LEARN; The College Students Guide to Statewide Elections; Chuck Shepherd\u27s News of the Weird; The Perfect Soundtrack for Your Halloween Party; The Origin of Halloween; What Should You do This Halloween?; A Trend That is Taking Over Faster Thank Skinny Jeans: Kindness; Skinny Celebrity Chefs Can\u27t be Trusted; Zuckerberg Left With Plenty of Success, but Not Many Friends : Facebook Creator Shown as More than a Computer Genius in New Film, The Social Network; How to Stay Safe This Halloween Weekend; Former Parkland Instructor Wins Gold Medal; Nebraska Brings Tradition to Big Ten Table; In Search of Spiritshttps://spark.parkland.edu/prospectus_2010/1027/thumbnail.jp

Prospectus, January 26, 2011

DRIVERS BEWARE!; Is bigger always better?; New fitness center plans shaping up; Chuck Shepherd\u27s News of the Weird; Album Review: Ben Folds and Nick Hornby\u27s Lonely Avenue; DREAM Act poster child stirs controversy; Study: Many students not thinking critically; Health care, one more time; The best little-known planetarium in Illinois; Moore than just a teacher - Behind the scenes with John Moore; Prospectus Pick: Shock Totem; Bonus Stage! The official Prospectus gaming column; Lady Cobras improve streak to 8; State of the Art 2011https://spark.parkland.edu/prospectus_2011/1025/thumbnail.jp

Prospectus, December 8, 2010

THE UNITED STATES DRAFT AND YOU; Looking out for college students; Spirituality finds a home at college; Chuck Shepherd\u27s News of the Weird; Eminem gets 10 Grammy nominations; Remember, its the thought that counts; Parkland Theatre presents: Nuncrackers: Bringing a whole lotta\u27 Nunsense to the community; Decoding Your Final Exam; America\u27s young scientists at risk; 5 ways to avoid family during the holidays; How to survive the winter; Prospectus Pick: Halford III: Winter Songs; Harry Potter\u27s magic brings full house to local theaters; Ask MNN: Is it better to idle or turn your car off?; Gadgets: Headphones, gear to haul your gadgets, a do-it-all printer and a book on best apps; A guide to events over holiday break; Starting teens on plastic can be costly; Cobra Men\u27s winning streak hits 5 with pair of wins; Cobra athletics food drive; #10 Parkland Women surprise #6 Lake Land; Access Success: Meteorologist Jennifer Ketchmark; A dying trend: Holiday movieshttps://spark.parkland.edu/prospectus_2010/1032/thumbnail.jp